Function.prototype.toString() - JavaScript
le is stored in a github repository. if you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request. syntax function.tostring() return value a string representing the source code of the function. ...
...t object.prototype.tostring. for user-defined function objects, the tostring method returns a string containing the source text segment which was used to define the function. javascript calls the tostring method automatically when a function is to be represented as a text value, e.g. when a function is concatenated with a string. the tostring() method will throw a typeerror exception ("function.prototype.tostring called on incompatible object"), if its this value object is not a function object. ...
...he source text segment which was used to define the function. javascript calls the tostring method automatically when a function is to be represented as a text value, e.g. when a function is concatenated with a string. the tostring() method will throw a typeerror exception ("function.prototype.tostring called on incompatible object"), if its this value object is not a function object. ...
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handler.setPrototypeOf() - JavaScript
the handler.setprototypeof() method is a trap for object.setprototypeof(). the source for this interactive example is stored in a github repository. if you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request. syntax const p = new proxy(target, { setprototypeof: function(target, prototype) { } }); parameters the following parameters are passed to the setprototypeof() method. this is bound to the handler. target the target object. prototype the object's new prototype or null. return value the setprototypeof() method returns true if the [[prototype]] was successfully changed, otherwise false. description the handler.setprototypeof() method is a trap for object.setprototypeof(). intercepti...
...() method. this is bound to the handler. target the target object. prototype the object's new prototype or null. return value the setprototypeof() method returns true if the [[prototype]] was successfully changed, otherwise false. description the handler.setprototypeof() method is a trap for object.setprototypeof(). interceptions this trap can intercept these operations: object.setprototypeof() reflect.setprototypeof() invariants if the following invariants are violated, the proxy will throw a typeerror: if target is not extensible, the prototype parameter must be the same value as object.getprototypeof(target). ...
...a trap for object.setprototypeof(). interceptions this trap can intercept these operations: object.setprototypeof() reflect.setprototypeof() invariants if the following invariants are violated, the proxy will throw a typeerror: if target is not extensible, the prototype parameter must be the same value as object.getprototypeof(target). examples if you want to disallow setting a new prototype for your object, your handler's setprototypeof() method can either return false, or it can throw an exception. approach 1: returning false this approach means that any mutating operation that throws an exception on failure to mutate, must create the exception itself. for example, object.setprototypeof() will create and throw a typeerror itself. if the mutation is performed by an operation tha...
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TypedArray.prototype.fill() - JavaScript
typedarray is one of the typed array types here. the source for this interactive example is stored in a github repository. if you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request. syntax typedarray.fill(value[, start = 0[, end = this.length]]) parameters value value to fill the typed array with. start optional. start index. defaults to 0. end optional. ...
...end arguments are optional with default values of 0 and the length of the this object. if start is negative, it is treated as length+start where length is the length of the array. if end is negative, it is treated as length+end. polyfill since there is no global object with the name typedarray, polyfilling must be done on an "as needed" basis. ...
...bject. if start is negative, it is treated as length+start where length is the length of the array. if end is negative, it is treated as length+end. polyfill since there is no global object with the name typedarray, polyfilling must be done on an "as needed" basis. use the following "polyfill" along with the array.prototype.fill() polyfill. ...
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JS_LinkConstructorAndPrototype
this article covers features introduced in spidermonkey 17 set up ctor.prototype = proto and proto.constructor = ctor with the right property flags. syntax bool js_linkconstructorandprototype(jscontext *cx, js::handle<jsobject*> ctor, js::handle<jsobject*> proto); name type description cx jscontext * pointer to a js context from which to derive runtime information. requires request. in a js_threadsafe build, the caller must be in a request on this jscontext. ctor js::handle&lt;jsobject*&gt; pointer to the constructor object. proto js::handle&lt;jsobject*&gt; pointer to the prototype object. ...
...on cx jscontext * pointer to a js context from which to derive runtime information. requires request. in a js_threadsafe build, the caller must be in a request on this jscontext. ctor js::handle&lt;jsobject*&gt; pointer to the constructor object. proto js::handle&lt;jsobject*&gt; pointer to the prototype object. ...
...scontext * pointer to a js context from which to derive runtime information. requires request. in a js_threadsafe build, the caller must be in a request on this jscontext. ctor js::handle&lt;jsobject*&gt; pointer to the constructor object. proto js::handle&lt;jsobject*&gt; pointer to the prototype object. ...
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JS_SetPrototype
set a javascript object's prototype. syntax bool js_setprototype(jscontext *cx, js::handleobject obj, js::handleobject proto); name type description cx jscontext * the context in which to set the object's prototype. requires request. in a js_threadsafe build, the caller must be in a request on this jscontext. obj js::handleobject the object to modify. proto js::handleobject the object to set as the new prototype of obj. description js_setprototype sets the prototype object for a specified object. a prototype object provides properties that are shared by similar js object instances. ...
...adsafe build, the caller must be in a request on this jscontext. obj js::handleobject the object to modify. proto js::handleobject the object to set as the new prototype of obj. description js_setprototype sets the prototype object for a specified object. a prototype object provides properties that are shared by similar js object instances. ordinarily you set a prototype for an object when you create the object with js_newobject, but if you do not set a prototype at that time, you can later call js_setprototype to do so. obj is a pointer to an existing js object, and proto is a pointer to second existing object upon which the first object is to be based. on success, js_setprototype returns true. otherwise it returns false. take care not to create a circularly-lin...
...ct when you create the object with js_newobject, but if you do not set a prototype at that time, you can later call js_setprototype to do so. obj is a pointer to an existing js object, and proto is a pointer to second existing object upon which the first object is to be based. on success, js_setprototype returns true. otherwise it returns false. take care not to create a circularly-linked list of prototypes using this function, because such a set of prototypes cannot be resolved by the javascript engine and can easily lead to an infinite loop. ...
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TypeError: X.prototype.y called on incompatible type - JavaScript
the javascript exception "called on incompatible target (or object)" occurs when a function (on a given object), is called with a this not corresponding to the type expected by the function. ...
... the javascript exception "called on incompatible target (or object)" occurs when a function (on a given object), is called with a this not corresponding to the type expected by the function. ...
...on "called on incompatible target (or object)" occurs when a function (on a given object), is called with a this not corresponding to the type expected by the function. ...
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Array.prototype.forEach() - JavaScript
e is to execute side effects at the end of a chain. foreach() does not mutate the array on which it is called. (however, callback may do so) there is no way to stop or break a foreach() loop other than by throwing an exception. if you need such behavior, the foreach() method is the wrong tool. early termination may be accomplished with: a simple for loop a for...of / for...in loops array.prototype.every() array.prototype.some() array.prototype.find() array.prototype.findindex() array methods: every(), some(), find(), and findindex() test the array elements with a predicate returning a truthy value to determine if further iteration is required. foreach expects a synchronous function foreach does not wait for promises. kindly make sure you are aware of the implications while using pr...
...onsole.log('a[' + index + '] = ' + element) } // notice that index 2 is skipped, since there is no item at // that position in the array... [2, 5, , 9].foreach(logarrayelements) // logs: // a[0] = 2 // a[1] = 5 // a[3] = 9 using thisarg the following (contrived) example updates an object's properties from each entry in the array: function counter() { this.sum = 0 this.count = 0 } counter.prototype.add = function(array) { array.foreach((entry) => { this.sum += entry ++this.count }, this) // ^---- note } const obj = new counter() obj.add([2, 5, 9]) obj.count // 3 obj.sum // 16 since the thisarg parameter (this) is provided to foreach(), it is passed to callback each time it's invoked. the callback uses it as its this value. note: if passing the callback function uses an ar...
...s it as its this value. note: if passing the callback function uses an arrow function expression, the thisarg parameter can be omitted, since all arrow functions lexically bind the this value. an object copy function the following code creates a copy of a given object. there are different ways to create a copy of an object. ...
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Array.prototype.indexOf() - JavaScript
rom front to back. if the provided index is 0, then the whole array will be searched. default: 0 (entire array is searched). return value the first index of the element in the array; -1 if not found. description indexof() compares searchelement to elements of the array using strict equality (the same method used by the === or triple-equals operator). note: for the string method, see string.prototype.indexof(). polyfill indexof() was added to the ecma-262 standard in the 5th edition; as such it may not be present in all browsers. you can work around this by utilizing the following code at the beginning of your scripts. this will allow you to use indexof() when there is still no native support. this algorithm matches the one specified in ecma-262, 5th edition, assuming typeerror and math.a...
...l no native support. this algorithm matches the one specified in ecma-262, 5th edition, assuming typeerror and math.abs() have their original values. // this version tries to optimize by only checking for "in" when looking for undefined and // skipping the definitely fruitless nan search. other parts are merely cosmetic conciseness. // whether it is actually faster remains to be seen. ...
...lgorithm matches the one specified in ecma-262, 5th edition, assuming typeerror and math.abs() have their original values. // this version tries to optimize by only checking for "in" when looking for undefined and // skipping the definitely fruitless nan search. other parts are merely cosmetic conciseness. // whether it is actually faster remains to be seen. ...
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Array.prototype.toLocaleString() - JavaScript
se strings are separated by a locale-specific string (such as a comma “,”). syntax arr.tolocalestring([locales[, options]]); parameters locales optional a string with a bcp 47 language tag, or an array of such strings. for the general form and interpretation of the locales argument, see the intl page. options optional an object with configuration properties, for numbers see number.prototype.tolocalestring(), and for dates see date.prototype.tolocalestring(). return value a string representing the elements of the array. polyfill // https://tc39.github.io/ecma402/#sup-array.prototype.tolocalestring if (!array.prototype.tolocalestring) { object.defineproperty(array.prototype, 'tolocalestring', { value: function(locales, options) { // 1. let o be ? toobject(this value)...
... '' : nextelement.tolocalestring(locales, options); // e. let r be a string value produced by // concatenating s and r. r = s + r; // f. increase k by 1. k++; } // 10. return r. ...
... } // 10. return r. return r; } }); } if you need to support truly obsolete javascript engines that don't support object.defineproperty, it's best not to polyfill array.prototype methods at all, as you can't make them non-enumerable. examples using locales and options the elements of the array are converted to strings using their tolocalestring methods. ...
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Object.prototype.toLocaleString() - JavaScript
thub.com/mdn/interactive-examples and send us a pull request. syntax obj.tolocalestring() return value a string representing the object. description object's tolocalestring returns the result of calling tostring(). this function is provided to give objects a generic tolocalestring method, even though not all may use it. see the list below. ...
...us a pull request. syntax obj.tolocalestring() return value a string representing the object. description object's tolocalestring returns the result of calling tostring(). this function is provided to give objects a generic tolocalestring method, even though not all may use it. see the list below. ...
...estring() return value a string representing the object. description object's tolocalestring returns the result of calling tostring(). this function is provided to give objects a generic tolocalestring method, even though not all may use it. see the list below. ...
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Object.prototype.__noSuchMethod__ - Archive of obsolete content
sn't exist on an object results in a typeerror being thrown. this behavior can be circumvented by defining a function at that object's __nosuchmethod__ member. the function takes two arguments, the first is the name of the method attempted and the second is an array of the arguments that were passed in the method call. the second argument is an actual array (that is, it inherits through the array.prototype chain) and not the array-like arguments object. if this method cannot be called, either as if undefined by default, if deleted, or if manually set to a non-function, the javascript engine will revert to throwing typeerrors. examples simple test of __nosuchmethod__ var o = { __nosuchmethod__: function(id, args) { console.log(id, '(' + args.join(', ') + ')'); ...
...a parent for multiple inheritance function addparent(obj, parent) { // if the object isn't initialized, initialize it if (!obj.__parents_) { obj.__parents_ = []; obj.__nosuchmethod__ = nomethod; } // add the parent obj.__parents_.push(parent); } an example of using this idea is shown below. // example base class 1 function namedthing(name) { this.name = name; } namedthing.prototype = { getname: function() { return this.name; }, setname: function(newname) { this.name = newname; } } // example base class 2 function agedthing(age) { this.age = age; } agedthing.prototype = { getage: function() { return this.age; }, setage: function(age) { this.age = age; } } // child class. inherits from namedthing and agedthing // as well as defining address function person(name, ...
...e; }, setname: function(newname) { this.name = newname; } } // example base class 2 function agedthing(age) { this.age = age; } agedthing.prototype = { getage: function() { return this.age; }, setage: function(age) { this.age = age; } } // child class. ...
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Array.prototype.reduce() - JavaScript
third call 11 2 2 [0, 1, 2, 3, 4] 13 fourth call 13 3 3 [0, 1, 2, 3, 4] 16 fifth call 16 4 4 [0, 1, 2, 3, 4] 20 the value returned by reduce() in this case would be 20. ...
... 2 [0, 1, 2, 3, 4] 13 fourth call 13 3 3 [0, 1, 2, 3, 4] 16 fifth call 16 4 4 [0, 1, 2, 3, 4] 20 the value returned by reduce() in this case would be 20. polyfill // production steps of ecma-262, edition 5, 15.4.4.21 // reference: http://es5.github.io/#x15.4.4.21 // https://tc39.github.io/ecma262/#sec-array.prototype.reduce if (!array.prototype.reduce) { object.defineproperty(array.prototype, 'reduce', { value: function(callback /*, initialvalue*/) { if (this === null) { throw new typeerror( 'array.prototype.reduce ' + 'called on null or undefined' ); } if (typeof callback !== 'function') { throw new typeerror( callback + ' is not a function'); } // 1. let o be ? t...
... // « accumulator, kvalue, k, o »). if (k in o) { value = callback(value, o[k], k, o); } // d. increase k by 1. k++; } // 9. return accumulator. return value; } }); } caution: if you need to support truly obsolete javascript engines that do not support object.defineproperty(), it is best not to polyfill array.prototype methods at all, as you cannot make them non-enumerable. examples sum all the values of an array let sum = [0, 1, 2, 3].reduce(function (accumulator, currentvalue) { return accumulator + currentvalue }, 0) // sum is 6 alternatively written with an arrow function: let total = [ 0, 1, 2, 3 ].reduce( ( accumulator, currentvalue ) => accumulator + currentvalue, 0 ) sum of values in an o...
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Array.prototype.reduceRight() - JavaScript
the reduceright() method applies a function against an accumulator and each value of the array (from right-to-left) to reduce it to a single value. the source for this interactive example is stored in a github repository. if you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request. see also array.prototype.reduce() for left-to-right. syntax arr.reduceright(callback(accumulator, currentvalue[, index[, array]])[, initialvalue]) parameters callback function to execute on each value in the array, taking four arguments: accumulator the value previously returned in the last invocation of the callback, or initialvalue, if supplied. (see below.) currentvalue the current element being processed in ...
...ard in the 5th edition; as such it may not be present in all implementations of the standard. you can work around this by inserting the following code at the beginning of your scripts, allowing use of reduceright in implementations which do not natively support it. ...
...t may not be present in all implementations of the standard. you can work around this by inserting the following code at the beginning of your scripts, allowing use of reduceright in implementations which do not natively support it. ...
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Array.prototype.filter() - JavaScript
erefore, it may not be present in all implementations of the standard. you can work around this by inserting the following code at the beginning of your scripts, allowing use of filter() in ecma-262 implementations which do not natively support it. ...
... all implementations of the standard. you can work around this by inserting the following code at the beginning of your scripts, allowing use of filter() in ecma-262 implementations which do not natively support it. this algorithm is exactly equivalent to the one specified in ecma-262, 5th edition, assuming that fn.call evaluates to the original value of function.prototype.bind(), and that array.prototype.push() has its original value. ...
...round this by inserting the following code at the beginning of your scripts, allowing use of filter() in ecma-262 implementations which do not natively support it. this algorithm is exactly equivalent to the one specified in ecma-262, 5th edition, assuming that fn.call evaluates to the original value of function.prototype.bind(), and that array.prototype.push() has its original value. ...
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Array.prototype.find() - JavaScript
t satisfies the provided testing function. the source for this interactive example is stored in a github repository. if you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request. if you need the index of the found element in the array, use findindex(). if you need to find the index of a value, use array.prototype.indexof(). (it’s similar to findindex(), but checks each element for equality with the value instead of using a testing function.) if you need to find if a value exists in an array, use array.prototype.includes(). again, it checks each element for equality with the value instead of using a testing function. if you need to find if any element satisfies the provided testing function, use array.
....indexof(). (it’s similar to findindex(), but checks each element for equality with the value instead of using a testing function.) if you need to find if a value exists in an array, use array.prototype.includes(). again, it checks each element for equality with the value instead of using a testing function. if you need to find if any element satisfies the provided testing function, use array.prototype.some(). syntax arr.find(callback(element[, index[, array]])[, thisarg]) parameters callback function to execute on each value in the array, taking 3 arguments: element the current element in the array. index optional the index (position) of the current element in the array. array optional the array that find was called on. thisarg optional object to use as this inside ...
... begins. if an existing, yet-unvisited element of the array is changed by callback, its value passed to the callback will be the value at the time find visits that element's index. elements that are deleted are still visited. polyfill this method has been added to the ecmascript 2015 specification and may not be available in all javascript implementations yet. however, you can polyfill array.prototype.find with the following snippet: // https://tc39.github.io/ecma262/#sec-array.prototype.find if (!array.prototype.find) { object.defineproperty(array.prototype, 'find', { value: function(predicate) { // 1. let o be ? toobject(this value). if (this == null) { throw typeerror('"this" is null or not defined'); } var o = object(this); // 2. let len be ? ...
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Array.prototype.map() - JavaScript
implementations of the standard. you can work around this by inserting the following code at the beginning of your scripts, allowing use of map in implementations which do not natively support it. this algorithm is exactly the one specified in ecma-262, 5th edition, assuming object, typeerror, and array have their original values and that callback.call evaluates to the original value of function.prototype.call. // production steps of ecma-262, edition 5, 15.4.4.19 // reference: http://es5.github.io/#x15.4.4.19 if (!array.prototype.map) { array.prototype.map = function(callback/*, thisarg*/) { var t, a, k; if (this == null) { throw new typeerror('this is null or not defined'); } // 1. let o be the result of calling toobject passing the |this| // value as the argu...
...assigned from each element of the array as map loops through the original array. let numbers = [1, 4, 9] let doubles = numbers.map(function(num) { return num * 2 }) // doubles is now [2, 8, 18] // numbers is still [1, 4, 9] using map generically this example shows how to use map on a string to get an array of bytes in the ascii encoding representing the character values: let map = array.prototype.map let a = map.call('hello world', function(x) { return x.charcodeat(0) }) // a now equals [72, 101, 108, 108, 111, 32, 87, 111, 114, 108, 100] using map generically queryselectorall this example shows how to iterate through a collection of objects collected by queryselectorall. this is because queryselectorall returns a nodelist (which is a collection of objects). in this case, we return ...
..., 114, 108, 100] using map generically queryselectorall this example shows how to iterate through a collection of objects collected by queryselectorall. this is because queryselectorall returns a nodelist (which is a collection of objects). in this case, we return all the selected options' values on the screen: let elems = document.queryselectorall('select option:checked') let values = array.prototype.map.call(elems, function(obj) { return obj.value }) an easier way would be the array.from() method. tricky use case (inspired by this blog post) it is common to use the callback with one argument (the element being traversed). certain functions are also commonly used with one argument, even though they take additional optional arguments. these habits may lead to confusing behaviors. consi...
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Array.prototype.some() - JavaScript
nt in all implementations of the standard. you can work around this by inserting the following code at the beginning of your scripts, allowing use of some() in implementations which do not natively support it. ...
...s, allowing use of some() in implementations which do not natively support it. this algorithm is exactly the one specified in ecma-262, 5th edition, assuming object and typeerror have their original values and that fun.call evaluates to the original value of function.prototype.call(). ...
...in implementations which do not natively support it. this algorithm is exactly the one specified in ecma-262, 5th edition, assuming object and typeerror have their original values and that fun.call evaluates to the original value of function.prototype.call(). ...
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Array.prototype.values() - JavaScript
the values() method returns a new array iterator object that contains the values for each index in the array. syntax arr.values() return value a new array iterator object. ...
...s a new array iterator object that contains the values for each index in the array. syntax arr.values() return value a new array iterator object. examples iteration using for...of loop var arr = ['a', 'b', 'c', 'd', 'e']; var iterator = arr.values(); for (let letter of iterator) { console.log(letter); } //"a" "b" "c" "d" "e" array.prototype.values is default implementation of array.prototype[symbol.iterator]. ...
...contains the values for each index in the array. syntax arr.values() return value a new array iterator object. examples iteration using for...of loop var arr = ['a', 'b', 'c', 'd', 'e']; var iterator = arr.values(); for (let letter of iterator) { console.log(letter); } //"a" "b" "c" "d" "e" array.prototype.values is default implementation of array.prototype[symbol.iterator]. ...
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Object.prototype.hasOwnProperty() - JavaScript
roperty to test. return value a boolean indicating whether or not the object has the specified property as own property. description all descendents of object inherit the hasownproperty method. this method can be used to determine whether an object has the specified property as a direct property of that object; unlike the in operator, this method does not check for a property in the object's prototype chain. if an object is an array, hasownproperty method can check whether an index exists. note hasownproperty returns true even if the value of the property is null or undefined. o = new object(); o.propone = null; o.hasownproperty('propone'); // returns true o.proptwo = undefined; o.hasownproperty('proptwo'); // returns true examples using hasownproperty to test for a property's existe...
... hasownproperty to test for a property's existence the following example determines whether the o object contains a property named prop: o = new object(); o.hasownproperty('prop'); // returns false o.prop = 'exists'; o.hasownproperty('prop'); // returns true direct vs. inherited properties the following example differentiates between direct properties and properties inherited through the prototype chain: o = new object(); o.prop = 'exists'; o.hasownproperty('prop'); // returns true o.hasownproperty('tostring'); // returns false o.hasownproperty('hasownproperty'); // returns false iterating over the properties of an object the following example shows how to iterate over the properties of an object without executing on inherited properties. note that the for...in lo...
... ...
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Object.prototype.propertyIsEnumerable() - JavaScript
op) parameters prop the name of the property to test. return value a boolean indicating whether the specified property is enumerable and is the object's own property. description every object has a propertyisenumerable method. this method can determine whether the specified property in an object can be enumerated by a for...in loop, with the exception of properties inherited through the prototype chain. if the object does not have the specified property, this method returns false. examples a basic use of propertyisenumerable the following example shows the use of propertyisenumerable on objects and arrays: var o = {}; var a = []; o.prop = 'is enumerable'; a[0] = 'is enumerable'; o.propertyisenumerable('prop'); // returns true a.propertyisenumerable(0); // returns true user...
...ble(0); // returns true a.propertyisenumerable('length'); // returns false math.propertyisenumerable('random'); // returns false this.propertyisenumerable('math'); // returns false direct vs. ...
...propertyisenumerable('math'); // returns false direct vs. ...
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String.prototype.trimStart() - JavaScript
quest. syntax str.trimstart(); str.trimleft(); return value a new string representing the calling string stripped of whitespace from its beginning (left end). description the trimstart() / trimleft() methods return the string stripped of whitespace from its left end. trimleft() or trimstart() do not affect the value of the string itself. ...
...the trimstart() / trimleft() methods return the string stripped of whitespace from its left end. trimleft() or trimstart() do not affect the value of the string itself. aliasing for consistency with functions like string.prototype.padstart the standard method name is trimstart. however, for web compatibility reasons, trimleft remains as an alias to trimstart. ...
... aliasing for consistency with functions like string.prototype.padstart the standard method name is trimstart. however, for web compatibility reasons, trimleft remains as an alias to trimstart. ...
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TypedArray.prototype.findIndex() - JavaScript
st invocation of callback. elements that are appended to the typed array after the call to findindex begins will not be visited by callback. if an existing, unvisited element of the typed array is changed by callback, its value passed to the visiting callback will be the value at the time that findindex visits that element's index; elements that are deleted are not visited. ...
...lements that are appended to the typed array after the call to findindex begins will not be visited by callback. if an existing, unvisited element of the typed array is changed by callback, its value passed to the visiting callback will be the value at the time that findindex visits that element's index; elements that are deleted are not visited. ...
... the typed array after the call to findindex begins will not be visited by callback. if an existing, unvisited element of the typed array is changed by callback, its value passed to the visiting callback will be the value at the time that findindex visits that element's index; elements that are deleted are not visited. ...
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JS_GetPrototype
retrieves an object's prototype. syntax bool js_getprototype(jscontext *cx, js::handleobject obj, js::mutablehandleobject protop); name type description cx jscontext * pointer to a js context from which to derive runtime information. requires request. in a js_threadsafe build, the caller must be in a request on this jscontext. obj js::handleobject object for which to retrieve the prototype. protop js::mutablehandleobject out parameter. if successful, receives prototype object of obj. description js_getprototype retrieves the prototype of a specified object, obj. a prototype object provides properties inherited by similar js objects. this is the equivalent of object.getprototypeof(obj) from javascript. ...
...ct object for which to retrieve the prototype. protop js::mutablehandleobject out parameter. if successful, receives prototype object of obj. description js_getprototype retrieves the prototype of a specified object, obj. a prototype object provides properties inherited by similar js objects. this is the equivalent of object.getprototypeof(obj) from javascript. if js_getprototype returns false, that signals an exception, which should be handled as usual. otherwise, it stores a pointer to the prototype or null to *protop and returns true. to set an object's prototype, use js_setprototype. ...
...object provides properties inherited by similar js objects. this is the equivalent of object.getprototypeof(obj) from javascript. if js_getprototype returns false, that signals an exception, which should be handled as usual. otherwise, it stores a pointer to the prototype or null to *protop and returns true. ...
...roperties inherited by similar js objects. this is the equivalent of object.getprototypeof(obj) from javascript. if js_getprototype returns false, that signals an exception, which should be handled as usual. otherwise, it stores a pointer to the prototype or null to *protop and returns true. to set an object's prototype, use js_setprototype. ...

Object.prototype.valueOf() - JavaScript
expected. by default, the valueof method is inherited by every object descended from object. every built-in core object overrides this method to return an appropriate value. if an object has no primitive value, valueof returns the object itself. you can use valueof within your own code to convert a built-in object into a primitive value. when you create a custom object, you can override object.prototype.valueof() to call a custom method instead of the default object method. overriding valueof for custom objects you can create a function to be called in place of the default valueof method. your function must take no arguments. suppose you have an object type mynumbertype and you want to create a valueof method for it. the following code assigns a user-defined function to the object's valueof m...
...custom method instead of the default object method. overriding valueof for custom objects you can create a function to be called in place of the default valueof method. your function must take no arguments. suppose you have an object type mynumbertype and you want to create a valueof method for it. the following code assigns a user-defined function to the object's valueof method: mynumbertype.prototype.valueof = function() { return customprimitivevalue; }; with the preceding code in place, any time an object of type mynumbertype is used in a context where it is to be represented as a primitive value, javascript automatically calls the function defined in the preceding code. an object's valueof method is usually invoked by javascript, but you can invoke it yourself as follows: mynumbertype.va...
...alueof() note: objects in string contexts convert via the tostring() method, which is different from string objects converting to string primitives using valueof. all objects have a string conversion, if only "[object type]". but many objects do not convert to number, boolean, or function. ...
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Reflect.setPrototypeOf() - JavaScript
the static reflect.setprototypeof() method is the same method as object.setprototypeof(), except for its return type. it sets the prototype (i.e., the internal [[prototype]] property) of a specified object to another object or to null, and returns true if the operation was successful, or false otherwise. the source for this interactive example is stored in a github repository. if you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request. syntax reflect.setprototypeof(target, prototype) parameters target the target object of which to set the prototype. prototype the object's new prototype (an object or null). return value a boolean indicating whether or not the prototype was successfully set. ex...
...ps://github.com/mdn/interactive-examples and send us a pull request. syntax reflect.setprototypeof(target, prototype) parameters target the target object of which to set the prototype. prototype the object's new prototype (an object or null). return value a boolean indicating whether or not the prototype was successfully set. exceptions a typeerror, if target is not an object or if prototype is neither an object nor null. description the reflect.setprototypeof method changes the prototype (i.e. the value of the internal [[prototype]] property) of the specified object. ...
...w prototype (an object or null). return value a boolean indicating whether or not the prototype was successfully set. exceptions a typeerror, if target is not an object or if prototype is neither an object nor null. description the reflect.setprototypeof method changes the prototype (i.e. the value of the internal [[prototype]] property) of the specified object. examples using reflect.setprototypeof() reflect.setprototypeof({}, object.prototype) // true // it can change an object's [[prototype]] to null. reflect.setprototypeof({}, null) // true // returns false if target is not extensible. reflect.setprototypeof(object.freeze({}), null) // false // returns false if it cause a prototype chain cycle. ...
...ing reflect.setprototypeof() reflect.setprototypeof({}, object.prototype) // true // it can change an object's [[prototype]] to null. reflect.setprototypeof({}, null) // true // returns false if target is not extensible. reflect.setprototypeof(object.freeze({}), null) // false // returns false if it cause a prototype chain cycle. let target = {} let proto = object.create(target) reflect.setprototypeof(target, proto) // false specifications specification ecmascript (ecma-262)the definition of 'reflect.setprototypeof' in that specification. ...

RegExp.prototype[@@replace]() - JavaScript
project, please clone https://github.com/mdn/interactive-examples and send us a pull request. syntax regexp[symbol.replace](str, newsubstr|function) parameters str a string that is a target of the replacement. newsubstr (replacement) the string that replaces the substring. ...
...substr (replacement) the string that replaces the substring. a number of special replacement patterns are supported; see the specifying a string as a parameter section in string.prototype.replace() page. function (replacement) a function to be invoked to create the new substring. the arguments supplied to this function are described in the specifying a function as a parameter section in string.prototype.replace() page. return value a new string with some or all matches of a pattern replaced by a replacement. description this method is called internally in string.prototype.replace() if the pattern argument is a regexp object. for example, following two examples return same result. 'abc'.replace(/a/, 'a'); /a/[symbol.replace]('abc', 'a'); this method exists for customizing replace behavio...
...a pattern replaced by a replacement. description this method is called internally in string.prototype.replace() if the pattern argument is a regexp object. for example, following two examples return same result. 'abc'.replace(/a/, 'a'); /a/[symbol.replace]('abc', 'a'); this method exists for customizing replace behavior in regexp subclass. if pattern argument is not a regexp object, string.prototype.replace() doesn't call this method, nor creates a regexp object. examples direct call this method can be used in almost the same way as string.prototype.replace(), except the different this and the different arguments order. var re = /-/g; var str = '2016-01-01'; var newstr = re[symbol.replace](str, '.'); console.log(newstr); // 2016.01.01 using @@replace in subclasses subclasses of regex...
... in subclasses subclasses of regexp can override the [@@replace]() method to modify the default behavior. class myregexp extends regexp { constructor(pattern, flags, count) { super(pattern, flags); this.count = count; } [symbol.replace](str, replacement) { // perform @@replace |count| times. var result = str; for (var i = 0; i < this.count; i++) { result = regexp.prototype[symbol.replace].call(this, result, replacement); } return result; } } var re = new myregexp('\\d', '', 3); var str = '01234567'; var newstr = str.replace(re, '#'); // string.prototype.replace calls re[@@replace]. console.log(newstr); // ###34567 specifications specification ecmascript (ecma-262)the definition of 'regexp.prototype[@@replace]' in that specification. ...

RegExp.prototype[@@split]() - JavaScript
optional integer specifying a limit on the number of splits to be found. the [@@split]() method still splits on every match of this regexp pattern (or, in the syntax above, regexp), until the number of split items match the limit or the string falls short of this pattern. return value an array containing substrings as its elements. ...
... let re = /-/g; let str = '2016-01-02'; let result = re[symbol.split](str); console.log(result); // ["2016", "01", "02"] using @@split in subclasses subclasses of regexp can override the [@@split]() method to modify the default behavior. ...
...it(), except the different this and the different order of arguments. let re = /-/g; let str = '2016-01-02'; let result = re[symbol.split](str); console.log(result); // ["2016", "01", "02"] using @@split in subclasses subclasses of regexp can override the [@@split]() method to modify the default behavior. ...
...2"] using @@split in subclasses subclasses of regexp can override the [@@split]() method to modify the default behavior. class myregexp extends regexp { [symbol.split](str, limit) { let result = regexp.prototype[symbol.split].call(this, str, limit); return result.map(x => "(" + x + ")"); } } let re = new myregexp('-'); let str = '2016-01-02'; let result = str.split(re); // string.prototype.split calls re[@@split]. console.log(result); // ["(2016)", "(01)", "(02)"] specifications specification ecmascript (ecma-262)the definition of 'regexp.prototype[@@split]' in that specification. ...

String.prototype.endsWith() - JavaScript
gth. return value true if the given characters are found at the end of the string; otherwise, false. description this method lets you determine whether or not a string ends with another string. this method is case-sensitive. polyfill this method has been added to the ecmascript 6 specification and may not be available in all javascript implementations yet. ...
... the end of the string; otherwise, false. description this method lets you determine whether or not a string ends with another string. this method is case-sensitive. polyfill this method has been added to the ecmascript 6 specification and may not be available in all javascript implementations yet. ...
...ise, false. description this method lets you determine whether or not a string ends with another string. this method is case-sensitive. polyfill this method has been added to the ecmascript 6 specification and may not be available in all javascript implementations yet. ...
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JS_GetErrorPrototype
this article covers features introduced in spidermonkey 38 return the original value of error.prototype. syntax jsobject * js_geterrorprototype(jscontext *cx); name type description cx jscontext * pointer to a js context whose errors should be reported via your function. other contexts in the same runtime can have their own error reporting functions. ...
...atures introduced in spidermonkey 38 return the original value of error.prototype. syntax jsobject * js_geterrorprototype(jscontext *cx); name type description cx jscontext * pointer to a js context whose errors should be reported via your function. other contexts in the same runtime can have their own error reporting functions. description js_geterrorprototype returns the original value of error.prototype from the global object of the current compartment of cx. ...
...name type description cx jscontext * pointer to a js context whose errors should be reported via your function. ...

Array.prototype[@@unscopables] - JavaScript
ecmascript standard prior to the es2015 version. these properties are excluded from with statement bindings. description the default array properties that are excluded from with bindings are: copywithin() entries() fill() find() findindex() includes() keys() values() see symbol.unscopables for how to set unscopables for your own objects. property attributes of array.prototype[@@unscopables] writable no enumerable no configurable yes examples use in with environments the following code works fine in es5 and below. however, in ecmascript 2015 and later, the array.prototype.keys() method was introduced. that means that inside with environments, "keys" would now be the method and not the v...
... enumerable no configurable yes examples use in with environments the following code works fine in es5 and below. however, in ecmascript 2015 and later, the array.prototype.keys() method was introduced. that means that inside with environments, "keys" would now be the method and not the variable. this is where now the built-in @@unscopables array.prototype[@@unscopables] symbol property comes into play and prevents that some of the array methods are being scoped into the with statement. ...
..., in ecmascript 2015 and later, the array.prototype.keys() method was introduced. that means that inside with environments, "keys" would now be the method and not the variable. this is where now the built-in @@unscopables array.prototype[@@unscopables] symbol property comes into play and prevents that some of the array methods are being scoped into the with statement. var keys = []; with (array.prototype) { keys.push('something'); } object.keys(array.prototype[symbol.unscopables]); // ["copywithin", "entries", "fill", "find", "findindex", // "includes", "keys", "values"] specifications specification ecmascript (ecma-262)the definition of 'array.prototype[@@unscopables]' in that specification. ...

Array.prototype.every() - JavaScript
er implementations of the standard. you can work around this by inserting the following code at the beginning of your scripts, allowing use of every in implementations which do not natively support it. this algorithm is exactly the one specified in ecma-262, 5th edition, assuming object and typeerror have their original values, and that callbackfn.call evaluates to the original value of function.prototype.call. if (!array.prototype.every) { array.prototype.every = function(callbackfn, thisarg) { 'use strict'; var t, k; if (this == null) { throw new typeerror('this is null or not defined'); } // 1. let o be the result of calling toobject passing the this // value as the argument. var o = object(this); // 2. let lenvalue be the result of calling the get...
... toobject passing the this // value as the argument. var o = object(this); // 2. let lenvalue be the result of calling the get internal method // of o with the argument "length". // 3. let len be touint32(lenvalue). var len = o.length >>> 0; // 4. if iscallable(callbackfn) is false, throw a typeerror exception. if (typeof callbackfn !== 'function' && object.prototype.tostring.call(callbackfn) !== '[object function]') { throw new typeerror(); } // 5. if thisarg was supplied, let t be thisarg; else let t be undefined. if (arguments.length > 1) { t = thisarg; } // 6. let k be 0. k = 0; // 7. repeat, while k < len while (k < len) { var kvalue; // a. let pk be tostring(k). // this is implicit for...
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Array.prototype.fill() - JavaScript
tive, it is treated as array.length + start. if end is negative, it is treated as array.length + end. fill is intentionally generic: it does not require that its this value be an array object. fill is a mutator method: it will change the array itself and return it, not a copy of it. if the first parameter is an object, each slot in the array will reference that object. polyfill if (!array.prototype.fill) { object.defineproperty(array.prototype, 'fill', { value: function(value) { // steps 1-2. if (this == null) { throw new typeerror('this is null or not defined'); } var o = object(this); // steps 3-5. var len = o.length >>> 0; // steps 6-7. var start = arguments[1]; var relativestart = start >> 0; // step 8. ...
...ep 11. var finalvalue = relativeend < 0 ? math.max(len + relativeend, 0) : math.min(relativeend, len); // step 12. while (k < finalvalue) { o[k] = value; k++; } // step 13. return o; } }); } if you need to support truly obsolete javascript engines that don't support object.defineproperty, it's best not to polyfill array.prototype methods at all, as you can't make them non-enumerable. examples using fill [1, 2, 3].fill(4) // [4, 4, 4] [1, 2, 3].fill(4, 1) // [1, 4, 4] [1, 2, 3].fill(4, 1, 2) // [1, 4, 3] [1, 2, 3].fill(4, 1, 1) // [1, 2, 3] [1, 2, 3].fill(4, 3, 3) // [1, 2, 3] [1, 2, 3].fill(4, -3, -2) // [4, 2, 3] [1, 2, 3].fill(4, nan, nan) // [1, 2, 3...
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Array.prototype.findIndex() - JavaScript
invocation of callback. callback will not process the elements appended to the array after the call to findindex() begins. if an existing, unvisited element of the array is changed by callback, its value passed to the callback will be the value at the time findindex() visits the element's index. elements that are deleted are still visited. polyfill // https://tc39.github.io/ecma262/#sec-array.prototype.findindex if (!array.prototype.findindex) { object.defineproperty(array.prototype, 'findindex', { value: function(predicate) { // 1. let o be ? toobject(this value). if (this == null) { throw new typeerror('"this" is null or not defined'); } var o = object(this); // 2. let len be ? tolength(? get(o, "length")). var len = o.length >>> 0; //...
... k. var kvalue = o[k]; if (predicate.call(thisarg, kvalue, k, o)) { return k; } // e. increase k by 1. k++; } // 7. return -1. return -1; }, configurable: true, writable: true }); } if you need to support truly obsolete javascript engines that do not support object.defineproperty, it is best not to polyfill array.prototype methods at all, as you cannot make them non-enumerable. examples find the index of a prime number in an array the following example returns the index of the first element in the array that is a prime number, or -1 if there is no prime number. function isprime(num) { for (let i = 2; num > i; i++) { if (num % i == 0) { return false; } } return num > 1; } console.log([4, 6, ...
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Array.prototype.lastIndexOf() - JavaScript
de at the beginning of your scripts, allowing use of lastindexof in implementations which do not natively support it. this algorithm is exactly the one specified in ecma-262, 5th edition, assuming object, typeerror, number, math.floor, math.abs, and math.min have their original values. ...
...ts, allowing use of lastindexof in implementations which do not natively support it. this algorithm is exactly the one specified in ecma-262, 5th edition, assuming object, typeerror, number, math.floor, math.abs, and math.min have their original values. ...
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Array.prototype.push() - JavaScript
d array. do not use this method if the second array (morevegs in the example) is very large because the maximum number of parameters that one function can take is limited in practice. see apply() for more details. let vegetables = ['parsnip', 'potato'] let morevegs = ['celery', 'beetroot'] // merge the second array into the first one // equivalent to vegetables.push('celery', 'beetroot') array.prototype.push.apply(vegetables, morevegs) console.log(vegetables) // ['parsnip', 'potato', 'celery', 'beetroot'] using an object in an array-like fashion as mentioned above, push is intentionally generic, and we can use that to our advantage. array.prototype.push can work on an object just fine, as this example shows. note that we don't create an array to store a collection of objects. instead, we s...
...['parsnip', 'potato', 'celery', 'beetroot'] using an object in an array-like fashion as mentioned above, push is intentionally generic, and we can use that to our advantage. array.prototype.push can work on an object just fine, as this example shows. note that we don't create an array to store a collection of objects. instead, we store the collection on the object itself and use call on array.prototype.push to trick the method into thinking we are dealing with an array—and it just works, thanks to the way javascript allows us to establish the execution context in any way we want. let obj = { length: 0, addelem: function addelem(elem) { // obj.length is automatically incremented // every time an element is added. [].push.call(this, elem) } } // let's add ...
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Array.prototype.slice() - JavaScript
e: 2.2}}, 2] mycar[0].color = red newcar[0].color = red the new color of my honda is purple mycar[0].color = purple newcar[0].color = purple array-like objects slice method can also be called to convert array-like objects/collections to a new array. you just bind the method to the object. the arguments inside a function is an example of an 'array-like object'. ...
... = purple array-like objects slice method can also be called to convert array-like objects/collections to a new array. you just bind the method to the object. the arguments inside a function is an example of an 'array-like object'. function list() { return array.prototype.slice.call(arguments) } let list1 = list(1, 2, 3) // [1, 2, 3] binding can be done with the call() method of function.prototype and it can also be reduced using [].slice.call(arguments) instead of array.prototype.slice.call. ...
... inside a function is an example of an 'array-like object'. function list() { return array.prototype.slice.call(arguments) } let list1 = list(1, 2, 3) // [1, 2, 3] binding can be done with the call() method of function.prototype and it can also be reduced using [].slice.call(arguments) instead of array.prototype.slice.call. anyway, it can be simplified using bind. let unboundslice = array.prototype.slice let slice = function.prototype.call.bind(unboundslice) function list() { return slice(arguments) } let list1 = list(1, 2, 3) // [1, 2, 3] specifications specification ecmascript (ecma-262)the definition of 'array.prototype.slice' in that specification. ...

Date.prototype.toISOString() - JavaScript
ub.com/mdn/interactive-examples and send us a pull request. syntax dateobj.toisostring() return value a string representing the given date in the iso 8601 format according to universal time. polyfill this method was standardized in ecma-262 5th edition. ...
...cording to universal time. polyfill this method was standardized in ecma-262 5th edition. ...
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Date.prototype.toString() - JavaScript
ecified date object. the source for this interactive example is stored in a github repository. if you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request. syntax dateobj.tostring() return value a string representing the given date. description date instances inherit their tostring() method from date.prototype, not object.prototype. date.prototype.tostring() returns a string representation of the date in the format specified in ecma-262 which can be summarised as: week day: 3 letter english week day name, e.g. "sat" space month name: 3 letter english month name, e.g. "sep" space date: 2 digit day in month, e.g. "01" space year: 4 digit year, e.g. "2018" space hour: 2 digit hour of day, e.g. ...
... left bracket, i.e. "(" an implementation dependent string representation of the timezone, which might be an abbreviation or full name (there is no standard for names or abbreviations of timezones), e.g. "line islands time" or "lint" right bracket, i.e. ")" e.g. "sat sep 01 2018 14:53:26 gmt+1400 (lint)" until ecmascript 2018 (edition 9), the format of the string returned by date.prototype.tostring was implementation dependent. therefore it should not be relied upon to be in the specified format. the tostring() method is automatically called when a date is to be represented as a text value, e.g. console.log(new date()), or when a date is used in a string concatenation, such as var today = 'today is ' + new date(). tostring() is a generic method, it does not require that its this ...
...nstance, a typeerror is thrown. examples using tostring() the following assigns the tostring() value of a date object to myvar: var x = new date(); var myvar = x.tostring(); // assigns a string value to myvar in the same format as: // mon sep 08 1998 14:36:22 gmt-0700 (pdt) specifications specification ecmascript (ecma-262)the definition of 'date.prototype.tostring' in that specification. ...

Error.prototype.toString() - JavaScript
the tostring() method returns a string representing the specified error object. syntax e.tostring() return value a string representing the specified error object. description the error object overrides the object.prototype.tostring() method inherited by all objects. ...
... the tostring() method returns a string representing the specified error object. syntax e.tostring() return value a string representing the specified error object. description the error object overrides the object.prototype.tostring() method inherited by all objects. ...
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Intl.Collator.prototype.compare() - JavaScript
the source for this interactive example is stored in a github repository. if you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request. syntax collator.compare(string1, string2) parameters string1 string2 the strings to compare against each other. description the compare getter function returns a number indicating how string1 and string2 compare to each other according to the sort order of this collator object: a negative value if string1 comes before string2; a positive value if string1 comes after string2; 0 if they are considered equal. ...
...ch other according to the sort order of this collator object: a negative value if string1 comes before string2; a positive value if string1 comes after string2; 0 if they are considered equal. examples using compare for array sort use the compare getter function for sorting arrays. note that the function is bound to the collator from which it was obtained, so it can be passed directly to array.prototype.sort(). var a = ['offenbach', 'Österreich', 'odenwald']; var collator = new intl.collator('de-u-co-phonebk'); a.sort(collator.compare); console.log(a.join(', ')); // → "odenwald, Österreich, offenbach" using compare for array search use the compare getter function for finding matching strings in arrays: var a = ['congrès', 'congres', 'assemblée', 'poisson']; var collator = new intl.col...
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Intl.DateTimeFormat.prototype.formatToParts() - JavaScript
syntax datetimeformat.formattoparts(date) parameters date optional the date to format. return value an array of objects containing the formatted date in parts. description the formattoparts() method is useful for custom formatting of date strings. it returns an array of objects containing the locale-specific tokens from which it possible to build custom strings while preserving the locale-specific parts. ...
..., { type: 'minute', value: '00' }, { type: 'literal', value: ':' }, { type: 'second', value: '42' }, { type: 'fractionalsecond', value: '000' }, { type: 'literal', value: ' ' }, { type: 'dayperiod', value: 'am' } ] now the information is available separately and it can be formatted and concatenated again in a customized way. for example by using array.prototype.map(), arrow functions, a switch statement, template literals, and array.prototype.reduce(). var datestring = formatter.formattoparts(date).map(({type, value}) => { switch (type) { case 'dayperiod': return `<b>${value}</b>`; default : return value; } }).reduce((string, part) => string + part); this will make the day period bold, when using the formattoparts() method. console.log(f...
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Intl​.List​Format​.prototype​.formatToParts() - JavaScript
each element of the resulting array has two properties: type and value. ...
... each element of the resulting array has two properties: type and value. ...
... returns an array of objects representing the different components that can be used to format a list of values in a locale-aware fashion. syntax intl.listformat.prototype.formattoparts(list) parameters list an array of values to be formatted according to a locale. return value an array of components which contains the formatted parts from the list. description whereas intl.listformat.prototype.format() returns a string being the formated version of the list (according to the given locale and style options), formattoparts() returns an array of the different components of the formated string. each element of the resulting array has two properties: type and value. the type property may be either "element", which refers to a value from the list, or "literal" which refers to a linguistic c...

Intl.NumberFormat.prototype.format() - JavaScript
the source for this interactive example is stored in a github repository. if you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request. syntax numberformat.format(number) parameters number a number or bigint to format. description the format getter function formats a number into a string according to the locale and formatting options of this numberformat object. ...
...r options = { style: 'currency', currency: 'rub' }; var numberformat = new intl.numberformat('ru-ru', options); console.log(numberformat.format(654321.987)); // → "654 321,99 руб." using format with map use the format getter function for formatting all numbers in an array. note that the function is bound to the numberformat from which it was obtained, so it can be passed directly to array.prototype.map. this is considered a historical artefact, as part of a convention which is no longer followed for new features, but is preserved to maintain compatibility with existing programs. var a = [123456.789, 987654.321, 456789.123]; var numberformat = new intl.numberformat('es-es'); var formatted = a.map(n => numberformat.format(n)); console.log(formatted.join('; ')); // → "123.456,789; 987.654...
...tibility with existing programs. var a = [123456.789, 987654.321, 456789.123]; var numberformat = new intl.numberformat('es-es'); var formatted = a.map(n => numberformat.format(n)); console.log(formatted.join('; ')); // → "123.456,789; 987.654,321; 456.789,123" specifications specification ecmascript internationalization api (ecma-402)the definition of 'intl.numberformat.prototype.format' in that specification. ...

Intl.NumberFormat.prototype.formatToParts() - JavaScript
return value an array of objects containing the formatted number in parts. description the formattoparts() method is useful for custom formatting of number strings. it returns an array of objects containing the locale-specific tokens from which it possible to build custom strings while preserving the locale-specific parts. ...
..."integer", value: "3" }, { type: "group", value: "." }, { type: "integer", value: "500" }, { type: "decimal", value: "," }, { type: "fraction", value: "00" }, { type: "literal", value: " " }, { type: "currency", value: "€" } ] now the information is available separately and it can be formatted and concatenated again in a customized way. for example by using array.prototype.map(), arrow functions, a switch statement, template literals, and array.prototype.reduce(). var numberstring = formatter.formattoparts(number).map(({type, value}) => { switch (type) { case 'currency': return `<strong>${value}</strong>`; default : return value; } }).reduce((string, part) => string + part); this will make the currency bold, when using the formattoparts() method. co...
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Number.prototype.toLocaleString() - JavaScript
); } catch (e) { return e.name === 'rangeerror'; } return false; } prior to es5.1, implementations were not required to throw a range error exception if tolocalestring is called with arguments. a check that works in all hosts, including those supporting ecma-262 prior to ed 5.1, is to test for the features specified in ecma-402 that are required to support regional options for number.prototype.tolocalestring directly: function tolocalestringsupportsoptions() { return !!(typeof intl == 'object' && intl && typeof intl.numberformat == 'function'); } this tests for a global intl object, checks that it's not null and that it has a numberformat property that is a function. using locales this example shows some of the variations in localized number formats. in order to get the format o...
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Promise.prototype.then() - JavaScript
the execution of a function to the moment the stack is empty settimeout(() => { console.log(thenprom); }); // logs, in order: // promise {[[promisestatus]]: "pending", [[promisevalue]]: undefined} // "this gets called after the end of the main stack. the value received and returned is: 33" // promise {[[promisestatus]]: "resolved", [[promisevalue]]: 33} description as the then and promise.prototype.catch() methods return promises, they can be chained — an operation called composition. examples using the then method var p1 = new promise((resolve, reject) => { resolve('success!'); // or // reject(new error("error!")); }); p1.then(value => { console.log(value); // success! }, reason => { console.error(reason); // error! }); chaining the then method returns a promise which al...
... const nexttick = (() => { const noop = () => {}; // literally const nexttickpromise = () => promise.resolve().then(noop); const rfab = reflect.apply.bind; // (thisarg, fn, thisarg, [...args]) const nexttick = (fn, ...args) => ( fn !== undefined ? promise.resolve(args).
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RegExp.prototype[@@match]() - JavaScript
tive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request. syntax regexp[symbol.match](str) parameters str a string that is a target of the match. return value an array containing the entire match result and any parentheses-captured matched results, or null if there were no matches. description this method is called internally in string.prototype.match(). for example, the following two examples return same result. 'abc'.match(/a/); /a/[symbol.match]('abc'); this method exists for customizing match behavior within regexp subclasses. examples direct call this method can be used in almost the same way as string.prototype.match(), except the different this and the different arguments order. let re = /[0-9]+/g; let str = '2016-01-02'; ...
...e.match(), except the different this and the different arguments order. let re = /[0-9]+/g; let str = '2016-01-02'; let result = re[symbol.match](str); console.log(result); // ["2016", "01", "02"] using @@match in subclasses subclasses of regexp can override the [@@match]() method to modify the default behavior. class myregexp extends regexp { [symbol.match](str) { let result = regexp.prototype[symbol.match].call(this, str); if (!result) return null; return { group(n) { return result[n]; } }; } } let re = new myregexp('([0-9]+)-([0-9]+)-([0-9]+)'); let str = '2016-01-02'; let result = str.match(re); // string.prototype.match calls re[@@match]. console.log(result.group(1)); // 2016 console.log(result.group(2)); // 01 console.log(result.group(3)); // 02 ...
...eturn result[n]; } }; } } let re = new myregexp('([0-9]+)-([0-9]+)-([0-9]+)'); let str = '2016-01-02'; let result = str.match(re); // string.prototype.match calls re[@@match]. console.log(result.group(1)); // 2016 console.log(result.group(2)); // 01 console.log(result.group(3)); // 02 specifications specification ecmascript (ecma-262)the definition of 'regexp.prototype[@@match]' in that specification. ...

RegExp.prototype[@@matchAll]() - JavaScript
ce for this interactive example is stored in a github repository. if you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request. syntax regexp[symbol.matchall](str) parameters str a string that is a target of the match. return value an iterator. description this method is called internally in string.prototype.matchall(). for example, the following two examples return same result. 'abc'.matchall(/a/); /a/[symbol.matchall]('abc'); this method exists for customizing the behavior of matchall() in regexp subclasses. examples direct call this method can be used in almost the same way as string.prototype.matchall(), except for the different value of this and the different order of arguments. let re = ...
...et str = '2016-01-02'; let result = re[symbol.matchall](str); console.log(array.from(result, x => x[0])); // ["2016", "01", "02"] using @@matchall in subclasses subclasses of regexp can override the [@@matchall]() method to modify the default behavior. ...
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RegExp.prototype.flags - JavaScript
the flags property returns a string consisting of the flags of the current regular expression object. the source for this interactive example is stored in a github repository. if you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request. ...
... please clone https://github.com/mdn/interactive-examples and send us a pull request. property attributes of regexp.prototype.flags writable no enumerable no configurable yes description flags in the flags property are sorted alphabetically (from left to right, e.g. "gimsuy"). ...
...nd us a pull request. property attributes of regexp.prototype.flags writable no enumerable no configurable yes description flags in the flags property are sorted alphabetically (from left to right, e.g. "gimsuy"). polyfill if (regexp.prototype.flags === undefined) { object.defineproperty(regexp.prototype, 'flags', { configurable: true, get: function() { return this.tostring().match(/[gimsuy]*$/)[0]; } }); } examples using flags /foo/ig.flags; // "gi" /bar/myu.flags; // "muy" specifications specification ecmascript (ecma-262)the definition of 'regexp.prototype.flags' in that specification. ...

String.prototype.codePointAt() - JavaScript
returns undefined. description if there is no element at the specified position, undefined is returned. if no utf-16 surrogate pair begins at pos, the code unit at pos is returned. polyfill the following extends strings to include the codepointat() function as specified in ecmascript 2015 for browsers without native support. ...
... is a next code unit ) { second = string.charcodeat(index + 1); if (second >= 0xdc00 && second <= 0xdfff) { // low surrogate // https://mathiasbynens.be/notes/javascript-encoding#surrogate-formulae return (first - 0xd800) * 0x400 + second - 0xdc00 + 0x10000; } } return first; }; if (defineproperty) { defineproperty(string.prototype, 'codepointat', { 'value': codepointat, 'configurable': true, 'writable': true }); } else { string.prototype.codepointat = codepointat; } }()); } examples using codepointat() 'abc'.codepointat(1) // 66 '\ud800\udc00'.codepointat(0) // 65536 'xyz'.codepointat(42) // undefined looping with codepointat() for (let codepoint of ...
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String.prototype.includes() - JavaScript
not a string includes another string. case-sensitivity the includes() method is case sensitive. for example, the following expression returns false: 'blue whale'.includes('blue') // returns false polyfill this method has been added to the ecmascript 2015 specification and may not be available in all javascript implementations yet. ...
...tring. case-sensitivity the includes() method is case sensitive. for example, the following expression returns false: 'blue whale'.includes('blue') // returns false polyfill this method has been added to the ecmascript 2015 specification and may not be available in all javascript implementations yet. ...
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String.prototype.match() - JavaScript
lar expression does not include the g flag, str.match() will return the same result as regexp.exec(). other methods if you need to know if a string matches a regular expression regexp, use regexp.test(). if you only want the first match found, you might want to use regexp.exec() instead. if you want to obtain capture groups and the global flag is set, you need to use regexp.exec() or string.prototype.matchall() instead. examples using match() in the following example, match() is used to find 'chapter' followed by 1 or more numeric characters followed by a decimal point and numeric character 0 or more times. the regular expression includes the i flag so that upper/lower case differences will be ignored. const str = 'for more information, see chapter 3.4.5.1'; const re = /see (chapter \d+...
...nstrates the use of the global and ignore case flags with match(). all letters a through e and a through e are returned, each its own element in the array. const str = 'abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz'; const regexp = /[a-e]/gi; const matches_array = str.match(regexp); console.log(matches_array); // ['a', 'b', 'c', 'd', 'e', 'a', 'b', 'c', 'd', 'e'] note: see also string.prototype.matchall() and advanced searching with flags. using named capturing groups in browsers which support named capturing groups, the following code captures "fox" or "cat" into a group named "animal": const paragraph = 'the quick brown fox jumps over the lazy dog. it barked.'; const capturingregex = /(?<animal>fox|cat) jumps over/; const found = paragraph.match(capturingregex); console.log(found...
...nfinity is the number. returns ["infinity"] str1.match(+infinity); // returns ["infinity"] str1.match(-infinity); // returns ["-infinity"] str2.match(65); // returns ["65"] str2.match(+65); // a number with a positive sign. returns ["65"] str3.match(null); // returns ["null"] specifications specification ecmascript (ecma-262)the definition of 'string.prototype.match' in that specification. ...

String.prototype.repeat() - JavaScript
new string containing the specified number of copies of the given string. exceptions rangeerror: repeat count must be non-negative. rangeerror: repeat count must be less than infinity and not overflow maximum string size. polyfill this method has been added to the ecmascript 2015 specification and may not be available in all javascript implementations yet. however, you can polyfill string.prototype.repeat() with the following snippet: if (!string.prototype.repeat) { string.prototype.repeat = function(count) { 'use strict'; if (this == null) throw new typeerror('can\'t convert ' + this + ' to object'); var str = '' + this; // to convert string to integer. count = +count; // check nan if (count != count) count = 0; if (count < 0) throw ne...
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String.prototype.startsWith() - JavaScript
urn value true if the given characters are found at the beginning of the string; otherwise, false. description this method lets you determine whether or not a string begins with another string. this method is case-sensitive. polyfill this method has been added to the ecmascript 2015 specification and may not be available in all javascript implementations yet. ...
...ng of the string; otherwise, false. description this method lets you determine whether or not a string begins with another string. this method is case-sensitive. polyfill this method has been added to the ecmascript 2015 specification and may not be available in all javascript implementations yet. however, you can polyfill string.prototype.startswith() with the following snippet: if (!string.prototype.startswith) { object.defineproperty(string.prototype, 'startswith', { value: function(search, rawpos) { var pos = rawpos > 0 ? rawpos|0 : 0; return this.substring(pos, pos + search.length) === search; } }); } a more robust (fully es2015 specification compliant), but less performant and compact, polyfill is available on github by mathias bynens. ...
...able on github by mathias bynens. examples using startswith() //startswith let str = 'to be, or not to be, that is the question.' console.log(str.startswith('to be')) // true console.log(str.startswith('not to be')) // false console.log(str.startswith('not to be', 10)) // true specifications specification ecmascript (ecma-262)the definition of 'string.prototype.startswith' in that specification. ...

String.prototype.substr() - JavaScript
s not support negative values for the start index. ...
...{string} */ string.prototype.substr = function(substr) { return function(start, length) { // call the original method return substr.call(this, // did we get a negative start, calculate how much it is from the beginning of the string // adjust the start parameter for negative value start < 0 ? ...
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String.prototype.trimEnd() - JavaScript
s a pull request. syntax str.trimend(); str.trimright(); return value a new string representing the calling string stripped of whitespace from its (right) end. description the trimend() / trimright() methods return the string stripped of whitespace from its right end. trimend() or trimright() do not affect the value of the string itself. ...
...tion the trimend() / trimright() methods return the string stripped of whitespace from its right end. trimend() or trimright() do not affect the value of the string itself. aliasing for consistency with functions like string.prototype.padend the standard method name is trimend. however, for web compatibility reasons, trimright remains as an alias to trimend. ...
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TypedArray.prototype.copyWithin() - JavaScript
typedarray is one of the typed array types here. the source for this interactive example is stored in a github repository. ...
...s and send us a pull request. syntax typedarray.copywithin(target, start[, end = this.length]) parameters target target start index position where to copy the elements to. start source start index position where to start copying elements from. end optional optional. source end index position where to end copying elements from. return value the modified array. description see array.prototype.copywithin for more details. examples using copywithin var buffer = new arraybuffer(8); var uint8 = new uint8array(buffer); uint8.set([1,2,3]); console.log(uint8); // uint8array [ 1, 2, 3, 0, 0, 0, 0, 0 ] uint8.copywithin(3,0,3); console.log(uint8); // uint8array [ 1, 2, 3, 1, 2, 3, 0, 0 ] specifications specification ecmascript (ecma-262)the definition of 'typedarray.
....copywithin for more details. examples using copywithin var buffer = new arraybuffer(8); var uint8 = new uint8array(buffer); uint8.set([1,2,3]); console.log(uint8); // uint8array [ 1, 2, 3, 0, 0, 0, 0, 0 ] uint8.copywithin(3,0,3); console.log(uint8); // uint8array [ 1, 2, 3, 1, 2, 3, 0, 0 ] specifications specification ecmascript (ecma-262)the definition of 'typedarray.prototype.copywithin' in that specification. ...

TypedArray.prototype.join() - JavaScript
typedarray is one of the typed array types here. the source for this interactive example is stored in a github repository. if you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request. syntax typedarray.join([separator = ',']); parameters separator optional. specifies a string to separate each element. the separator is converted to a string if necessary. if omitted, the typed array elements are separated with a comma (","). ...
... specifies a string to separate each element. the separator is converted to a string if necessary. if omitted, the typed array elements are separated with a comma (","). return value a string with all array elements joined. polyfill since there is no global object with the name typedarray, polyfilling must be done on an "as needed" basis. // https://tc39.github.io/ecma262/#sec-%typedarray%.prototype.join if (!uint8array.prototype.join) { object.defineproperty(uint8array.prototype, 'join', { value: array.prototype.join }); } if you need to support truly obsolete javascript engines that don't support object.defineproperty, it's best not to polyfill array.prototype methods at all, as you can't make them non-enumerable. examples using join var uint8 = new uint8array([1,2,3]); uint8...
...ngines that don't support object.defineproperty, it's best not to polyfill array.prototype methods at all, as you can't make them non-enumerable. examples using join var uint8 = new uint8array([1,2,3]); uint8.join(); // '1,2,3' uint8.join(' / '); // '1 / 2 / 3' uint8.join(''); // '123' specifications specification ecmascript (ecma-262)the definition of 'typedarray.prototype.join' in that specification. ...

TypedArray.prototype.reduce() - JavaScript
typedarray is one of the typed array types here. the source for this interactive example is stored in a github repository. if you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request. ...
...value will be equal to the second. if the typed array is empty and no initialvalue was provided, typeerror would be thrown. if the typed array has only one element (regardless of position) and no initialvalue was provided, or if initialvalue is provided but the typed array is empty, the solo value would be returned without calling callback. ...
...lue was provided, typeerror would be thrown. if the typed array has only one element (regardless of position) and no initialvalue was provided, or if initialvalue is provided but the typed array is empty, the solo value would be returned without calling callback. polyfill this method uses the same algorithm as array.prototype.reduce(), so the same polyfill can be used here: simply replace array.prototype.reduce with typedarray.prototype.reduce. examples sum up all values within an array var total = new uint8array([0, 1, 2, 3]).reduce(function(a, b) { return a + b; }); // total == 6 specifications specification ecmascript (ecma-262)the definition of '%typedarray%.prototype.reduce' in that specification. ...

TypedArray.prototype.slice() - JavaScript
typedarray is one of the typed array types here. the source for this interactive example is stored in a github repository. if you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request. syntax typedarray.slice([begin[, end]]) parameters begin optional zero-based index at which to begin extraction. a negative index can be used, indicating an offset from the end of the sequence. ...
...alue a new typed array containing the extracted elements. description the slice method does not alter. it returns a shallow copy of elements from the original typed array. if a new element is added to either typed array, the other typed array is not affected. polyfill since there is no global object with the name typedarray, polyfilling must be done on an "as needed" basis. if (!uint8array.prototype.slice) { object.defineproperty(uint8array.prototype, 'slice', { value: function (begin, end) { return new uint8array(array.prototype.slice.call(this, begin, end)); } }); } if you need to support truly obsolete javascript engines that don't support object.defineproperty, it's best not to polyfill array.prototype methods at all, as you can't make them non-enumerable. e...
...l, as you can't make them non-enumerable. examples return a portion of an existing typed array const uint8 = new uint8array([1,2,3]); uint8.slice(1); // uint8array [ 2, 3 ] uint8.slice(2); // uint8array [ 3 ] uint8.slice(-2); // uint8array [ 2, 3 ] uint8.slice(0,1); // uint8array [ 1 ] specifications specification ecmascript (ecma-262)the definition of '%typedarray%.prototype.slice' in that specification. ...

TypedArray.prototype.some() - JavaScript
typedarray is one of the typed array types here. the source for this interactive example is stored in a github repository. if you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request. ...
...d for use as its this value. the this value ultimately observable by callback is determined according to the usual rules for determining the this seen by a function. some does not mutate the typed array on which it is called. polyfill since there is no global object with the name typedarray, polyfilling must be done on an "as needed" basis. // https://tc39.github.io/ecma262/#sec-%typedarray%.prototype.some if (!uint8array.prototype.some) { object.defineproperty(uint8array.prototype, 'some', { value: array.prototype.some }); } if you need to support truly obsolete javascript engines that don't support object.defineproperty, it's best not to polyfill array.prototype methods at all, as you can't make them non-enumerable. examples testing size of all typed array elements the followin...
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TypedArray.prototype.toLocaleString() - JavaScript
typedarray is one of the typed array types here. ...
...typedarray is one of the typed array types here. ...
... ...

WebAssembly.Table.prototype.set() - JavaScript
if value is not an exported webassembly function or null, a typeerror is thrown. examples using table.set the following example (see table2.html source code and live version) creates a new webassembly table instance with an initial size of 2 references. ...
...ence stored at a given index to a different value. syntax table.set(index, value); parameters index the index of the function reference you want to mutate. value the value you want to mutate the reference to. this must be an exported webassembly function, a javascript wrapper for an underlying wasm function. return value void. ...
...l to table.prototype.length, a rangeerror is thrown. if value is not an exported webassembly function or null, a typeerror is thrown. examples using table.set the following example (see table2.html source code and live version) creates a new webassembly table instance with an initial size of 2 references. we then print out the table length and contents of the two indexes (retrieved via table.prototype.get()) to show that the length is two, and the indexes currently contain no function references (they currently return null). var tbl = new webassembly.table({initial:2, element:"anyfunc"}); console.log(tbl.length); console.log(tbl.get(0)); console.log(tbl.get(1)); we then create an import object that contains a reference to the table: var importobj = { js: { tbl:tbl } }; finally, we ...

Date.prototype.toLocaleFormat() - Archive of obsolete content
the non-standard tolocaleformat() method converts a date to a string using the specified formatting. intl.datetimeformat is an alternative to format dates in a standards-compliant way. see also the newer version of date.prototype.tolocaledatestring(). this feature has been removed and will no longer work in firefox 58+. see warning: date.prototype.tolocaleformat is deprecated for more information and migration help. syntax dateobj.tolocaleformat(formatstring) parameters formatstring a format string in the same format expected by the strftime() function in c. return value a string representing the given date using the specified formatting. description the tolocaleformat() method provides greater software control over the formatting of the generated date and/or time. names for...
...g this method. examples using tolocaleformat() var today = new date(); var date = today.tolocaleformat('%a, %b %e, %y'); in this example, tolocaleformat() returns a string such as "wednesday, october 3, 2007". note that the format string in this example is not properly localized, which will result in the problems described above. polyfill when using the datejs library you can polyfill date.prototype.tolocaledatestring() like this: if (!date.prototype.tolocaleformat) { (function() { date.prototype.tolocaleformat = function(formatstring) { return this.format(formatstring); }; }()); } specifications not part of any standard. ...

Prototype-based programming - MDN Web Docs Glossary: Definitions of Web-related terms
prototype-based programming is a style of object-oriented programming in which classes are not explicitly defined, but rather derived by adding properties and methods to an instance of another class or, less frequently, adding them to an empty object. in simple words: this type of style allows the creation of an object without first defining its class. ...
... prototype-based programming is a style of object-oriented programming in which classes are not explicitly defined, but rather derived by adding properties and methods to an instance of another class or, less frequently, adding them to an empty object. in simple words: this type of style allows the creation of an object without first defining its class. ...

Prototype - MDN Web Docs Glossary: Definitions of Web-related terms
a prototype is a model that displays the appearance and behavior of an application or product early in the development lifecycle. ...
... a prototype is a model that displays the appearance and behavior of an application or product early in the development lifecycle. ...

JS_GetArrayPrototype
this article covers features introduced in spidermonkey 24 retrieves the original, canonical array.prototype for an object's global object. syntax jsobject * js_getarrayprototype(jscontext *cx, js::handleobject forobj); name type description cx jscontext * pointer to a javascript context from which to derive runtime information. requires request. in a js_threadsafe build, the caller must be in a request on this jscontext. forobj js::handleobject an object from the global whose array.prototype is being retrieved. description js_getarrayprototype() retrieves the original array.prototype of a specified object, obj. if an error occurs, it returns null. note: this expression might have different values over time if the global array property...
...ect from the global whose array.prototype is being retrieved. description js_getarrayprototype() retrieves the original array.prototype of a specified object, obj. if an error occurs, it returns null. note: this expression might have different values over time if the global array property is modified, but this method returns only the original value. ...

JS_GetClassPrototype
get the builtin class prototype object. syntax bool js_getclassprototype(jscontext *cx, jsprotokey key, js::mutablehandle<jsobject*> objp); name type description cx jscontext * a context. requires request. in a js_threadsafe build, the caller must be in a request on this jscontext. key jsprotokey the key of the prototype. objp js::mutablehandle&lt;jsobject*&gt; out parameter. if successful, receive the class prototype object. description js_getclassprototype gets the builtin class costructor for the specified prototype key. if successful, js_getclassprototype stores the class prototype object to *objp and returns true, otherwise returns false and the value of *objp is undefined. see also mxr id sear...
...ndle&lt;jsobject*&gt; out parameter. if successful, receive the class prototype object. description js_getclassprototype gets the builtin class costructor for the specified prototype key. if successful, js_getclassprototype stores the class prototype object to *objp and returns true, otherwise returns false and the value of *objp is undefined. ...

JS_GetFunctionPrototype
this article covers features introduced in spidermonkey 17 retrieves the original, canonical function.prototype for an object's global object. syntax jsobject * js_getfunctionprototype(jscontext *cx, js::handleobject forobj); name type description cx jscontext * pointer to a javascript context from which to derive runtime information. requires request. in a js_threadsafe build, the caller must be in a request on this jscontext. forobj js::handleobject an object from the global whose function.prototype is being retrieved. description js_getfunctionprototype() retrieves the original function.prototype of a specified object, obj. if an error occurs, it returns null. note: this expression might have different values over time if...
...bal whose function.prototype is being retrieved. description js_getfunctionprototype() retrieves the original function.prototype of a specified object, obj. if an error occurs, it returns null. note: this expression might have different values over time if the global function property is modified, but this method returns only the original value. ...

JS_GetObjectPrototype
this article covers features introduced in spidermonkey 17 retrieves the original, canonical object.prototype for an object's global object. syntax jsobject * js_getobjectprototype(jscontext *cx, js::handleobject forobj); name type description cx jscontext * pointer to a javascript context from which to derive runtime information. requires request. in a js_threadsafe build, the caller must be in a request on this jscontext. forobj js::handleobject an object from the global whose object.prototype is being retrieved. description js_getobjectprototype() retrieves the original object.prototype of a specified object, obj. if an error occurs, it returns null. note: this expression might have different values over time if the global object pr...
...rom the global whose object.prototype is being retrieved. description js_getobjectprototype() retrieves the original object.prototype of a specified object, obj. if an error occurs, it returns null. note: this expression might have different values over time if the global object property is modified, but this method returns only the original value. ...

NodeList.prototype.forEach() - Web APIs
unction(currentvalue, currentindex, listobj) { console.log(currentvalue + ', ' + currentindex + ', ' + this); }, 'mythisarg' ); the above code results in the following: [object htmlparagraphelement], 0, mythisarg [object text], 1, mythisarg [object htmlspanelement], 2, mythisarg polyfill this polyfill adds compatibility to all browsers supporting es5: if (window.nodelist && !nodelist.prototype.foreach) { nodelist.prototype.foreach = function (callback, thisarg) { thisarg = thisarg || window; for (var i = 0; i < this.length; i++) { callback.call(thisarg, this[i], i, this); } }; } or if (window.nodelist && !nodelist.prototype.foreach) { nodelist.prototype.foreach = array.prototype.foreach; } the above behavior is how many browsers actuall...
... specifications specification status comment web idlthe definition of 'foreach' in that specification. candidate recommendation defines foreach on iterable declarations browser compatibility the compatibility table on this page is generated from structured data. ...

TextEncoder.prototype.encode() - Web APIs
syntax b1 = encoder.encode(string); parameters string is a usvstring containing the text to encode. return value a uint8array object. ...
... living standard initial definition. ...

Warning: Date.prototype.toLocaleFormat is deprecated - JavaScript
the javascript warning "date.prototype.tolocaleformat is deprecated; consider using intl.datetimeformat instead" occurs when the non-standard date.prototype.tolocaleformat method is used. message warning: date.prototype.tolocaleformat is deprecated; consider using intl.datetimeformat instead error type warning. javascript execution won't be halted. what went wrong? the non-standard date.prototype.tolocaleformat method is deprecated and shouldn't be used anymore. it uses a format string in the same format expected by the strftime() function in c. the function is no longer available in firefox 58+. examples deprecated syntax the date.prototype.tolocaleformat method is deprecated and will be removed (no cross-browser support, available in firefox only). var today = new date(); var date = t...
...= today.tolocaleformat('%a, %e. %b %y'); console.log(date); // in german locale // "freitag, 10. märz 2017" alternative standard syntax using the ecmascript intl api the ecma-402 (ecmascript intl api) standard specifies standard objects and methods that enable language sensitive date and time formatting (available in chrome 24+, firefox 29+, ie11+, safari10+). you can now either use the date.prototype.tolocaledatestring method if you just want to format one date. var today = new date(); var options = { weekday: 'long', year: 'numeric', month: 'long', day: 'numeric' }; var date = today.tolocaledatestring('de-de', options); console.log(date); // "freitag, 10. märz 2017" or, you can make use of the intl.datetimeformat object, which allows you to cache an object with most of t...

Array.prototype[@@iterator]() - JavaScript
+ "</li>"; } result alternative iteration var arr = ['a', 'b', 'c', 'd', 'e']; var earr = arr[symbol.iterator](); console.log(earr.next().value); // a console.log(earr.next().value); // b console.log(earr.next().value); // c console.log(earr.next().value); // d console.log(earr.next().value); // e use case for brace notation the use case for this syntax over using the dot notation (array.prototype.values()) is in a case where you don't know what object is going to be ahead of time. if you have a function that takes an iterator and then iterate over the value, but don't know if that object is going to have a [iterable].prototype.values method. this could be a built-in object like string object or a custom object. function logiterable(it) { if (!(symbol.iterator in object.getprototypeof(it...
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Array.prototype.copyWithin() - JavaScript
asted as one operation; pasted sequence will have the copied values even when the copy and paste region overlap. the copywithin function is intentionally generic, it does not require that its this value be an array object. the copywithin method is a mutable method. it does not alter the length of this, but it will change its content and create new properties, if necessary. polyfill if (!array.prototype.copywithin) { object.defineproperty(array.prototype, 'copywithin', { value: function(target, start/*, end*/) { // steps 1-2. if (this == null) { throw new typeerror('this is null or not defined'); } var o = object(this); // steps 3-5. var len = o.length >>> 0; // steps 6-8. var relativetarget = target >> 0; var to = relativetarget < 0 ? ma...
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Array.prototype.flatMap() - JavaScript
tvalue the current element being processed in the array. indexoptional the index of the current element being processed in the array. arrayoptional the array map was called upon. thisargoptional value to use as this when executing callback. return value a new array with each element being the result of the callback function and flattened to a depth of 1. description see array.prototype.map() for a detailed description of the callback function. the flatmap method is identical to a map followed by a call to flat of depth 1. alternative reduce() and concat() var arr = [1, 2, 3, 4]; arr.flatmap(x => [x, x * 2]); // is equivalent to arr.reduce((acc, x) => acc.concat([x, x * 2]), []); // [1, 2, 2, 4, 3, 6, 4, 8] note, however, that this is inefficient and should be avoided for ...
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Array.prototype.includes() - JavaScript
.includes('c', -100) // true arr.includes('a', -2) // false includes() used as a generic method includes() method is intentionally generic. it does not require this value to be an array object, so it can be applied to other kinds of objects (e.g. array-like objects). the example below illustrates includes() method called on the function's arguments object. (function() { console.log(array.prototype.includes.call(arguments, 'a')) // true console.log(array.prototype.includes.call(arguments, 'd')) // false })('a','b','c') please do not add polyfills on reference articles. for more details and discussion, see https://discourse.mozilla.org/t/mdn-rfc-001-mdn-wiki-pages-shouldnt-be-a-distributor-of-polyfills/24500 specifications specification ecmascript (ecma-262)th...
...s, 'a')) // true console.log(array.prototype.includes.call(arguments, 'd')) // false })('a','b','c') please do not add polyfills on reference articles. for more details and discussion, see https://discourse.mozilla.org/t/mdn-rfc-001-mdn-wiki-pages-shouldnt-be-a-distributor-of-polyfills/24500 specifications specification ecmascript (ecma-262)the definition of 'array.prototype.includes' in that specification. ...

Array.prototype.pop() - JavaScript
e last element from an array and returns that value to the caller. pop is intentionally generic; this method can be called or applied to objects resembling arrays. objects which do not contain a length property reflecting the last in a series of consecutive, zero-based numerical properties may not behave in any meaningful manner. if you call pop() on an empty array, it returns undefined. array.prototype.shift() has similar behavior to pop, but applied to the first element in an array. examples removing the last element of an array the following code creates the myfish array containing four elements, then removes its last element. var myfish = ['angel', 'clown', 'mandarin', 'sturgeon']; var popped = myfish.pop(); console.log(myfish); // ['angel', 'clown', 'mandarin' ] console.log(popped); ...
...myfish); // ['angel', 'clown', 'mandarin' ] console.log(popped); // 'sturgeon' using apply( ) or call ( ) on array-like objects the following code creates the myfish array-like object containing four elements and a length parameter, then removes its last element and decrements the length parameter. var myfish = {0:'angel', 1:'clown', 2:'mandarin', 3:'sturgeon', length: 4}; var popped = array.prototype.pop.call(myfish); //same syntax for using apply( ) console.log(myfish); // {0:'angel', 1:'clown', 2:'mandarin', length: 3} console.log(popped); // 'sturgeon' specifications specification ecmascript (ecma-262)the definition of 'array.prototype.pop' in that specification. ...

Array.prototype.shift() - JavaScript
the values at consecutive indexes down, then returns the removed value. if the length property is 0, undefined is returned. shift is intentionally generic; this method can be called or applied to objects resembling arrays. objects which do not contain a length property reflecting the last in a series of consecutive, zero-based numerical properties may not behave in any meaningful manner. array.prototype.pop() has similar behavior to shift, but applied to the last element in an array. examples removing an element from an array the following code displays the myfish array before and after removing its first element. it also displays the removed element: var myfish = ['angel', 'clown', 'mandarin', 'surgeon']; console.log('myfish before:', json.stringify(myfish)); // myfish before: ['angel', 'c...
...ed in condition inside while loop. in the following example every iteration will remove the next element from an array, until it is empty: var names = ["andrew", "edward", "paul", "chris" ,"john"]; while( (i = names.shift()) !== undefined ) { console.log(i); } // andrew, edward, paul, chris, john specifications specification ecmascript (ecma-262)the definition of 'array.prototype.shift' in that specification. ...

BigInt.prototype.toLocaleString() - JavaScript
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BigInt.prototype.toString() - JavaScript
tional. an integer in the range 2 through 36 specifying the base to use for representing numeric values. return value a string representing the specified bigint object. exceptions rangeerror if tostring() is given a radix less than 2 or greater than 36, a rangeerror is thrown. description the bigint object overrides the tostring() method of the object object; it does not inherit object.prototype.tostring(). for bigint objects, the tostring() method returns a string representation of the object in the specified radix. the tostring() method parses its first argument, and attempts to return a string representation in the specified radix (base). for radixes above 10, the letters of the alphabet indicate numerals greater than 9. for example, for hexadecimal numbers (base 16) a through f are ...
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Boolean.prototype.toString() - JavaScript
ive example is stored in a github repository. if you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request. syntax bool.tostring() return value a string representing the specified boolean object. description the boolean object overrides the tostring method of the object object; it does not inherit object.prototype.tostring(). for boolean objects, the tostring method returns a string representation of the object. javascript calls the tostring() method automatically when a boolean is to be represented as a text value or when a boolean is referred to in a string concatenation. for boolean objects and values, the built-in tostring() method returns the string "true" or "false" depending on the value of the bo...
...atenation. for boolean objects and values, the built-in tostring() method returns the string "true" or "false" depending on the value of the boolean object. examples using tostring() in the following code, flag.tostring() returns "true": var flag = new boolean(true); var myvar = flag.tostring(); specifications specification ecmascript (ecma-262)the definition of 'boolean.prototype.tostring' in that specification. ...

Date.prototype.getDay() - JavaScript
the source for this interactive example is stored in a github repository. if you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request. syntax dateobj.getday() return value an integer number, between 0 and 6, corresponding to the day of the week for the given date, according to local time: 0 for sunday, 1 for monday, 2 for tuesday, and so on. ...
....datetimeformat with an options parameter. using this method, the internationalization is made easier: var options = { weekday: 'long'}; console.log(new intl.datetimeformat('en-us', options).format(xmas95)); // monday console.log(new intl.datetimeformat('de-de', options).format(xmas95)); // montag specifications specification ecmascript (ecma-262)the definition of 'date.prototype.getday' in that specification. ...

Date.prototype.toLocaleString() - JavaScript
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...9-01-01t01:00:00z").tolocalestring("en-us"); // true in firefox and others // false in ie and edge note: see also this stackoverflow thread for more details and examples. specifications specification ecmascript (ecma-262)the definition of 'date.prototype.tolocalestring' in that specification. ecmascript internationalization api (ecma-402)the definition of 'date.prototype.tolocalestring' in that specification. ...

Date.prototype.toLocaleTimeString() - JavaScript
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Intl.Collator.prototype.resolvedOptions() - JavaScript
the source for this interactive example is stored in a github repository. if you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request. syntax collator.resolvedoptions() return value a new object with properties reflecting the locale and collation options computed during the initialization of the given collator object. description the resulting object has the following properties: locale the bcp 47 language tag for the locale actually used. ...
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Intl.DateTimeFormat.prototype.format() - JavaScript
the source for this interactive example is stored in a github repository. if you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request. syntax datetimeformat.format(date) parameters date the date to format. description the format getter formats a date into a string according to the locale and formatting options of this intl.datetimeformat object. ...
...'long', day: 'numeric' }; var datetimeformat = new intl.datetimeformat('sr-rs', options); console.log(datetimeformat.format(new date())); // → "недеља, 7. април 2013." using format with map use the format getter function for formatting all dates in an array. note that the function is bound to the intl.datetimeformat from which it was obtained, so it can be passed directly to array.prototype.map(). var a = [new date(2012, 08), new date(2012, 11), new date(2012, 03)]; var options = { year: 'numeric', month: 'long' }; var datetimeformat = new intl.datetimeformat('pt-br', options); var formatted = a.map(datetimeformat.format); console.log(formatted.join('; ')); // → "setembro de 2012; dezembro de 2012; abril de 2012" avoid comparing formatted date values to static values most of t...

Intl.DateTimeFormat.prototype.resolvedOptions() - JavaScript
the source for this interactive example is stored in a github repository. if you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request. syntax datetimeformat.resolvedoptions() return value a new object with properties reflecting the locale and date and time formatting options computed during the initialization of the given datetimeformat object. ...
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Intl.NumberFormat.prototype.resolvedOptions() - JavaScript
the source for this interactive example is stored in a github repository. if you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request. syntax numberformat.resolvedoptions() return value a new object with properties reflecting the locale and number formatting options computed during the initialization of the given numberformat object. description the resulting object has the following properties: locale the bcp 47 language tag for the locale actually used. ...
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Intl.PluralRules.prototype.resolvedOptions() - JavaScript
syntax pluralrule.resolvedoptions() return value a new object with properties reflecting the locale and plural formatting options computed during the initialization of the given pluralrules object. description the resulting object has the following properties: locale the bcp 47 language tag for the locale actually used. if any unicode extension values were requested in the input bcp 47 language tag that led to this locale, the key-value pairs that were requested and are supported for this locale are included in locale. ...
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Intl.RelativeTimeFormat.prototype.formatToParts() - JavaScript
the source for this interactive example is stored in a github repository. if you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request. syntax relativetimeformat.formattoparts(value, unit) parameters value numeric value to use in the internationalized relative time message. unit unit to use in the relative time internationalized message. possible values are: "year", "quarter", "month", "week", "day", "hour", "minute", "second". plural forms are also permitted. ...
... value numeric value to use in the internationalized relative time message. unit unit to use in the relative time internationalized message. possible values are: "year", "quarter", "month", "week", "day", "hour", "minute", "second". plural forms are also permitted. return value an array of objects containing the formatted relative time in parts. description the intl.relativetimeformat.prototype.formattoparts method is a version of the format method which it returns an array of objects which represent "parts" of the object, separating the formatted number into its consituent parts and separating it from other surrounding text. these objects have two properties: type a numberformat formattoparts type, and value, which is the string which is the component of the output. if a "part" came fr...

Number.prototype.toFixed() - JavaScript
not a number. description tofixed() returns a string representation of numobj that does not use exponential notation and has exactly digits digits after the decimal place. the number is rounded if necessary, and the fractional part is padded with zeros if necessary so that it has the specified length. if the absolute value of numobj is greater or equal to 1e+21, this method simply calls number.prototype.tostring() and returns a string in exponential notation. warning: floating point numbers cannot represent all decimals precisely in binary. this can lead to unexpected results, such as 0.1 + 0.2 === 0.3 returning false . examples using tofixed let numobj = 12345.6789 numobj.tofixed() // returns '12346': note rounding, no fractional part numobj.tofixed(1) // returns '12345.7': no...
...3' 2.35.tofixed(1) // returns '2.4'. note it rounds up 2.55.tofixed(1) // returns '2.5'. note it rounds down - see warning above -2.34.tofixed(1) // returns -2.3 (due to operator precedence, negative number literals don't return a string...) (-2.34).tofixed(1) // returns '-2.3' specifications specification ecmascript (ecma-262)the definition of 'number.prototype.tofixed' in that specification. ...

Number.prototype.toPrecision() - JavaScript
a string representing the number object to the specified precision. syntax numobj.toprecision([precision]) parameters precision optional an integer specifying the number of significant digits. return value a string representing a number object in fixed-point or exponential notation rounded to precision significant digits. see the discussion of rounding in the description of the number.prototype.tofixed() method, which also applies to toprecision(). if the precision argument is omitted, behaves as number.prototype.tostring(). if the precision argument is a non-integer value, it is rounded to the nearest integer. exceptions rangeerror if precision is not between 1 and 100 (inclusive), a rangeerror is thrown. implementations are allowed to support larger and smaller values as well. e...
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Number.prototype.toString() - JavaScript
ional. an integer in the range 2 through 36 specifying the base to use for representing numeric values. return value a string representing the specified number object. exceptions rangeerror if tostring() is given a radix less than 2 or greater than 36, a rangeerror is thrown. description the number object overrides the tostring() method of the object object. (it does not inherit object.prototype.tostring()). for number objects, the tostring() method returns a string representation of the object in the specified radix. the tostring() method parses its first argument, and attempts to return a string representation in the specified radix (base). for radices above 10, the letters of the alphabet indicate numerals greater than 9. for example, for hexadecimal numbers (base 16), a through f ar...
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Object.prototype.__lookupGetter__() - JavaScript
operty. description if a getter has been defined for an object's property, it's not possible to reference the getter function through that property, because that property refers to the return value of that function. __lookupgetter__ can be used to obtain a reference to the getter function. it is now possible to do this in a standardized way using object.getownpropertydescriptor() and object.getprototypeof(). examples standard-compliant and non-standard ways to get a property getter var obj = { get foo() { return math.random() > 0.5 ? 'foo' : 'bar'; } }; // non-standard and deprecated way obj.__lookupgetter__('foo'); // (function() { return math.random() > 0.5 ? 'foo' : 'bar'; }) // standard-compliant way object.getownpropertydescriptor(obj, "foo").get; // (function() { return math...
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Object.getPrototypeOf() - JavaScript
the object.getprototypeof() method returns the prototype (i.e. the value of the internal [[prototype]] property) of the specified object. the source for this interactive example is stored in a github repository. if you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request. syntax object.getprototypeof(obj) parameters obj the object whose prototype is to be returned. return value the prototype of the given object. if there are no inherited properties, null is returned. examples using getprototypeof var proto = {}; var obj = object.create(proto); object.getprototypeof(obj) === proto; // true non-object coercion in es5, it will throw a typeerror exception if the obj parameter isn't an object. in...
...urn value the prototype of the given object. if there are no inherited properties, null is returned. examples using getprototypeof var proto = {}; var obj = object.create(proto); object.getprototypeof(obj) === proto; // true non-object coercion in es5, it will throw a typeerror exception if the obj parameter isn't an object. in es2015, the parameter will be coerced to an object. object.getprototypeof('foo'); // typeerror: "foo" is not an object (es5 code) object.getprototypeof('foo'); // string.prototype (es2015 code) specifications specification ecmascript (ecma-262)the definition of 'object.getprototypeof' in that specification. ...

Object.prototype.toSource() - JavaScript
ource code is not available: function object() { [native code] } for instances of object, tosource() returns a string representing the source code. you can call tosource() while debugging to examine the contents of an object. overriding the tosource() method it is safe for objects to override the tosource() method. ...
...objects to override the tosource() method. for example: function person(name) { this.name = name; } person.prototype.tosource = function person_tosource() { return 'new person(' + uneval(this.name) + ')'; }; console.log(new person('joe').tosource()); // ---> new person("joe") built-in tosource() methods each core javascript type has its own tosource() method. these objects are: array.prototype.tosource() — array object. boolean.prototype.tosource() — boolean object. date.prototype.tosource() — date object. function.prototype.tosource() — function object. number.prototype.tosource() — number object. regexp.prototype.tosource() — regexp object. string.prototype.tosource() — string object. symbol.prototype.tosource() — symbol object. math.tosource() — ret...

RegExp.prototype[@@search]() - JavaScript
ase clone https://github.com/mdn/interactive-examples and send us a pull request. syntax regexp[symbol.search](str) parameters str a string that is a target of the search. return value integer if successful, [@@search]() returns the index of the first match of the regular expression inside the string. otherwise, it returns -1. description this method is called internally in string.prototype.search(). for example, the following two examples return the same result. 'abc'.search(/a/); /a/[symbol.search]('abc'); this method exists for customizing the search behavior in regexp subclasses. examples direct call this method can be used in almost the same way as string.prototype.search(), except the different this and the different arguments order. var re = /-/g; var str = '2016-01-02...
...h](str); console.log(result); // 4 using @@search in subclasses subclass of regexp can override [@@search]() method to modify the behavior. class myregexp extends regexp { constructor(str) { super(str) this.pattern = str; } [symbol.search](str) { return str.indexof(this.pattern); } } var re = new myregexp('a+b'); var str = 'ab a+b'; var result = str.search(re); // string.prototype.search calls re[@@search]. console.log(result); // 3 specifications specification ecmascript (ecma-262)the definition of 'regexp.prototype[@@search]' in that specification. ...

RegExp.prototype.dotAll - JavaScript
the dotall property indicates whether or not the "s" flag is used with the regular expression. dotall is a read-only property of an individual regular expression instance. property attributes of regexp.prototype.dotall writable no enumerable no configurable yes description the value of dotall is a boolean and true if the "s" flag was used; otherwise, false. the "s" flag indicates that the dot special character (".") should additionally match the following line terminator ("newline") characters in a string, which it would not match otherwise: u+000a line feed (lf) ("\n") u+000d carriage return (cr) ("\r") u+2028 line separator u+2029 paragraph separator this effectively means the dot will ma...
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RegExp.prototype.global - JavaScript
the "g" flag is used with the regular expression. global is a read-only property of an individual regular expression instance. the source for this interactive example is stored in a github repository. if you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request. property attributes of regexp.prototype.global writable no enumerable no configurable yes description the value of global is a boolean and true if the "g" flag was used; otherwise, false. the "g" flag indicates that the regular expression should be tested against all possible matches in a string. a regular expression defined as both global ("g") and stic...
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RegExp.prototype.ignoreCase - JavaScript
"i" flag is used with the regular expression. ignorecase is a read-only property of an individual regular expression instance. the source for this interactive example is stored in a github repository. if you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request. property attributes of regexp.prototype.ignorecase writable no enumerable no configurable yes description the value of ignorecase is a boolean and true if the "i" flag was used; otherwise, false. the "i" flag indicates that case should be ignored while attempting a match in a string. you cannot change this property directly. examples using ignorecase ...
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RegExp.prototype.multiline - JavaScript
"m" flag is used with the regular expression. multiline is a read-only property of an individual regular expression instance. the source for this interactive example is stored in a github repository. if you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request. property attributes of regexp.prototype.multiline writable no enumerable no configurable yes description the value of multiline is a boolean and is true if the "m" flag was used; otherwise, false. the "m" flag indicates that a multiline input string should be treated as multiple lines. for example, if "m" is used, "^" and "$" change from matching at only...
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RegExp.prototype.source - JavaScript
g containing the source text of the regexp object, and it doesn't contain the two forward slashes on both sides and any flags. the source for this interactive example is stored in a github repository. if you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request. property attributes of regexp.prototype.source writable no enumerable no configurable yes examples using source var regex = /foobar/ig; console.log(regex.source); // "foobar", doesn't contain /.../ and "ig". empty regular expressions and escaping starting with ecmascript 5, the source property no longer returns an empty string for empty regular expr...
...s an empty string for empty regular expressions. instead, the string "(?:)" is returned. in addition, line terminators (such as "\n") are escaped now. new regexp().source; // "(?:)" new regexp('\n').source === '\n'; // true, prior to es5 new regexp('\n').source === '\\n'; // true, starting with es5 specifications specification ecmascript (ecma-262)the definition of 'regexp.prototype.source' in that specification. ...

RegExp.prototype.sticky - JavaScript
the lastindex property of this regular expression). sticky is a read-only property of an individual regular expression object. the source for this interactive example is stored in a github repository. if you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request. property attributes of regexp.prototype.sticky writable no enumerable no configurable yes description the value of sticky is a boolean and true if the "y" flag was used; otherwise, false. the "y" flag indicates that it matches only from the index indicated by the lastindex property of this regular expression in the target string (and does not attempt to ...
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RegExp.prototype.test() - JavaScript
/mdn/interactive-examples and send us a pull request. syntax regexobj.test(str) parameters str the string against which to match the regular expression. returns true if there is a match between the regular expression and the string str. otherwise, false. description use test() whenever you want to know whether a pattern is found in a string. test() returns a boolean, unlike the string.prototype.search() method (which returns the index of a match, or -1 if not found). to get more information (but with slower execution), use the exec() method. (this is similar to the string.prototype.match() method.) as with exec() (or in combination with it), test() called multiple times on the same global regular expression instance will advance past the previous match. examples using test() simple...
...s a message which depends on the success of the test: function testinput(re, str) { let midstring; if (re.test(str)) { midstring = 'contains'; } else { midstring = 'does not contain'; } console.log(`${str} ${midstring} ${re.source}`); } using test() on a regex with the "global" flag when a regex has the global flag set, test() will advance the lastindex of the regex. (regexp.prototype.exec() also advances the lastindex property.) further calls to test(str) will resume searching str starting from lastindex. the lastindex property will continue to increase each time test() returns true. note: as long as test() returns true, lastindex will not reset—even when testing a different string! when test() returns false, the calling regex's lastindex property will reset to 0. th...

RegExp.prototype.toString() - JavaScript
teractive example is stored in a github repository. if you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request. syntax regexobj.tostring(); return value a string representing the given object. description the regexp object overrides the tostring() method of the object object; it does not inherit object.prototype.tostring(). for regexp objects, the tostring() method returns a string representation of the regular expression. examples using tostring() the following example displays the string value of a regexp object: var myexp = new regexp('a+b+c'); console.log(myexp.tostring()); // logs '/a+b+c/' var foo = new regexp('bar', 'g'); console.log(foo.tostring()); // logs '/bar/g' empty regular expre...
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RegExp.prototype.unicode - JavaScript
the "u" flag is used with a regular expression. unicode is a read-only property of an individual regular expression instance. the source for this interactive example is stored in a github repository. if you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request. property attributes of regexp.prototype.unicode writable no enumerable no configurable yes description the value of unicode is a boolean and true if the "u" flag was used; otherwise false. the "u" flag enables various unicode-related features. with the "u" flag, any unicode code point escapes will be interpreted as such, for example. you cannot change t...
...s various unicode-related features. with the "u" flag, any unicode code point escapes will be interpreted as such, for example. you cannot change this property directly. it is read-only. examples using the unicode property var regex = new regexp('\u{61}', 'u'); console.log(regex.unicode); // true specifications specification ecmascript (ecma-262)the definition of 'regexp.prototype.unicode' in that specification. ...

SharedArrayBuffer.prototype.slice() - JavaScript
the source for this interactive example is stored in a github repository. if you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request. syntax sab.slice() sab.slice(begin) sab.slice(begin, end) parameters begin optional zero-based index at which to begin extraction. ...
.... examples using slice var sab = new sharedarraybuffer(1024); sab.slice(); // sharedarraybuffer { bytelength: 1024 } sab.slice(2); // sharedarraybuffer { bytelength: 1022 } sab.slice(-2); // sharedarraybuffer { bytelength: 2 } sab.slice(0, 1); // sharedarraybuffer { bytelength: 1 } specifications specification ecmascript (ecma-262)the definition of 'sharedarraybuffer.prototype.slice' in that specification. ...

String.prototype.indexOf() - JavaScript
string object of the first occurrence of the specified value, starting the search at fromindex. returns -1 if the value is not found. the source for this interactive example is stored in a github repository. if you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request. note: for the array method, see array.prototype.indexof(). syntax str.indexof(searchvalue [, fromindex]) parameters searchvalue the string value to search for. if no string is explicitly provided, searchvalue will be coerced to "undefined", and this value will be searched for in str. so, for example: 'undefined'.indexof() will return 0, as undefined is found at position 0 in the string undefined. 'undefine'.indexof() however will...
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String.prototype.localeCompare() - JavaScript
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String.prototype.matchAll() - JavaScript
str = 'abc'; str.matchall(regexp); // typeerror matchall internally makes a clone of the regexp—so, unlike regexp.exec(), lastindex does not change as the string is scanned. const regexp = regexp('[a-c]','g'); regexp.lastindex = 1; const str = 'abc'; array.from(str.matchall(regexp), m => `${regexp.lastindex} ${m[0]}`); // array [ "1 b", "1 c" ] better access to capturing groups (than string.prototype.match()) another compelling reason for matchall is the improved access to capture groups. capture groups are ignored when using match() with the global /g flag: let regexp = /t(e)(st(\d?))/g; let str = 'test1test2'; str.match(regexp); // array ['test1', 'test2'] using matchall, you can access capture groups easily: let array = [...str.matchall(regexp)]; array[0]; // ['test1', 'e', 'st1', '...
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String.prototype.search() - JavaScript
ssed, it is implicitly converted to a regexp with new regexp(regexp). return value the index of the first match between the regular expression and the given string, or -1 if no match was found. description when you want to know whether a pattern is found, and also know its index within a string, use search(). (if you only want to know if it exists, use the similar test() method on the regexp prototype, which returns a boolean.) for more information (but slower execution) use match() (similar to the regular expression exec() method). examples using search() the following example searches a string with two different regex objects to show a successful search (positive value) vs. an unsuccessful search (-1) let str = "hey jude" let re = /[a-z]/g let redot = /[.]/g console.log(str.search(re))...
...ow a successful search (positive value) vs. an unsuccessful search (-1) let str = "hey jude" let re = /[a-z]/g let redot = /[.]/g console.log(str.search(re)) // returns 4, which is the index of the first capital letter "j" console.log(str.search(redot)) // returns -1 cannot find '.' dot punctuation specifications specification ecmascript (ecma-262)the definition of 'string.prototype.search' in that specification. ...

String.prototype.toLocaleLowerCase() - JavaScript
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String.prototype.toLocaleUpperCase() - JavaScript
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String.prototype.toUpperCase() - JavaScript
his interactive example is stored in a github repository. if you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request. syntax str.touppercase() return value a new string representing the calling string converted to upper case. exceptions typeerror when called on null or undefined, for example, string.prototype.touppercase.call(undefined). description the touppercase() method returns the value of the string converted to uppercase. this method does not affect the value of the string itself since javascript strings are immutable. examples basic usage console.log('alphabet'.touppercase()); // 'alphabet' conversion of non-string this values to strings this method will convert any non-string value t...
...ue of the string converted to uppercase. this method does not affect the value of the string itself since javascript strings are immutable. examples basic usage console.log('alphabet'.touppercase()); // 'alphabet' conversion of non-string this values to strings this method will convert any non-string value to a string, when you set its this to a value that is not a string: const a = string.prototype.touppercase.call({ tostring: function tostring() { return 'abcdef'; } }); const b = string.prototype.touppercase.call(true); // prints out 'abcdef true'. console.log(a, b); specifications specification ecmascript (ecma-262)the definition of 'string.prototype.touppercase' in that specification. ...

String.prototype.trim() - JavaScript
d send us a pull request. syntax str.trim() return value a new string representing the str stripped of whitespace from both ends. description the trim() method returns the string stripped of whitespace from both ends. trim() does not affect the value of the str itself. polyfill running the following code before any other code will create trim() if it's not natively available. if (!string.prototype.trim) { string.prototype.trim = function () { return this.replace(/^[\s\ufeff\xa0]+|[\s\ufeff\xa0]+$/g, ''); }; } examples using trim() the following example displays the lowercase string 'foo': var orig = ' foo '; console.log(orig.trim()); // 'foo' // another example of .trim() removing whitespace from just one side. var orig = 'foo '; console.log(orig.trim()); // 'foo' s...
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Symbol.prototype.description - JavaScript
of symbol objects. the source for this interactive example is stored in a github repository. if you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request. description symbol objects can be created with an optional description which can be used for debugging but not to access the symbol itself. the symbol.prototype.description property can be used to read that description. it is different to symbol.prototype.tostring() as it does not contain the enclosing "symbol()" string. see the examples. examples using description symbol('desc').tostring(); // "symbol(desc)" symbol('desc').description; // "desc" symbol('').description; // "" symbol().description; // undefined // well-known symbols sym...
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Symbol.prototype.toString() - JavaScript
e example is stored in a github repository. if you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request. syntax symbol().tostring() return value a string representing the specified symbol object. description the symbol object overrides the tostring method of the object object; it does not inherit object.prototype.tostring(). for symbol objects, the tostring method returns a string representation of the object. no string concatenation while you can call tostring() on symbols, you cannot use string concatenation with them: symbol('foo') + 'bar' // typeerror: can't convert symbol to string examples using tostring symbol('desc').tostring() // "symbol(desc)" // well-known symbols symbol.iterat...
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TypedArray.prototype.every() - JavaScript
typedarray is one of the typed array types here. the source for this interactive example is stored in a github repository. if you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request. ...
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TypedArray.prototype.filter() - JavaScript
typedarray is one of the typed array types here. the source for this interactive example is stored in a github repository. if you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request. syntax typedarray.filter(callback[, thisarg]) parameters callback function to test each element of the typed array. invoked with arguments (element, index, typedarray). ...
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TypedArray.prototype.forEach() - JavaScript
typedarray is one of the typed array types here. syntax typedarray.foreach(callback[, thisarg]) parameters callback function that produces an element of the new typed array, taking three arguments: currentvalue the current element being processed in the typed array. index the index of the current element being processed in the array. array the array foreach() was called upon. thisarg optional. value to use as this when executing callback. return value undefined. ...
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TypedArray.prototype.includes() - JavaScript
typedarray is one of the typed array types here. the source for this interactive example is stored in a github repository. if you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request. syntax typedarray.includes(searchelement[, fromindex]); parameters searchelement the element to search for. fromindex optional. ...
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TypedArray.prototype.indexOf() - JavaScript
typedarray is one of the typed array types here. the source for this interactive example is stored in a github repository. if you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request. syntax typedarray.indexof(searchelement[, fromindex = 0]) parameters searchelement element to locate in the typed array. ...
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TypedArray.prototype.lastIndexOf() - JavaScript
typedarray is one of the typed array types here. the source for this interactive example is stored in a github repository. if you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request. ...
...e ===, or triple-equals, operator). examples using lastindexof var uint8 = new uint8array([2, 5, 9, 2]); uint8.lastindexof(2); // 3 uint8.lastindexof(7); // -1 uint8.lastindexof(2, 3); // 3 uint8.lastindexof(2, 2); // 0 uint8.lastindexof(2, -2); // 0 uint8.lastindexof(2, -1); // 3 specifications specification ecmascript (ecma-262)the definition of 'typedarray.prototype.lastindexof' in that specification. ...

TypedArray.prototype.map() - JavaScript
typedarray is one of the typed array types here. the source for this interactive example is stored in a github repository. if you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request. ...
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TypedArray.prototype.reduceRight() - JavaScript
typedarray is one of the typed array types here. syntax typedarray.reduceright(callback[, initialvalue]) parameters callback function to execute on each value in the typed array, taking four arguments: previousvalue the value previously returned in the last invocation of the callback, or initialvalue, if supplied (see below). ...
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TypedArray.prototype.reverse() - JavaScript
the reverse() method reverses a typed array in place. the first typed array element becomes the last and the last becomes the first. this method has the same algorithm as array.prototype.reverse(). typedarray is one of the typed array types here. the source for this interactive example is stored in a github repository. if you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request. syntax typedarray.reverse(); return value the reversed array. ...
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TypedArray.prototype.sort() - JavaScript
the sort() method sorts the elements of a typed array numerically in place and returns the typed array. this method has the same algorithm as array.prototype.sort(), except that sorts the values numerically instead of as strings. typedarray is one of the typed array types here. the source for this interactive example is stored in a github repository. if you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request. syntax typedarray.sort([comparefunction]) parameters comparefunction optional specifies a function that defines the sort order. return value the sorted typed array. examples using sort for more examples, see also the array.prototype.sort() method. let numbers = new uint8array([40, 1, 5, ...
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TypedArray.prototype.toString() - JavaScript
typedarray is one of the typed array types here. the source for this interactive example is stored in a github repository. if you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request. syntax typedarray.tostring() return value a string representing the elements of the typed array. examples the typedarray objects override the tostring method of object. ...
... following code creates a typed array and uses tostring to convert the array to a string. var numbers = new uint8array([2, 5, 8, 1, 4]) numbers.tostring(); // "2,5,8,1,4" javascript calls the tostring method automatically when a typed array is to be represented as a text value or when an array is referred to in a string concatenation. compatibility if a browser doesn't support the typedarray.prototype.tostring() method yet, javascript will call the tostring method of object: var numbers = new uint8array([2, 5, 8, 1, 4]) numbers.tostring(); // "[object uint8array]" specifications specification ecmascript (ecma-262)the definition of 'array.prototype.tostring' in that specification. ...

WebAssembly.Table.prototype.get() - JavaScript
examples using get the following example (see table.html on github, and view it live also) compiles and instantiates the loaded table.wasm byte code using the webassembly.instantiatestreaming() method. it then retrieves the references stored in the exported table. ...
...e method of the webassembly.table() object retrieves a function reference stored at a given index. syntax table.get(index); parameters index the index of the function reference you want to retrieve. return value a function reference — this is an exported webassembly function, a javascript wrapper for an underlying wasm function. exceptions if index is greater than or equal to table.prototype.length, a rangeerror is thrown. examples using get the following example (see table.html on github, and view it live also) compiles and instantiates the loaded table.wasm byte code using the webassembly.instantiatestreaming() method. it then retrieves the references stored in the exported table. webassembly.instantiatestreaming(fetch('table.wasm')) .then(function(obj) { var tbl = obj.instan...

TextDecoder.prototype.decode() - Web APIs
syntax b1 = decoder.decode(buffer, options); b2 = decoder.decode(buffer); b3 = decoder.decode(); parameters buffer optional is either an arraybuffer or an arraybufferview containing the text to decode. options optional is a textdecodeoptions dictionary with the property: stream a boolean flag indicating that additional data will follow in subsequent calls to decode(). set to true if processing the data in chunks, and false for the final chunk or if the data is not chunked. it defaults to false. example this example encodes and decodes the euro symbol, €. ...

TextDecoder.prototype.encoding - Web APIs
it can be one of the following values: the recommended encoding for the web: 'utf-8'. the legacy single-byte encodings: 'ibm866', 'iso-8859-2', 'iso-8859-3', 'iso-8859-4', 'iso-8859-5', 'iso-8859-6', 'iso-8859-7', 'iso-8859-8'', 'iso-8859-8i', 'iso-8859-10', 'iso-8859-13', 'iso-8859-14', 'iso-8859-15', 'iso-8859-16', 'koi8-r', 'koi8-u', 'macintosh', 'windows-874', 'windows-1250', 'windows-1251', 'windows-1252', 'windows-1253', 'windows-1254', 'windows-1255', 'windows-1256', 'windows-1257', 'windows-1258', or 'x-mac-cyrillic'. the legacy multi-byte chinese (simplified) encodings: 'gbk', 'gb18030', and 'hz-gb-2312'. ...

TypeError: invalid Array.prototype.sort argument - JavaScript
the javascript exception "invalid array.prototype.sort argument" occurs when the argument of array.prototype.sort() isn't either undefined or a function which compares its operands. message typeerror: argument is not a function object (edge) typeerror: invalid array.prototype.sort argument (firefox) error type typeerror what went wrong? the argument of array.prototype.sort() is expected to be either undefined or a function which compares its operands. examples invalid cases [1, 3, 2].sort(5); // typeerror var cmp = { asc: (x, y) => x >= y, dsc: (x, y) => x <= y }; [1, 3, 2].sort(cmp[this.key] || 'asc'); // typeerror valid cases [1, 3, 2].sort(); // [1, 2, 3] var cmp = { asc: (x, y) => x >= y, dsc: (x, y) => x <= y }; [1, 3, 2].sort(cmp[this.key || 'asc']); // [1, 2, 3] ...

Array.prototype.concat() - JavaScript
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Array.prototype.entries() - JavaScript
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Array.prototype.flat() - JavaScript
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Array.prototype.join() - JavaScript
array four times: using the default separator, then a comma and a space, then a plus and an empty string. var a = ['wind', 'water', 'fire']; a.join(); // 'wind,water,fire' a.join(', '); // 'wind, water, fire' a.join(' + '); // 'wind + water + fire' a.join(''); // 'windwaterfire' joining an array-like object the following example joins array-like object (arguments), by calling function.prototype.call on array.prototype.join. function f(a, b, c) { var s = array.prototype.join.call(arguments); console.log(s); // '1,a,true' } f(1, 'a', true); //expected output: "1,a,true" specifications specification ecmascript (ecma-262)the definition of 'array.prototype.join' in that specification. ...

Array.prototype.keys() - JavaScript
send us a pull request. syntax arr.keys() return value a new array iterator object. examples key iterator doesn't ignore holes var arr = ['a', , 'c']; var sparsekeys = object.keys(arr); var densekeys = [...arr.keys()]; console.log(sparsekeys); // ['0', '2'] console.log(densekeys); // [0, 1, 2] specifications specification ecmascript (ecma-262)the definition of 'array.prototype.keys' in that specification. ...

Array.prototype.length - JavaScript
r); // [ 1, 2 ] arr.length = 5; // set array length to 5 while currently 2. console.log(arr); // [ 1, 2, <3 empty items> ] arr.foreach(element => console.log(element)); // 1 // 2 as you can see, the length property does not necessarily indicate the number of defined values in the array. see also relationship between length and numerical properties. property attributes of array.prototype.length writable yes enumerable no configurable no writable: if this attribute set to false, the value of the property cannot be changed. configurable: if this attribute set to false, any attempts to delete the property or change its attributes (writable, configurable, or enumerable) will fail. enumerable: if th...

Array.prototype.reverse() - JavaScript
console.log(a); // [3, 2, 1] reversing the elements in an array-like object the following example creates an array-like object a, containing three elements and a length property, then reverses the array-like object. the call to reverse() returns a reference to the reversed array-like object a. const a = {0: 1, 1: 2, 2: 3, length: 3}; console.log(a); // {0: 1, 1: 2, 2: 3, length: 3} array.prototype.reverse.call(a); //same syntax for using apply() console.log(a); // {0: 3, 1: 2, 2: 1, length: 3} specifications specification ecmascript (ecma-262)the definition of 'array.prototype.reverse' in that specification. ...

Array.prototype.sort() - JavaScript
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Array.prototype.splice() - JavaScript
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Array.prototype.toString() - JavaScript
ing each array element separated by commas. javascript calls the tostring method automatically when an array is to be represented as a text value or when an array is referred to in a string concatenation. ecmascript 5 semantics starting in javascript 1.8.5 (firefox 4), and consistent with ecmascript 5th edition semantics, the tostring() method is generic and can be used with any object. object.prototype.tostring() will be called, and the resulting value will be returned. examples using tostring const array1 = [1, 2, 'a', '1a']; console.log(array1.tostring()); // expected output: "1,2,a,1a" specifications specification ecmascript (ecma-262)the definition of 'array.prototype.tostring' in that specification. ...

Array.prototype.unshift() - JavaScript
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ArrayBuffer.prototype.byteLength - JavaScript
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ArrayBuffer.prototype.slice() - JavaScript
. the range specified by the begin and end parameters is clamped to the valid index range for the current array. if the computed length of the new arraybuffer would be negative, it is clamped to zero. examples copying an arraybuffer const buf1 = new arraybuffer(8); const buf2 = buf1.slice(0); specifications specification ecmascript (ecma-262)the definition of 'arraybuffer.prototype.slice' in that specification. ...

BigInt.prototype.valueOf() - JavaScript
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Boolean.prototype.valueOf() - JavaScript
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DataView.prototype.buffer - JavaScript
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DataView.prototype.byteLength - JavaScript
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DataView.prototype.byteOffset - JavaScript
ed and cannot be changed. examples using the byteoffset property var buffer = new arraybuffer(8); var dataview = new dataview(buffer); dataview.byteoffset; // 0 (no offset specified) var dataview2 = new dataview(buffer, 3); dataview2.byteoffset; // 3 (as specified when constructing the dataview) specifications specification ecmascript (ecma-262)the definition of 'dataview.prototype.byteoffset' in that specification. ...

DataView.prototype.getBigInt64() - JavaScript
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DataView.prototype.getBigUint64() - JavaScript
s set such that it would read beyond the end of the view. description there is no alignment constraint; multi-byte values may be fetched from any offset. examples using the getbiguint64 method var buffer = new arraybuffer(8); var dataview = new dataview(buffer); dataview.getbiguint64(0); // 0n specifications specification ecmascript (ecma-262)the definition of 'dataview.prototype.getbiguint64()' in that specification. ...

DataView.prototype.getFloat32() - JavaScript
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DataView.prototype.getFloat64() - JavaScript
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DataView.prototype.getInt16() - JavaScript
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DataView.prototype.getInt32() - JavaScript
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DataView.prototype.getInt8() - JavaScript
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DataView.prototype.getUint16() - JavaScript
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DataView.prototype.getUint32() - JavaScript
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DataView.prototype.getUint8() - JavaScript
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DataView.prototype.setBigInt64() - JavaScript
e undefined. errors thrown rangeerror thrown if the byteoffset is set such that it would store beyond the end of the view. examples using the setbigint64 method var buffer = new arraybuffer(8); var dataview = new dataview(buffer); dataview.setbigint64(0, 3n); dataview.getbigint64(0); // 3n specifications specification ecmascript (ecma-262)the definition of 'dataview.prototype.setbigint64()' in that specification. ...

DataView.prototype.setBigUint64() - JavaScript
undefined. errors thrown rangeerror thrown if the byteoffset is set such that it would store beyond the end of the view. examples using the setbiguint64 method var buffer = new arraybuffer(8); var dataview = new dataview(buffer); dataview.setbiguint64(0, 3n); dataview.getbiguint64(0); // 3n specifications specification ecmascript (ecma-262)the definition of 'dataview.prototype.setbiguint64()' in that specification. ...

DataView.prototype.setFloat32() - JavaScript
rn value undefined. errors thrown rangeerror thrown if the byteoffset is set such as it would store beyond the end of the view. examples using the setfloat32 method var buffer = new arraybuffer(8); var dataview = new dataview(buffer); dataview.setfloat32(1, 3); dataview.getfloat32(1); // 3 specifications specification ecmascript (ecma-262)the definition of 'dataview.prototype.setfloat32' in that specification. ...

DataView.prototype.setFloat64() - JavaScript
rn value undefined. errors thrown rangeerror thrown if the byteoffset is set such as it would store beyond the end of the view. examples using the setfloat64 method var buffer = new arraybuffer(8); var dataview = new dataview(buffer); dataview.setfloat64(0, 3); dataview.getfloat64(0); // 3 specifications specification ecmascript (ecma-262)the definition of 'dataview.prototype.setfloat64' in that specification. ...

DataView.prototype.setInt16() - JavaScript
return value undefined. errors thrown rangeerror thrown if the byteoffset is set such as it would store beyond the end of the view. examples using the setint16 method var buffer = new arraybuffer(8); var dataview = new dataview(buffer); dataview.setint16(1, 3); dataview.getint16(1); // 3 specifications specification ecmascript (ecma-262)the definition of 'dataview.prototype.setint16' in that specification. ...

DataView.prototype.setInt32() - JavaScript
return value undefined. errors thrown rangeerror thrown if the byteoffset is set such as it would store beyond the end of the view. examples using the setint32 method var buffer = new arraybuffer(8); var dataview = new dataview(buffer); dataview.setint32(1, 3); dataview.getint32(1); // 3 specifications specification ecmascript (ecma-262)the definition of 'dataview.prototype.setint32' in that specification. ...

DataView.prototype.setInt8() - JavaScript
t. return value undefined. errors thrown rangeerror thrown if the byteoffset is set such as it would store beyond the end of the view. examples using the setint8 method var buffer = new arraybuffer(8); var dataview = new dataview(buffer); dataview.setint8(1, 3); dataview.getint8(1); // 3 specifications specification ecmascript (ecma-262)the definition of 'dataview.prototype.setint8' in that specification. ...

DataView.prototype.setUint16() - JavaScript
eturn value undefined. errors thrown rangeerror thrown if the byteoffset is set such as it would store beyond the end of the view. examples using the setuint16 method var buffer = new arraybuffer(8); var dataview = new dataview(buffer); dataview.setuint16(1, 3); dataview.getuint16(1); // 3 specifications specification ecmascript (ecma-262)the definition of 'dataview.prototype.setuint16' in that specification. ...

DataView.prototype.setUint32() - JavaScript
eturn value undefined. errors thrown rangeerror thrown if the byteoffset is set such as it would store beyond the end of the view. examples using the setuint32 method var buffer = new arraybuffer(8); var dataview = new dataview(buffer); dataview.setuint32(1, 3); dataview.getuint32(1); // 3 specifications specification ecmascript (ecma-262)the definition of 'dataview.prototype.setuint32' in that specification. ...

DataView.prototype.setUint8() - JavaScript
return value undefined. errors thrown rangeerror thrown if the byteoffset is set such as it would store beyond the end of the view. examples using the setuint8 method var buffer = new arraybuffer(8); var dataview = new dataview(buffer); dataview.setuint8(1, 3); dataview.getuint8(1); // 3 specifications specification ecmascript (ecma-262)the definition of 'dataview.prototype.setuint8' in that specification. ...

Date.prototype[@@toPrimitive] - JavaScript
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Date.prototype.getDate() - JavaScript
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Date.prototype.getFullYear() - JavaScript
returns a four-digit number, for example, 1995. use this function to make sure a year is compliant with years after 2000. examples using getfullyear() the following example assigns the four-digit value of the current year to the variable year. var today = new date(); var year = today.getfullyear(); specifications specification ecmascript (ecma-262)the definition of 'date.prototype.getfullyear' in that specification. ...

Date.prototype.getHours() - JavaScript
or the given date according to local time. examples using gethours() the second statement below assigns the value 23 to the variable hours, based on the value of the date object xmas95. let xmas95 = new date('december 25, 1995 23:15:30'); let hours = xmas95.gethours(); console.log(hours); // 23 specifications specification ecmascript (ecma-262)the definition of 'date.prototype.gethours' in that specification. ...

Date.prototype.getMilliseconds() - JavaScript
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Date.prototype.getMinutes() - JavaScript
given date according to local time. examples using getminutes() the second statement below assigns the value 15 to the variable minutes, based on the value of the date object xmas95. var xmas95 = new date('december 25, 1995 23:15:30'); var minutes = xmas95.getminutes(); console.log(minutes); // 15 specifications specification ecmascript (ecma-262)the definition of 'date.prototype.getminutes' in that specification. ...

Date.prototype.getMonth() - JavaScript
intl.datetimeformat() with an options parameter. using this method, internationalization is made easier: var options = { month: 'long'}; console.log(new intl.datetimeformat('en-us', options).format(xmas95)); // december console.log(new intl.datetimeformat('de-de', options).format(xmas95)); // dezember specifications specification ecmascript (ecma-262)the definition of 'date.prototype.getmonth' in that specification. ...

Date.prototype.getSeconds() - JavaScript
given date according to local time. examples using getseconds() the second statement below assigns the value 30 to the variable seconds, based on the value of the date object xmas95. var xmas95 = new date('december 25, 1995 23:15:30'); var seconds = xmas95.getseconds(); console.log(seconds); // 30 specifications specification ecmascript (ecma-262)the definition of 'date.prototype.getseconds' in that specification. ...

Date.prototype.getTime() - JavaScript
alculate the executing time of some operations. see also date.now() to prevent instantiating unnecessary date objects. var end, start; start = new date(); for (var i = 0; i < 1000; i++) { math.sqrt(i); } end = new date(); console.log('operation took ' + (end.gettime() - start.gettime()) + ' msec'); specifications specification ecmascript (ecma-262)the definition of 'date.prototype.gettime' in that specification. ...

Date.prototype.getTimezoneOffset() - JavaScript
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Date.prototype.getUTCDate() - JavaScript
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Date.prototype.getUTCDay() - JavaScript
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Date.prototype.getUTCFullYear() - JavaScript
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Date.prototype.getUTCHours() - JavaScript
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Date.prototype.getUTCMilliseconds() - JavaScript
ix epoch time. to get total milliseconds since 1970/01/01, use the method ".gettime()". examples using getutcmilliseconds() the following example assigns the milliseconds portion of the current time to the variable milliseconds. var today = new date(); var milliseconds = today.getutcmilliseconds(); specifications specification ecmascript (ecma-262)the definition of 'date.prototype.getutcmilliseconds' in that specification. ...

Date.prototype.getUTCMinutes() - JavaScript
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Date.prototype.getUTCMonth() - JavaScript
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Date.prototype.getUTCSeconds() - JavaScript
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Date.prototype.getYear() - JavaScript
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Date.prototype.setDate() - JavaScript
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Date.prototype.setFullYear() - JavaScript
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Date.prototype.setHours() - JavaScript
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Date.prototype.setMilliseconds() - JavaScript
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Date.prototype.setMinutes() - JavaScript
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Date.prototype.setMonth() - JavaScript
turn 2nd march 2016. this is because in 2016 february had 29 days. examples using setmonth() var thebigday = new date(); thebigday.setmonth(6); //watch out for end of month transitions var endofmonth = new date(2016, 7, 31); endofmonth.setmonth(1); console.log(endofmonth); //wed mar 02 2016 00:00:00 specifications specification ecmascript (ecma-262)the definition of 'date.prototype.setmonth' in that specification. ...

Date.prototype.setSeconds() - JavaScript
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Date.prototype.setTime() - JavaScript
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Date.prototype.setUTCDate() - JavaScript
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Date.prototype.setUTCFullYear() - JavaScript
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Date.prototype.setUTCHours() - JavaScript
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Date.prototype.setUTCMilliseconds() - JavaScript
ate information in the date object accordingly. for example, if you use 1100 for millisecondsvalue, the seconds stored in the date object will be incremented by 1, and 100 will be used for milliseconds. examples using setutcmilliseconds() var thebigday = new date(); thebigday.setutcmilliseconds(500); specifications specification ecmascript (ecma-262)the definition of 'date.prototype.setutcmilliseconds' in that specification. ...

Date.prototype.setUTCMinutes() - JavaScript
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Date.prototype.setUTCMonth() - JavaScript
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Date.prototype.setUTCSeconds() - JavaScript
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Date.prototype.setYear() - JavaScript
year for dateobj is set to 1900 + yearvalue. otherwise, the year for dateobj is set to yearvalue. examples using setyear() the first two lines set the year to 1996. the third sets the year to 2000. var thebigday = new date(); thebigday.setyear(96); thebigday.setyear(1996); thebigday.setyear(2000); specifications specification ecmascript (ecma-262)the definition of 'date.prototype.setyear' in that specification. ...

Date.prototype.toDateString() - JavaScript
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Date.prototype.toGMTString() - JavaScript
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Date.prototype.toJSON() - JavaScript
g()) representing the date object's value. this method is generally intended to, by default, usefully serialize date objects during json serialization. examples using tojson() var jsondate = (new date()).tojson(); var backtodate = new date(jsondate); console.log(jsondate); //2015-10-26t07:46:36.611z specifications specification ecmascript (ecma-262)the definition of 'date.prototype.tojson' in that specification. ...

Date.prototype.toLocaleDateString() - JavaScript
.log(date.tolocaledatestring('de-de', options)); // → "donnerstag, 20. dezember 2012" // an application may want to use utc and make that visible options.timezone = 'utc'; options.timezonename = 'short'; console.log(date.tolocaledatestring('en-us', options)); // → "thursday, december 20, 2012, gmt" specifications specification ecmascript (ecma-262)the definition of 'date.prototype.tolocaledatestring' in that specification. ecmascript internationalization api (ecma-402)the definition of 'date.prototype.tolocaledatestring' in that specification. ...

Date.prototype.toTimeString() - JavaScript
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Date.prototype.toUTCString() - JavaScript
to the platform. the most common return value was an rfc-1123 formatted date stamp, which is a slightly updated version of rfc-822 date stamps. examples using toutcstring() let today = new date('wed, 14 jun 2017 00:00:00 pdt'); let utcstring = today.toutcstring(); // wed, 14 jun 2017 07:00:00 gmt specifications specification ecmascript (ecma-262)the definition of 'date.prototype.toutcstring' in that specification. ...

Date.prototype.valueOf() - JavaScript
method returns the primitive value of a date object. syntax dateobj.valueof() return value the number of milliseconds between 1 january 1970 00:00:00 utc and the given date. description the valueof() method returns the primitive value of a date object as a number data type, the number of milliseconds since midnight 01 january, 1970 utc. this method is functionally equivalent to the date.prototype.gettime() method. this method is usually called internally by javascript and not explicitly in code. examples using valueof() var x = new date(56, 6, 17); var myvar = x.valueof(); // assigns -424713600000 to myvar specifications specification ecmascript (ecma-262)the definition of 'date.prototype.valueof' in that specification. ...

Error.prototype.message - JavaScript
the message property is a human-readable description of the error. description this property contains a brief description of the error if one is available or has been set. spidermonkey makes extensive use of the message property for exceptions. the message property combined with the name property is used by the error.prototype.tostring() method to create a string representation of the error. by default, the message property is an empty string, but this behavior can be overridden for an instance by specifying a message as the first argument to the error constructor. examples throwing a custom error var e = new error('could not parse input'); // e.message is 'could not parse input' throw e; specifications specification ecmascript (ecma-262)the definition of 'error.prototyp...

Error.prototype.name - JavaScript
the name property represents a name for the type of error. the initial value is "error". description by default, error instances are given the name "error". the name property, in addition to the message property, is used by the error.prototype.tostring() method to create a string representation of the error. examples throwing a custom error var e = new error('malformed input'); // e.name is 'error' e.name = 'parseerror'; throw e; // e.tostring() would return 'parseerror: malformed input' specifications specification ecmascript (ecma-262)the definition of 'error.prototype.name' in that specification. ...

FinalizationRegistry.prototype.register() - JavaScript
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FinalizationRegistry.prototype.unregister() - JavaScript
eld by this `thingy` instance. */ release() { if (this.#file) { this.#registry.unregister(this.#file); // ^^^^^^^^^^−−−−− unregister token file.close(this.#file); this.#file = null; } } } specifications specification weakrefsthe definition of 'finalizationregistry.prototype.unregister' in that specification. ...

Function.prototype.call() - JavaScript
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Generator.prototype.next() - JavaScript
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Generator.prototype.return() - JavaScript
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Generator.prototype.throw() - JavaScript
h block as usual. function* gen() { while(true) { try { yield 42; } catch(e) { console.log('error caught!'); } } } const g = gen(); g.next(); // { value: 42, done: false } g.throw(new error('something went wrong')); // "error caught!" // { value: 42, done: false } specifications specification ecmascript (ecma-262)the definition of 'generator.prototype.throw' in that specification. ...

Intl.DateTimeFormat.prototype.formatRange() - JavaScript
the intl.datetimeformat.prototype.formatrange() formats a date range in the most concise way based on the locale and options provided when instantiating intl.datetimeformat object. the source for this interactive example is stored in a github repository. if you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request. syntax intl.datetimeformat.prototype.formatrange(startdate, enddate) examples basic formatrange usage this method receives two dates and formats the date range in the most concise way based on the locale and options provided when instantiating intl.datetimeformat. let date1 = new date(date.utc(2007, 0, 10, 10, 0, 0)); let date2 = new date(date.utc(2007, 0, 10, 11, 0, 0)); let date3 = new dat...

Intl.DateTimeFormat.prototype.formatRangeToParts() - JavaScript
the intl.datetimeformat.prototype.formatrangetoparts() method allows locale-specific tokens representing each part of the formatted date range produced by datetimeformat formatters. the source for this interactive example is stored in a github repository. if you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request. syntax intl.datetimeformat.prototype.formatrangetoparts(startdate, enddate) examples basic formatrangetoparts usage this method receives two dates and returns an array of objects containing the locale-specific tokens representing each part of the formatted date range. let date1 = new date(date.utc(2007, 0, 10, 10, 0, 0)); let date2 = new date(date.utc(2007, 0, 10, 11, 0, 0)); // > 'wed, 10 ...

Intl.DisplayNames.prototype.resolvedOptions() - JavaScript
syntax displaynames.resolvedoptions() return value an object with properties reflecting the locale and formatting options computed during the construction of the given displaynames object. description the object returned by resolvedoptions() has the following properties: locale the bcp 47 language tag for the locale actually used. if any unicode extension values were requested in the input bcp 47 language tag that led to this locale, the key-value pairs that were requested and are supported for this locale are included in locale. ...

Intl​.List​Format​.prototype​.resolvedOptions() - JavaScript
syntax listformat.resolvedoptions() return value an object with properties reflecting the locale and formatting options computed during the construction of the given listformat object. description the object returned by resolvedoptions() has the following properties: locale the bcp 47 language tag for the locale actually used. if any unicode extension values were requested in the input bcp 47 language tag that led to this locale, the key-value pairs that were requested and are supported for this locale are included in locale. ...

Intl.Locale.prototype.baseName - JavaScript
description an intl.locale object represents a parsed local and options for that locale. the basename property returns basic, core information about the locale in the form of a substring of the complete data string. specifically, the property returns the substring containing the language, and the script and region if available. basename returns the language ["-" script] ["-" region] *("-" variant) subsequence of the unicode_language_id grammar. ...

Intl.Locale.prototype.calendar - JavaScript
description the calendar property returns the part of the locale that indicates the locale's calendar era. while most of the world uses the gregorian calendar, there are several regional calendar eras used around the world. the following table shows all the valid unicode calendar key strings, along with a description of the calendar era they represent. ...

Intl.Locale.prototype.caseFirst - JavaScript
description a locale's collation rules are used to determine how strings are ordered in that locale. certain locales use a character's case (uppercase or lowercase) in the collation process. this additional rule can be expressed in a locale's casefirst property. there are 3 values that the casefirst property can have, outlined in the table below. casefirst values value description upper upper case to be sorted before lower case. lower lower case to be sorted before upper case. false no special case ordering. ...

Intl.Locale.prototype.collation - JavaScript
description collation is the process of ordering strings of characters. it is used whenever strings must be sorted and placed into a certain order, from search query results to ordering records in a database. while the idea of placing strings in order might seem trivial, the idea of order can vary from region to region and language to language. the collation property helps to make it easier for javascript programmers to access the collation type used by a particular locale. below is a table with the available collation types, taken from the unicode collation specification. ...

Intl.Locale.prototype.hourCycle - JavaScript
description there are 2 main types of time keeping conventions (clocks) used around the world: the 12 hour clock and the 24 hour clock. the hourcycle property makes it easier for javascript programmers to access the clock type used by a particular locale. like other additional locale data, hour cycle type is an extension subtag, which extends the data contained in a locale string. the hour cycle type can have several different values, which are listed in the table below. valid hour cycle types hour cycle type description h12 hour system using 1–12; corresponds to 'h' in patterns. ...

Intl.Locale.prototype.language - JavaScript
description language is one of the core features of a locale. the unicode specification treats the language identifier of a locale as the language and the region together (to make a distiction between dialects and variations, e.g. british english vs. american english). the language property of a locale returns strictly the locale's language subtag. examples setting the language in the locale identifer string argument in order to be a valid unicode locale identifier, a string must start with the language subtag. ...

Intl.Locale.prototype.maximize() - JavaScript
the source for this interactive example is stored in a github repository. if you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request. syntax locale.maximize() return value a locale instance whose basename property returns the result of the add likely subtags algorithm executed against locale.basename. description sometimes, it is convenient to be able to identify the most likely locale language identifier subtags based on an incomplete langauage id. the add likely subtags algorithm gives us this functionality. ...

Intl.Locale.prototype.minimize() - JavaScript
the source for this interactive example is stored in a github repository. if you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request. syntax locale.minimize() return value a locale instance whose basename property returns the result of the remove likely subtags algorithm executed against locale.basename. description this method carries out the reverse of maximize(), removing any language, script, or region subtags from the locale language identifier (essentially the contents of basename). ...

Intl.Locale.prototype.numberingSystem - JavaScript
description a numeral system is a system for expressing numbers. the numberingsystem property helps to represent the different numeral systems used by various countries, regions, and cultures around the world. as with most internationalization schemas, the numeral systems that can be represented in a locale object by numberingsystem are standardized by unicode. a table of the standard unicode numeral systems can be seen below. ...

Intl.Locale.prototype.numeric - JavaScript
description like intl.locale.casefirst, numeric represents a modification to the collation rules utilized by the locale. numeric is a boolean value, which means that it can be either true or false. if numeric is set to false, there will be no special handling of numeric values in strings. if numeric is set to true, then the locale will take numeric characters into account when collating strings. this special numeric handling means that sequences of decimal digits will be compared as numbers. for example, the string "a-21" will be considered less than "a-123". ...

Intl.Locale.prototype.region - JavaScript
description the region is an essential part of the locale identifier, as it places the locale in a specific area of the world. knowing the locale's region is vital to identifying differences between locales. for example, english is spoken in the united kingdom and the united states of america, but there are differences in spelling and other language conventions between those two countries. knowing the locale's region helps javascript programmers make sure that the content from their sites and applications is correctly displayed when viewed from different areas of the world. ...

Intl.Locale.prototype.script - JavaScript
description a script, sometimes called writing system, is one of the core attributes of a locale. it indicates the set of symbols, or glyphs, that are used to write a particular language. for instance, the script associated with english is latin, whereas the script typically associated with korean is hangul. in many cases, denoting a script is not strictly necessary, since the language (which is necessary) is only written in a single script. there are exceptions to this rule, however, and it is important to indicate the script whenever possible, in order to have a complete unicode language identifier. ...

Intl.Locale.prototype.toString() - JavaScript
the source for this interactive example is stored in a github repository. if you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request. syntax locale.tostring() return value the locale's unicode locale identifier string. description the locale object is a javascript representation of a concept unicode locale identifier. information about a particular locale (language, script, calendar type, etc.) can be encoded in a locale identifier string. to make it easier to work with these locale identifiers, the locale object was introduced to javascript. ...

Intl.RelativeTimeFormat.prototype.format() - JavaScript
the source for this interactive example is stored in a github repository. if you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request. syntax relativetimeformat.format(value, unit) parameters value numeric value to use in the internationalized relative time message. unit unit to use in the relative time internationalized message. possible values are: "year", "quarter", "month", "week", "day", "hour", "minute", "second". plural forms are also permitted. ...

Intl.RelativeTimeFormat.prototype.resolvedOptions() - JavaScript
the source for this interactive example is stored in a github repository. if you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request. syntax relativetimeformat.resolvedoptions() return value a new object with properties reflecting the locale and number formatting options computed during the initialization of the given relativetimeformat object. ...

Map.prototype[@@iterator]() - JavaScript
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Map.prototype[@@toStringTag] - JavaScript
the map[@@tostringtag] property has an initial value of "map". the source for this interactive example is stored in a github repository. if you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request. property attributes of map.prototype[@@tostringtag] writable no enumerable no configurable yes syntax map[symbol.tostringtag] examples using tostringtag object.prototype.tostring.call(new map()) // "[object map]" specifications specification ecmascript (ecma-262)the definition of 'map.prototype[@@tostringtag]' in that specification. ...

Map.prototype.clear() - JavaScript
ctive-examples and send us a pull request. syntax mymap.clear(); return value undefined. examples using clear() var mymap = new map(); mymap.set('bar', 'baz'); mymap.set(1, 'foo'); mymap.size; // 2 mymap.has('bar'); // true mymap.clear(); mymap.size; // 0 mymap.has('bar') // false specifications specification ecmascript (ecma-262)the definition of 'map.prototype.clear' in that specification. ...

Map.prototype.delete() - JavaScript
n the map object existed and has been removed, or false if the element does not exist. examples using delete() var mymap = new map(); mymap.set('bar', 'foo'); mymap.delete('bar'); // returns true. successfully removed. mymap.has('bar'); // returns false. the "bar" element is no longer present. specifications specification ecmascript (ecma-262)the definition of 'map.prototype.delete' in that specification. ecmascript 2015 (6th edition, ecma-262)the definition of 'map.prototype.delete' in that specification. ...

Map.prototype.entries() - JavaScript
t. examples using entries() let mymap = new map() mymap.set('0', 'foo') mymap.set(1, 'bar') mymap.set({}, 'baz') let mapiter = mymap.entries() console.log(mapiter.next().value) // ["0", "foo"] console.log(mapiter.next().value) // [1, "bar"] console.log(mapiter.next().value) // [object, "baz"] specifications specification ecmascript (ecma-262)the definition of 'map.prototype.entries' in that specification. ...

Map.prototype.forEach() - JavaScript
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Map.prototype.get() - JavaScript
nt to return from the map object. return value the element associated with the specified key, or undefined if the key can't be found in the map object. examples using get() let mymap = new map(); mymap.set('bar', 'foo'); mymap.get('bar'); // returns "foo" mymap.get('baz'); // returns undefined specifications specification ecmascript (ecma-262)the definition of 'map.prototype.get' in that specification. ...

Map.prototype.has() - JavaScript
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Map.prototype.keys() - JavaScript
value a new map iterator object. examples using keys() var mymap = new map(); mymap.set('0', 'foo'); mymap.set(1, 'bar'); mymap.set({}, 'baz'); var mapiter = mymap.keys(); console.log(mapiter.next().value); // "0" console.log(mapiter.next().value); // 1 console.log(mapiter.next().value); // object specifications specification ecmascript (ecma-262)the definition of 'map.prototype.keys' in that specification. ...

Map.prototype.set() - JavaScript
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Map.prototype.size - JavaScript
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Map.prototype.values() - JavaScript
a new map iterator object. examples using values() var mymap = new map(); mymap.set('0', 'foo'); mymap.set(1, 'bar'); mymap.set({}, 'baz'); var mapiter = mymap.values(); console.log(mapiter.next().value); // "foo" console.log(mapiter.next().value); // "bar" console.log(mapiter.next().value); // "baz" specifications specification ecmascript (ecma-262)the definition of 'map.prototype.values' in that specification. ...

Number.prototype.toExponential() - JavaScript
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Number.prototype.valueOf() - JavaScript
r object. description this method is usually called internally by javascript and not explicitly in web code. examples using valueof let numobj = new number(10) console.log(typeof numobj) // object let num = numobj.valueof() console.log(num) // 10 console.log(typeof num) // number specifications specification ecmascript (ecma-262)the definition of 'number.prototype.valueof' in that specification. ...

Object.prototype.__defineGetter__() - JavaScript
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Object.prototype.__defineSetter__() - JavaScript
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Object.prototype.__lookupSetter__() - JavaScript
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Promise.prototype.finally() - JavaScript
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RegExp.prototype.compile() - JavaScript
compile method is deprecated. you can just use the regexp constructor to achieve the same effect. examples using compile() the following example shows how to recompile a regular expression with a new pattern and a new flag. var regexobj = new regexp('foo', 'gi'); regexobj.compile('new foo', 'g'); specifications specification ecmascript (ecma-262)the definition of 'regexp.prototype.compile' in that specification. ...

RegExp.prototype.exec() - JavaScript
match in a specified string. returns a result array, or null. javascript regexp objects are stateful when they have the global or sticky flags set (e.g. /foo/g or /foo/y). they store a lastindex from the previous match. using this internally, exec() can be used to iterate over multiple matches in a string of text (with capture groups), as opposed to getting just the matching strings with string.prototype.match(). a newer function has been proposed to simplify matching multiple parts of a string (with capture groups): string.prototype.matchall(). if you are executing a match simply to find true or false, use regexp.prototype.test() method or string.prototype.search() instead. the source for this interactive example is stored in a github repository. if you'd like to contribute to the interacti...

Set.prototype[@@iterator]() - JavaScript
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Set.prototype.add() - JavaScript
l request. syntax myset.add(value); parameters value the value of the element to add to the set object. return value the set object. examples using the add method var myset = new set(); myset.add(1); myset.add(5).add('some text'); // chainable console.log(myset); // set [1, 5, "some text"] specifications specification ecmascript (ecma-262)the definition of 'set.prototype.add' in that specification. ...

Set.prototype.clear() - JavaScript
interactive-examples and send us a pull request. syntax myset.clear(); return value undefined. examples using the clear method var myset = new set(); myset.add(1); myset.add('foo'); myset.size; // 2 myset.has('foo'); // true myset.clear(); myset.size; // 0 myset.has('bar') // false specifications specification ecmascript (ecma-262)the definition of 'set.prototype.clear' in that specification. ...

Set.prototype.delete() - JavaScript
n object from a set. const setobj = new set(); // create a new set. setobj.add({x: 10, y: 20}); // add object in the set. setobj.add({x: 20, y: 30}); // add object in the set. // delete any point with `x > 10`. setobj.foreach(function(point){ if (point.x > 10){ setobj.delete(point) } }) specifications specification ecmascript (ecma-262)the definition of 'set.prototype.delete' in that specification. ...

Set.prototype.entries() - JavaScript
order. examples using entries() var myset = new set(); myset.add('foobar'); myset.add(1); myset.add('baz'); var setiter = myset.entries(); console.log(setiter.next().value); // ["foobar", "foobar"] console.log(setiter.next().value); // [1, 1] console.log(setiter.next().value); // ["baz", "baz"] specifications specification ecmascript (ecma-262)the definition of 'set.prototype.entries' in that specification. ...

Set.prototype.forEach() - JavaScript
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Set.prototype.has() - JavaScript
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Set.prototype.size - JavaScript
pull request. description the value of size is an integer representing how many entries the set object has. a set accessor function for size is undefined; you cannot change this property. examples using size var myset = new set(); myset.add(1); myset.add(5); myset.add('some text') myset.size; // 3 specifications specification ecmascript (ecma-262)the definition of 'set.prototype.size' in that specification. ...

Set.prototype.values() - JavaScript
in the given set, in insertion order. examples using values() var myset = new set(); myset.add('foo'); myset.add('bar'); myset.add('baz'); var setiter = myset.values(); console.log(setiter.next().value); // "foo" console.log(setiter.next().value); // "bar" console.log(setiter.next().value); // "baz" specifications specification ecmascript (ecma-262)the definition of 'set.prototype.values' in that specification. ...

SharedArrayBuffer.prototype.byteLength - JavaScript
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String.prototype[@@iterator]() - JavaScript
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String.prototype.anchor() - JavaScript
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String.prototype.big() - JavaScript
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String.prototype.blink() - JavaScript
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String.prototype.bold() - JavaScript
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String.prototype.charAt() - JavaScript
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String.prototype.charCodeAt() - JavaScript
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String.prototype.concat() - JavaScript
t('kevin', '. have a nice day.')) // hello, kevin. have a nice day. let greetlist = ['hello', ' ', 'venkat', '!'] "".concat(...greetlist) // "hello venkat!" "".concat({}) // [object object] "".concat([]) // "" "".concat(null) // "null" "".concat(true) // "true" "".concat(4, 5) // "45" specifications specification ecmascript (ecma-262)the definition of 'string.prototype.concat' in that specification. ...

String.prototype.fixed() - JavaScript
<tt> html element. description the fixed() method embeds a string in a <tt> tag: "<tt>str</tt>". examples using fixed() the following example uses the fixed method to change the formatting of a string: var worldstring = 'hello, world'; console.log(worldstring.fixed()); // "<tt>hello, world</tt>" specifications specification ecmascript (ecma-262)the definition of 'string.prototype.fixed' in that specification. ...

String.prototype.fontcolor() - JavaScript
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String.prototype.fontsize() - JavaScript
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String.prototype.italics() - JavaScript
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String.prototype.lastIndexOf() - JavaScript
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String.prototype.link() - JavaScript
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String.prototype.normalize() - JavaScript
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String.prototype.padEnd() - JavaScript
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String.prototype.padStart() - JavaScript
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String.prototype.replace() - JavaScript
e f2c() function. f2c() then returns the celsius number. this function approximates perl's s///e flag. function f2c(x) { function convert(str, p1, offset, s) { return ((p1 - 32) * 5/9) + 'c'; } let s = string(x); let test = /(-?\d+(?:\.\d*)?)f\b/g; return s.replace(test, convert); } specifications specification ecmascript (ecma-262)the definition of 'string.prototype.replace' in that specification. ...

String.prototype.replaceAll() - JavaScript
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String.prototype.slice() - JavaScript
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String.prototype.small() - JavaScript
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String.prototype.split() - JavaScript
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String.prototype.strike() - JavaScript
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String.prototype.sub() - JavaScript
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String.prototype.substring() - JavaScript
p if olds is itself a substring of news — for example, if you attempted to replace 'world' with 'otherworld' here. a better method for replacing strings is as follows: function replacestring(olds, news, fulls) { return fulls.split(olds).join(news) } the code above serves as an example for substring operations. if you need to replace substrings, most of the time you will want to use string.prototype.replace(). specifications specification ecmascript (ecma-262)the definition of 'string.prototype.substring' in that specification. ...

String.prototype.sup() - JavaScript
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String.prototype.toLowerCase() - JavaScript
senting the calling string converted to lower case. description the tolowercase() method returns the value of the string converted to lower case. tolowercase() does not affect the value of the string str itself. examples using tolowercase() console.log('alphabet'.tolowercase()); // 'alphabet' specifications specification ecmascript (ecma-262)the definition of 'string.prototype.tolowercase' in that specification. ...

String.prototype.toString() - JavaScript
the tostring() method returns a string representing the specified object. syntax str.tostring() return value a string representing the calling object. description the string object overrides the tostring() method of the object object; it does not inherit object.prototype.tostring(). for string objects, the tostring() method returns a string representation of the object and is the same as the string.prototype.valueof() method. examples using tostring() the following example displays the string value of a string object: var x = new string('hello world'); console.log(x.tostring()); // logs 'hello world' specifications specification ecmascript (ecma-262)the definition of 'string.prototype.tostring' in that specification. ...

String.prototype.valueOf() - JavaScript
the valueof() method returns the primitive value of a string object. syntax str.valueof() return value a string representing the primitive value of a given string object. description the valueof() method of string returns the primitive value of a string object as a string data type. this value is equivalent to string.prototype.tostring(). this method is usually called internally by javascript and not explicitly in code. examples using valueof() var x = new string('hello world'); console.log(x.valueof()); // displays 'hello world' specifications specification ecmascript (ecma-262)the definition of 'string.prototype.valueof' in that specification. ...

Symbol.prototype[@@toPrimitive] - JavaScript
n object to a primitive value. you rarely need to invoke the [@@toprimitive]() method yourself; javascript automatically invokes it when encountering an object where a primitive value is expected. examples using @@toprimitive const sym = symbol("example"); sym === sym[symbol.toprimitive](); // true specifications specification ecmascript (ecma-262)the definition of 'symbol.prototype.@@toprimitive' in that specification. ...

Symbol.prototype.valueOf() - JavaScript
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TypedArray.prototype[@@iterator]() - JavaScript
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TypedArray.prototype.buffer - JavaScript
his property. the value is established when the typedarray is constructed and cannot be changed. typedarray is one of the typedarray objects. examples using the buffer property var buffer = new arraybuffer(8); var uint16 = new uint16array(buffer); uint16.buffer; // arraybuffer { bytelength: 8 } specifications specification ecmascript (ecma-262)the definition of 'typedarray.prototype.buffer' in that specification. ...

TypedArray.prototype.byteLength - JavaScript
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TypedArray.prototype.byteOffset - JavaScript
is one of the typedarray objects. examples using the byteoffset property var buffer = new arraybuffer(8); var uint8 = new uint8array(buffer); uint8.byteoffset; // 0 (no offset specified) var uint8 = new uint8array(buffer, 3); uint8.byteoffset; // 3 (as specified when constructing uint8array) specifications specification ecmascript (ecma-262)the definition of 'typedarray.prototype.byteoffset' in that specification. ...

TypedArray.prototype.entries() - JavaScript
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TypedArray.prototype.find() - JavaScript
there is no prime number). function isprime(element, index, array) { var start = 2; while (start <= math.sqrt(element)) { if (element % start++ < 1) { return false; } } return element > 1; } var uint8 = new uint8array([4, 5, 8, 12]); console.log(uint8.find(isprime)); // 5 specifications specification ecmascript (ecma-262)the definition of '%typedarray%.prototype.find' in that specification. ...

TypedArray.prototype.keys() - JavaScript
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TypedArray.prototype.length - JavaScript
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TypedArray.prototype.set() - JavaScript
ex 0). exceptions a rangeerror, if the offset is set such as it would store beyond the end of the typed array. examples using set() var buffer = new arraybuffer(8); var uint8 = new uint8array(buffer); uint8.set([1, 2, 3], 3); console.log(uint8); // uint8array [ 0, 0, 0, 1, 2, 3, 0, 0 ] specifications specification ecmascript (ecma-262)the definition of 'typedarray.prototype.set' in that specification. ...

TypedArray.prototype.subarray() - JavaScript
inal object and vice versa. examples using the subarray method var buffer = new arraybuffer(8); var uint8 = new uint8array(buffer); uint8.set([1,2,3]); console.log(uint8); // uint8array [ 1, 2, 3, 0, 0, 0, 0, 0 ] var sub = uint8.subarray(0,4); console.log(sub); // uint8array [ 1, 2, 3, 0 ] specifications specification ecmascript (ecma-262)the definition of 'typedarray.prototype.subarray' in that specification. ...

TypedArray.prototype.values() - JavaScript
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WeakMap.prototype.delete() - JavaScript
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WeakMap.prototype.get() - JavaScript
akmap object. return value the element associated with the specified key in the weakmap object. if the key can't be found, undefined is returned. examples using the get method var wm = new weakmap(); wm.set(window, 'foo'); wm.get(window); // returns "foo". wm.get('baz'); // returns undefined. specifications specification ecmascript (ecma-262)the definition of 'weakmap.prototype.get' in that specification. ...

WeakMap.prototype.has() - JavaScript
resence in the weakmap object. return value boolean returns true if an element with the specified key exists in the weakmap object; otherwise false. examples using the has method var wm = new weakmap(); wm.set(window, 'foo'); wm.has(window); // returns true wm.has('baz'); // returns false specifications specification ecmascript (ecma-262)the definition of 'weakmap.prototype.has' in that specification. ...

WeakMap.prototype.set() - JavaScript
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WeakRef.prototype.deref() - JavaScript
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WeakSet.prototype.add() - JavaScript
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WeakSet.prototype.delete() - JavaScript
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WeakSet.prototype.has() - JavaScript
the weakset. return value boolean returns true if an element with the specified value exists in the weakset object; otherwise false. examples using the has method var ws = new weakset(); var obj = {}; ws.add(window); myset.has(window); // returns true myset.has(obj); // returns false specifications specification ecmascript (ecma-262)the definition of 'weakset.prototype.has' in that specification. ...

WebAssembly.Instance.prototype.exports - JavaScript
instance.exports examples using exports after fetching some webassembly bytecode using fetch, we compile and instantiate the module using the webassembly.instantiatestreaming() function, importing a javascript function into the webassembly module in the process. we then call an exported webassembly function that is exported by the instance. ...

WebAssembly.Memory.prototype.buffer - JavaScript
examples using buffer the following example (see memory.html on github, and view it live also) fetches and instantiates the loaded memory.wasm byte code using the webassembly.instantiatestreaming() method, while importing the memory created in the line above. it then stores some values in that memory, then exports a function and uses it to sum some values. ...

WebAssembly.Table.prototype.grow() - JavaScript
syntax table.grow(number); parameters number the number of elements you want to grow the table by. return value the previous length of the table. exceptions if the grow() operation fails for whatever reason, a rangeerror is thrown. examples using grow the following example creates a new webassembly table instance with an initial size of 2 and a maximum size of 10. ...

WebAssembly.Table.prototype.length - JavaScript
the number of elements in the table. syntax table.length; examples using length the following example creates a new webassembly table instance with an initial size of 2 and a maximum size of 10. var table = new webassembly.table({ element: "anyfunc", initial: 2, maximum: 10 }); you can then grow the table by 1 with the following: console.log(table.length); // "2" console.log(table.grow(1)); // "2" console.log(table.length); // "3" specifications specification webassembly javascript interfacethe definition of 'length' in that specification. browser compatibility the compatibility table on this page is generated from structured data. ...

Details of the object model - JavaScript
« previousnext » javascript is an object-based language based on prototypes, rather than being class-based. because of this different basis, it can be less apparent how javascript allows you to create hierarchies of objects and to have inheritance of properties and their values. this chapter attempts to clarify the situation. this chapter assumes that you are already somewhat familiar with javascript and that you have used javascript functions to create simple objects. class-based vs. prototype-based languages class-based object-oriented languages, such as java and c++, are founded on the concept of two distinct entities: classes and instances. a class defines all of the properties that characterize a certain set of objects (considering methods and fields in java, or member...
...ar member in a set of objects it describes. for example, the employee class could represent the set of all employees. an instance, on the other hand, is the instantiation of a class; that is. for example, victoria could be an instance of the employee class, representing a particular individual as an employee. an instance has exactly the same properties of its parent class (no more, no less). ...
...all employees. an instance, on the other hand, is the instantiation of a class; that is. for example, victoria could be an instance of the employee class, representing a particular individual as an employee. an instance has exactly the same properties of its parent class (no more, no less). a prototype-based language, such as javascript, does not make this distinction: it simply has objects. a prototype-based language has the notion of a prototypical object, an object used as a template from which to get the initial properties for a new object. any object can specify its own properties, either when you create it or at run time. in addition, any object can be associated as the prototype for another object, allowing the second object to share the first object's properties. defining a class in cl...
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Linear-gradient Generator - CSS: Cascading Style Sheets
(); color.sethsv(h, s, v); return color; } function hsvacolor(h, s, v, a) { var color = new color(); color.sethsv(h, s, v); color.a = a; return color; } function hslcolor(h, s, l) { var color = new color(); color.sethsl(h, s, l); return color; } function hslacolor(h, s, l, a) { var color = new color(); color.sethsl(h, s, l); color.a = a; return color; } color.prototype.copy = function copy(obj) { if(obj instanceof color !== true) { console.log('typeof parameter not color'); return; } this.r = obj.r; this.g = obj.g; this.b = obj.b; this.a = obj.a; this.hue = obj.hue; this.saturation = obj.saturation; this.value = obj.value; this.format = '' + obj.format; this.lightness = obj.lightness; }; color.prototype.setformat = function setfo...
... this.a = obj.a; this.hue = obj.hue; this.saturation = obj.saturation; this.value = obj.value; this.format = '' + obj.format; this.lightness = obj.lightness; }; color.prototype.setformat = function setformat(format) { if (format === 'hsv') this.format = 'hsv'; if (format === 'hsl') this.format = 'hsl'; }; /*========== methods to set color properties ==========*/ color.prototype.isvalidrgbvalue = function isvalidrgbvalue(value) { return (typeof(value) === 'number' && isnan(value) === false && value >= 0 && value <= 255); }; color.prototype.setrgba = function setrgba(red, green, blue, alpha) { if (this.isvalidrgbvalue(red) === false || this.isvalidrgbvalue(green) === false || this.isvalidrgbvalue(blue) === false) return; this.r = red | 0; this.g ...
... && value >= 0 && value <= 255); }; color.prototype.setrgba = function setrgba(red, green, blue, alpha) { if (this.isvalidrgbvalue(red) === false || this.isvalidrgbvalue(green) === false || this.isvalidrgbvalue(blue) === false) return; this.r = red | 0; this.g = green | 0; this.b = blue | 0; if (this.isvalidrgbvalue(alpha) === true) this.a = alpha | 0; }; color.prototype.setbyname = function setbyname(name, value) { if (name === 'r' || name === 'g' || name === 'b') { if(this.isvalidrgbvalue(value) === false) return; this[name] = value; this.updatehsx(); } }; color.prototype.sethsv = function sethsv(hue, saturation, value) { this.hue = hue; this.saturation = saturation; this.value = value; this.hsvtorgb(); }; color.prototype.sethsl ...
...And 53 more matches

Color picker tool - CSS: Cascading Style Sheets
(); color.sethsv(h, s, v); return color; } function hsvacolor(h, s, v, a) { var color = new color(); color.sethsv(h, s, v); color.a = a; return color; } function hslcolor(h, s, l) { var color = new color(); color.sethsl(h, s, l); return color; } function hslacolor(h, s, l, a) { var color = new color(); color.sethsl(h, s, l); color.a = a; return color; } color.prototype.copy = function copy(obj) { if(obj instanceof color !== true) { console.log('typeof parameter not color'); return; } this.r = obj.r; this.g = obj.g; this.b = obj.b; this.a = obj.a; this.hue = obj.hue; this.saturation = obj.saturation; this.value = obj.value; this.format = '' + obj.format; this.lightness = obj.lightness; }; color.prototype.setformat = function setfo...
... this.a = obj.a; this.hue = obj.hue; this.saturation = obj.saturation; this.value = obj.value; this.format = '' + obj.format; this.lightness = obj.lightness; }; color.prototype.setformat = function setformat(format) { if (format === 'hsv') this.format = 'hsv'; if (format === 'hsl') this.format = 'hsl'; }; /*========== methods to set color properties ==========*/ color.prototype.isvalidrgbvalue = function isvalidrgbvalue(value) { return (typeof(value) === 'number' && isnan(value) === false && value >= 0 && value <= 255); }; color.prototype.setrgba = function setrgba(red, green, blue, alpha) { if (this.isvalidrgbvalue(red) === false || this.isvalidrgbvalue(green) === false || this.isvalidrgbvalue(blue) === false) return; this.r = red | 0; this.g ...
... && value >= 0 && value <= 255); }; color.prototype.setrgba = function setrgba(red, green, blue, alpha) { if (this.isvalidrgbvalue(red) === false || this.isvalidrgbvalue(green) === false || this.isvalidrgbvalue(blue) === false) return; this.r = red | 0; this.g = green | 0; this.b = blue | 0; if (this.isvalidrgbvalue(alpha) === true) this.a = alpha | 0; }; color.prototype.setbyname = function setbyname(name, value) { if (name === 'r' || name === 'g' || name === 'b') { if(this.isvalidrgbvalue(value) === false) return; this[name] = value; this.updatehsx(); } }; color.prototype.sethsv = function sethsv(hue, saturation, value) { this.hue = hue; this.saturation = saturation; this.value = value; this.hsvtorgb(); }; color.prototype.sethsl ...
...And 40 more matches

JavaScript Daemons Management - Archive of obsolete content
s.rate = math.floor(nrate); } if (nlen > 0) { this.length = math.floor(nlen); } if (fonstart) { this.onstart = fonstart; } if (finit) { this.onstop = finit; finit.call(oowner, this.index, this.length, this.backw); } } /* create the daemon.blank() constructor and the global daemon.context object */ daemon.blank = function () {}; daemon.context = daemon.blank.prototype; /* make love with the gc :-) */ daemon.blank.prototype = /* important! */ daemon.prototype; daemon.context.constructor = object; /* these properties can be manually reconfigured after the creation of the daemon */ daemon.prototype.owner = daemon.context; daemon.prototype.task = null; daemon.prototype.rate = 100; daemon.prototype.length = infinity; daemon.prototype.reversals =...
...e with the gc :-) */ daemon.blank.prototype = /* important! ...
....prototype = /* important! ...
...And 34 more matches

Index
d that does not need to be marked for gc from jspropertyspec::name or jsfunctionspec::name. the resulting jsid, on success, is either an interned string or a well-known symbol; either way it is immune to gc so there is no need to visit *idp during gc marking.. 64 js::protokeytoid jsapi reference, reference, référence(2), spidermonkey js::protokeytoid converts a specified js prototype key key, to a js id. js::protokeytoid stores a jsid to *idp. 65 js::remove*root jsapi reference, obsolete, reference, référence(2), spidermonkey js::remove*root removes the variable that rp points to from the garbage collector's root set. 66 js::rooted jsapi reference, reference, référence(2), spidermonkey here, ptr represents the private member of js...
...e macros providing equivalent functionality are deprecated. 126 jsnewenumerateop jsapi reference, reference, référence(2), spidermonkey from spidermonkey 38, jsnewenumerateop is the type of objectops::enumerate. this callback overrides a portion of spidermonkey's default [[enumerate]] internal method. when an ordinary object is enumerated, that object and each object on its prototype chain is tested for an enumerate op, and those ops are called in order. the properties each op adds to the properties vector are added to the set of values the for-in loop will iterate over. all of this is nonstandard. 127 jsnewresolveop jsapi reference, obsolete, spidermonkey like jsresolveop, but flags provide contextual information about the property access. 128 ...
...e infallible, so required slots must be pre-allocated, or implementations must suppress out-of-memory errors. the native ops (js_objectops, see js/src/jsobj.cpp) access slots reserved by including a call to the jsclass_has_reserved_slots(n) macro in the jsclass.flags initializer. 138 jsobjectops.lookupproperty jsapi reference, obsolete, spidermonkey look for id in obj and its prototype chain, returning js_false on error or exception, js_true on success. on success, return null in *propp if id was not found. if id was found, return the first object searching from obj along its prototype chain in which id names a direct property in *objp, and return a non-null, opaque property pointer in *propp. 139 jsobjectops.newobjectmap jsapi reference, obsolete, spidermonkey ...
...And 29 more matches

String - JavaScript
a constructor, which is usually more useful. static methods string.fromcharcode(num1 [, ...[, numn]]) returns a string created by using the specified sequence of unicode values. string.fromcodepoint(num1 [, ...[, numn) returns a string created by using the specified sequence of code points. string.raw() returns a string created from a raw template string. ...
......[, numn]]) returns a string created by using the specified sequence of unicode values. string.fromcodepoint(num1 [, ...[, numn) returns a string created by using the specified sequence of code points. string.raw() returns a string created from a raw template string. instance properties string.prototype.length reflects the length of the string. read-only. instance methods string.prototype.charat(index) returns the character (exactly one utf-16 code unit) at the specified index. ...
...nt(num1 [, ...[, numn) returns a string created by using the specified sequence of code points. string.raw() returns a string created from a raw template string. instance properties string.prototype.length reflects the length of the string. read-only. instance methods string.prototype.charat(index) returns the character (exactly one utf-16 code unit) at the specified index. string.prototype.charcodeat(index) returns a number that is the utf-16 code unit value at the given index. ...
...And 23 more matches

New in JavaScript 1.3 - Archive of obsolete content
1.3. note that communicator and navigator 4.0-4.05 and earlier ignored scripts with the language attribute set to "javascript1.3" and higher. <script language="javascript1.2"> <!-- javascript for navigator 4.0. --> <script language="javascript1.3"> <!-- javascript for navigator 4.5. ...
... and navigator 4.0-4.05 and earlier ignored scripts with the language attribute set to "javascript1.3" and higher. <script language="javascript1.2"> <!-- javascript for navigator 4.0. --> <script language="javascript1.3"> <!-- javascript for navigator 4.5. ...
...ignored scripts with the language attribute set to "javascript1.3" and higher. <script language="javascript1.2"> <!-- javascript for navigator 4.0. --> <script language="javascript1.3"> <!-- javascript for navigator 4.5. ...
...And 21 more matches

Object - JavaScript
the object class represents one of javascript's data types. it is used to store various keyed collections and more complex entities. objects can be created using the object() constructor or the object initializer / literal syntax. description nearly all objects in javascript are instances of object; a typical object inherits properties (including methods) from object.prototype, although these properties may be shadowed (a.k.a. ...
...yntax. description nearly all objects in javascript are instances of object; a typical object inherits properties (including methods) from object.prototype, although these properties may be shadowed (a.k.a. overridden). however, an object may be deliberately created for which this is not true (e.g. by object.create(null)), or it may be altered so that this is no longer true (e.g. with object.setprototypeof). changes to the object prototype object are seen by all objects through prototype chaining, unless the properties and methods subject to those changes are overridden further along the prototype chain. this provides a very powerful although potentially dangerous mechanism to override or extend object behavior. the object constructor creates an object wrapper for the given value. if the val...
...ise, it will return an object of a type that corresponds to the given value. if the value is an object already, it will return the value. when called in a non-constructor context, object behaves identically to new object(). see also the object initializer / literal syntax. deleting a property from an object there isn't any method in an object itself to delete its own properties (such as map.prototype.delete()). to do so, one must use the delete operator. constructor object() creates a new object object. it is a wrapper for the given value. static methods object.assign() copies the values of all enumerable own properties from one or more source objects to a target object. object.create() creates a new object with the specified prototype object and properties. object.definepropert...
...And 21 more matches

Classes and Inheritance - Archive of obsolete content
not have native support for classical inheritance. instead, it uses something called prototypal inheritance. as it turns out, it is possible to emulate classical inheritance using prototypal inheritance, but not without writing a significant amount of boilerplate code. classes in javascript are defined using constructor functions. ...
...ossible to emulate classical inheritance using prototypal inheritance, but not without writing a significant amount of boilerplate code. classes in javascript are defined using constructor functions. each constructor function has an associated object, known as its prototype, which is shared between all instances of that class. we will show how to define classes using constructors, and how to use prototypes to efficiently define member functions on each instance. classical inheritance can be implemented in javascript using constructors and prototypes. we will show how to make inheritance work correctly with respect to constructors, prototypes, and the instanceof operator, and how to override methods in subclasses. the sdk uses a special constructor internally, known as class, to create constructors...
...ly legal to perform ordinary function calls on them. in fact, some people (including the add-on sdk team) prefer to use constructors this way. however, since the value of this is undefined for ordinary function calls, we need to add some boilerplate code to convert them to constructor calls: function shape(x, y) { if (!this) return new shape(x, y); this.x = x; this.y = y; } prototypes every object has an implicit property, known as its prototype. when javascript looks for a property, it first looks for it in the object itself. if it cannot find the property there, it looks for it in the object's prototype. if the property is found on the prototype, the lookup succeeds, and javascript pretends that it found the property on the original object. every function has an explicit p...
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Box-shadow generator - CSS: Cascading Style Sheets
ibe, unsubscribe : unsubscribe } })(); window.addeventlistener("load", function(){ boxshadow.init(); }); var boxshadow = (function boxshadow() { function getelembyid(id) { return document.getelementbyid(id); } /** * rgba color class */ function color() { this.r = 0; this.g = 0; this.b = 0; this.a = 1; this.hue = 0; this.saturation = 0; this.value = 0; } color.prototype.copy = function copy(obj) { if(obj instanceof color !== true) { console.log("typeof instance not color"); return; } this.r = obj.r; this.g = obj.g; this.b = obj.b; this.a = obj.a; this.hue = obj.hue; this.saturation = obj.saturation; this.value = obj.value; } color.prototype.setrgba = function setrgba(red, green, blue, alpha) { if (red != undefined) this.r = red |...
...rototype.setrgba = function setrgba(red, green, blue, alpha) { if (red != undefined) this.r = red | 0; if (green != undefined) this.g = green | 0; if (blue != undefined) this.b = blue | 0; if (alpha != undefined) this.a = alpha | 0; } /** * hsv/hsb (hue, saturation, value / brightness) * @param hue 0-360 * @param saturation 0-100 * @param value 0-100 */ color.prototype.sethsv = function sethsv(hue, saturation, value) { this.hue = hue; this.saturation = saturation; this.value = value; this.updatergb(); } color.prototype.updatergb = function updatergb() { var sat = this.saturation / 100; var value = this.value / 100; var c = sat * value; var h = this.hue / 60; var x = c * (1 - math.abs(h % 2 - 1)); var m = value - c; var precision = 255; ...
... + m) * precision; m = m * precision; if (h >= 0 && h < 1) { this.setrgba(c, x, m); return; } if (h >= 1 && h < 2) { this.setrgba(x, c, m); return; } if (h >= 2 && h < 3) { this.setrgba(m, c, x); return; } if (h >= 3 && h < 4) { this.setrgba(m, x, c); return; } if (h >= 4 && h < 5) { this.setrgba(x, m, c); return; } if (h >= 5 && h < 6) { this.setrgba(c, m, x); return; } } color.prototype.updatehsv = function updatehsv() { var red = this.r / 255; var green = this.g / 255; var blue = this.b / 255; var cmax = math.max(red, green, blue); var cmin = math.min(red, green, blue); var delta = cmax - cmin; var hue = 0; var saturation = 0; if (delta) { if (cmax === red ) { hue = ((green - blue) / delta); } if (cmax === green ) { hue = 2 + (blue - red) / delta; } ...
...And 18 more matches

TypedArray - JavaScript
es and methods that can be used with any typed array containing elements of any type. the source for this interactive example is stored in a github repository. if you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request. ...
... the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request. description ecmascript 2015 defines a typedarray constructor that serves as the [[prototype]] of all typedarray constructors. this constructor is not directly exposed: there is no global %typedarray% or typedarray property. it is only directly accessible through object.getprototypeof(int8array) and similar. all typedarrays constructors inherit common properties from the %typedarray% constructor function. additionally, all typed array prototypes (typedarray.prototype) have %typedarray%.prototype as their [[prototype]]. the %typedarray% constructor on its own is not particularly useful. calling it or using it in a new expression will throw a typeerror, except when used du...
...ypedarray% is only useful to polyfill functions or properties onto all typedarray constructors. when creating an instance of a typedarray (e.g. int8array), an array buffer is created internally in memory or, if an arraybuffer object is given as constructor argument, then this is used instead. the buffer address is saved as an internal property of the instance and all the methods of %typedarray%.prototype, i.e. set value and get value etc., operate on that array buffer address. typedarray objects type value range size in bytes description web idl type equivalent c type int8array -128 to 127 1 8-bit two's complement signed integer byte int8_t uint8array 0 to 255 1 8-bit unsigned integer octet uint8_t uint8clamped...
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core/heritage - Archive of obsolete content
s of machinery being exposed: // defining a simple class function dog(name) { // classes are for creating instances, calling them without `new` changes // behavior, which in majority cases you need to handle, so you end up // with additional boilerplate. ...
...are for creating instances, calling them without `new` changes // behavior, which in majority cases you need to handle, so you end up // with additional boilerplate. if (!(this instanceof dog)) return new dog(name); this.name = name; }; // to define methods you need to make a dance with a special 'prototype' // property of the constructor function. this is too much machinery exposed. ...
...calling them without `new` changes // behavior, which in majority cases you need to handle, so you end up // with additional boilerplate. if (!(this instanceof dog)) return new dog(name); this.name = name; }; // to define methods you need to make a dance with a special 'prototype' // property of the constructor function. this is too much machinery exposed. ...
...And 17 more matches

Date - JavaScript
january, 1970, 00:00:00 utc, with leap seconds ignored. note: parsing of strings with date.parse is strongly discouraged due to browser differences and inconsistencies. date.utc() accepts the same parameters as the longest form of the constructor (i.e. 2 to 7) and returns the number of milliseconds since january 1, 1970, 00:00:00 utc, with leap seconds ignored. ...
...iscouraged due to browser differences and inconsistencies. date.utc() accepts the same parameters as the longest form of the constructor (i.e. 2 to 7) and returns the number of milliseconds since january 1, 1970, 00:00:00 utc, with leap seconds ignored. instance methods date.prototype.getdate() returns the day of the month (1–31) for the specified date according to local time. date.prototype.getday() returns the day of the week (0–6) for the specified date according to local time. ...
... longest form of the constructor (i.e. 2 to 7) and returns the number of milliseconds since january 1, 1970, 00:00:00 utc, with leap seconds ignored. instance methods date.prototype.getdate() returns the day of the month (1–31) for the specified date according to local time. date.prototype.getday() returns the day of the week (0–6) for the specified date according to local time. date.prototype.getfullyear() returns the year (4 digits for 4-digit years) of the specified date according to local time. date.prototype.gethours() returns the hour (0–23) in the specified date according to local time. ...
...And 16 more matches

Property cache
c,dec}prop or prop{inc,dec}. nor do operations such as add that only need to look up a property (.tostring) in unusual cases. throughout this article, phrases such as "own property" should be taken to refer to the low-level representation of properties in scopes and shape chains. in the case of shared permanent properties, this differs from the notion of "own property" seen by scripts via object.prototype.hasownproperty. shape native objects have a shape, a 24-bit unsigned integer such that: basic layout guarantee — if at time t0 the object x has shape s and at time t1 the object y has shape s, and no shape-regenerating gc occurred, then y at t1 has the same jsclass, jsobjectops, prototype, and property specs as x had at t0. to be more precise regarding property specs, y's properties hav...
...ty specs as x had at t0. to be more precise regarding property specs, y's properties have the same names, getters, setters, property attributes, and slot offsets, and they are in the same order, as x's properties at t0. furthermore, y at t1 has the same number of fixed slots that x had at t0, and either both have a slot array or neither does. ...
...recise regarding property specs, y's properties have the same names, getters, setters, property attributes, and slot offsets, and they are in the same order, as x's properties at t0. furthermore, y at t1 has the same number of fixed slots that x had at t0, and either both have a slot array or neither does. ...
...And 15 more matches

Object.create() - JavaScript
the object.create() method creates a new object, using an existing object as the prototype of the newly created object. the source for this interactive example is stored in a github repository. if you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request. syntax object.create(proto, [propertiesobject]) parameters proto the object which should be the prototype of the newly-created object. propertiesobject optional if specified and not undefined, an object whose enumerable own properties (that is, those properties defined upon itself and not enumerable properties along its prototype chain) specify property descriptors to be added to the newly-created object, with the corresponding property names. thes...
... exceptions the proto parameter has to be either null or an object excluding primitive wrapper objects. if proto is neither of these a typeerror is thrown. ...
... // create "null" object (same as before) ocn.tostring = object.tostring; // since new object lacks method then try assigning it directly from standard-object > ocn.tostring // shows "tostring() { [native code] }" -- missing method seems to be there now > ocn.tostring == object.tostring // shows "true" -- method seems to be same as the standard object-method > ocn.tostring() // error: function.prototype.tostring requires that 'this' be a function adding the missing object-method directly to new object's "prototype" does not work either, since the new object does not have a real prototype (which is really the cause of all these problems) and one cannot be directly added: ocn = object.create( null ); // create "null" object (same as before) ocn.prototype.tostring = object.tostring; // error:...
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Inheritance in JavaScript - Learn web development
prerequisites: basic computer literacy, a basic understanding of html and css, familiarity with javascript basics (see first steps and building blocks) and oojs basics (see introduction to objects). objective: to understand how it is possible to implement inheritance in javascript. prototypal inheritance so far we have seen some inheritance in action — we have seen how prototype chains work, and how members are inherited going up a chain. but mostly this has involved built-in browser functions. how do we create an object in javascript that inherits from another object? let's explore how to do this with a concrete example. getting started first of all, make yourself a local copy of our oojs-class-inheritance-start.html file (see it running live also). inside here you'l...
...he same person() constructor example that we've been using all the way through the module, with a slight difference — we've defined only the properties inside the constructor: function person(first, last, age, gender, interests) { this.name = { first, last }; this.age = age; this.gender = gender; this.interests = interests; }; the methods are all defined on the constructor's prototype. for example: person.prototype.greeting = function() { alert('hi! i\'m ' + this.name.first + '.'); }; note: in the source code, you'll also see bio() and farewell() methods defined. later you'll see how these can be inherited by other constructors. say we wanted to create a teacher class, like the one we described in our initial object-oriented definition, which inherits all the members fr...
...herit the width and height properties by doing this (as well as the other steps described below, of course): function blueglassbrick() { brick.call(this); this.opacity = 0.5; this.color = 'blue'; } note that we've only specified this inside call() — no other parameters are required as we are not inheriting any properties from the parent that are set via parameters. ...
...And 14 more matches

A re-introduction to JavaScript (JS tutorial) - JavaScript
ronments like gnome (one of the most popular guis for gnu/linux operating systems), and others. overview javascript is a multi-paradigm, dynamic language with types and operators, standard built-in objects, and methods. its syntax is based on the java and c languages — many structures from those languages apply to javascript as well. javascript supports object-oriented programming with object prototypes, instead of classes (see more about prototypical inheritance and es2015 classes). javascript also supports functional programming — because they are objects, functions may be stored in variables and passed around like any other object. let's start off by looking at the building blocks of any language: the types. javascript programs manipulate values, and those values all belong to a type. jav...
...ld be preferred at all times. object literal syntax can be used to initialize an object in its entirety: var obj = { name: 'carrot', for: 'max', // 'for' is a reserved word, use '_for' instead. details: { color: 'orange', size: 12 } }; attribute access can be chained together: obj.details.color; // orange obj['details']['size']; // 12 the following example creates an object prototype(person) and an instance of that prototype(you). function person(name, age) { this.name = name; this.age = age; } // define an object var you = new person('you', 24); // we are creating a new person named "you" aged 24. once created, an object's properties can again be accessed in one of two ways: // dot notation obj.name = 'simon'; var name = obj.name; and... // bracket notation obj[...
...ed to set and get properties with names that are reserved words: obj.for = 'simon'; // syntax error, because 'for' is a reserved word obj['for'] = 'simon'; // works fine starting in ecmascript 5, reserved words may be used as object property names "in the buff". this means that they don't need to be "clothed" in quotes when defining object literals. see the es5 spec. for more on objects and prototypes see object.prototype. for an explanation of object prototypes and the object prototype chains see inheritance and the prototype chain. starting in ecmascript 2015, object keys can be defined by the variable using bracket notation upon being created. {[phonetype]: 12345} is possible instead of just var userphone = {}; userphone[phonetype] = 12345. arrays arrays in javascript are actually a s...
...And 13 more matches

Uint8ClampedArray - JavaScript
string value of the constructor name. in the case of the uint8clampedarray type: "uint8clampedarray". static methods uint8clampedarray.from() creates a new uint8clampedarray from an array-like or iterable object. see also array.from(). uint8clampedarray.of() creates a new uint8clampedarray from a variable number of arguments. see also array.of(). ...
...() creates a new uint8clampedarray from an array-like or iterable object. see also array.from(). uint8clampedarray.of() creates a new uint8clampedarray from a variable number of arguments. see also array.of(). instance properties uint8clampedarray.prototype.buffer returns the arraybuffer referenced by the uint8clampedarray fixed at construction time and thus read only. uint8clampedarray.prototype.bytelength returns the length (in bytes) of the uint8clampedarray from the start of its arraybuffer. ...
...of arguments. see also array.of(). instance properties uint8clampedarray.prototype.buffer returns the arraybuffer referenced by the uint8clampedarray fixed at construction time and thus read only. uint8clampedarray.prototype.bytelength returns the length (in bytes) of the uint8clampedarray from the start of its arraybuffer. fixed at construction time and thus read only. uint8clampedarray.prototype.byteoffset returns the offset (in bytes) of the uint8clampedarray from the start of its arraybuffer. fixed at construction time and thus read only. uint8clampedarray.prototype.length returns the number of elements hold in the uintclamped8array. fixed at construction time and thus read only. ...
...And 12 more matches

Array - JavaScript
neither the length of a javascript array nor the types of its elements are fixed. since an array's length can change at any time, and data can be stored at non-contiguous locations in the array, javascript arrays are not guaranteed to be dense; this depends on how the programmer chooses to use them. ...
... the constructor function is used to create derived objects. static methods array.from() creates a new array instance from an array-like or iterable object. array.isarray() returns true if the argument is an array, or false otherwise. array.of() creates a new array instance with a variable number of arguments, regardless of number or type of the arguments. ...
...methods array.from() creates a new array instance from an array-like or iterable object. array.isarray() returns true if the argument is an array, or false otherwise. array.of() creates a new array instance with a variable number of arguments, regardless of number or type of the arguments. instance properties array.prototype.length reflects the number of elements in an array. ...
...And 11 more matches

BigInt64Array - JavaScript
y.name returns the string value of the constructor name. in the case of the bigint64array type, this is "bigint64array". static methods bigint64array.from() creates a new bigint64array from an array-like or iterable object. see also array.from(). bigint64array.of() creates a new bigint64array with a variable number of arguments. see also array.of(). ...
...int64array.from() creates a new bigint64array from an array-like or iterable object. see also array.from(). bigint64array.of() creates a new bigint64array with a variable number of arguments. see also array.of(). instance properties bigint64array.prototype.buffer returns the arraybuffer referenced by the bigint64array. this is fixed at construction time and thus read only. bigint64array.prototype.bytelength returns the length (in bytes) of the bigint64array from the start of its arraybuffer. ...
...er of arguments. see also array.of(). instance properties bigint64array.prototype.buffer returns the arraybuffer referenced by the bigint64array. this is fixed at construction time and thus read only. bigint64array.prototype.bytelength returns the length (in bytes) of the bigint64array from the start of its arraybuffer. this is fixed at construction time and thus read only. bigint64array.prototype.byteoffset returns the offset (in bytes) of the bigint64array from the start of its arraybuffer. this is fixed at construction time and thus read only. bigint64array.prototype.length returns the number of elements hold in the bigint64array. this is fixed at construction time and thus read only. ...
...And 11 more matches

BigUint64Array - JavaScript
returns the string value of the constructor name. in the case of the biguint64array type this is "biguint64array". static methods biguint64array.from() creates a new biguint64array from an array-like or iterable object. see also array.from(). biguint64array.of() creates a new biguint64array with a variable number of arguments. see also array.of(). ...
...rray.from() creates a new biguint64array from an array-like or iterable object. see also array.from(). biguint64array.of() creates a new biguint64array with a variable number of arguments. see also array.of(). instance properties biguint64array.prototype.buffer returns the arraybuffer referenced by the biguint64array. this is fixed at construction time and thus read only. biguint64array.prototype.bytelength returns the length (in bytes) of the biguint64array from the start of its arraybuffer. ...
... arguments. see also array.of(). instance properties biguint64array.prototype.buffer returns the arraybuffer referenced by the biguint64array. this is fixed at construction time and thus read only. biguint64array.prototype.bytelength returns the length (in bytes) of the biguint64array from the start of its arraybuffer. this is fixed at construction time and thus read only. biguint64array.prototype.byteoffset returns the offset (in bytes) of the biguint64array from the start of its arraybuffer. this is fixed at construction time and thus read only. biguint64array.prototype.length returns the number of elements hold in the biguint64array. this is fixed at construction time and thus read only. ...
...And 11 more matches

jspage - Archive of obsolete content
var mootools={version:"1.2.4",build:"0d9113241a90b9cd5643b926795852a2026710d4"};var native=function(k){k=k||{};var a=k.name;var i=k.legacy;var b=k.protect; var c=k.implement;var h=k.generics;var f=k.initialize;var g=k.afterimplement||function(){};var d=f||i;h=h!==false;d.constructor=native;d.$family={name:"native"}; if(i&&f){d.prototype=i.prototype;}d.prototype.constructor=d;if(a){var e=a.tolowercase();d.prototype.$family={name:e};native.typize(d,e);}var j=function(n,l,o,m){if(!b||m||!n.prototype[l]){n.prototype[l]=o; }if(h){native.genericize(n,l,b);}g.call(n,l,o);return n;};d.alias=function(n,l,p){if(typeof n=="string"){var o=this.prototype[n];if((n=o)){return j(this,l,n,p); }}for(var m in n){this.alias(m,n[m],l);}return this;};d.implement=function(m,l,o){if(typeof m=="string"){return j(th...
...b);}g.call(n,l,o);return n;};d.alias=function(n,l,p){if(typeof n=="string"){var o=this.prototype[n];if((n=o)){return j(this,l,n,p); }}for(var m in n){this.alias(m,n[m],l);}return this;};d.implement=function(m,l,o){if(typeof m=="string"){return j(this,m,l,o);}for(var n in m){j(this,n,m[n],l); }return this;};if(c){d.implement(c);}return d;};native.genericize=function(b,c,a){if((!a||!b[c])&&typeof b.prototype[c]=="function"){b[c]=function(){var d=array.prototype.slice.call(arguments); return b.prototype[c].apply(d.shift(),d);};}};native.implement=function(d,c){for(var b=0,a=d.length;b<a;b++){d[b].implement(c);}};native.typize=function(a,b){if(!a.type){a.type=function(c){return($type(c)===b); };}};(function(){var a={array:array,date:date,function:function,number:number,regexp:regexp,string:string};for(...
...nproperty(a)){b[a]=this[a];}}return b;},getlength:function(){var b=0;for(var a in this){if(this.hasownproperty(a)){b++; }}return b;}});hash.alias("foreach","each");array.implement({foreach:function(c,d){for(var b=0,a=this.length;b<a;b++){c.call(d,this[b],b,this);}}});array.alias("foreach","each"); function $a(b){if(b.item){var a=b.length,c=new array(a);while(a--){c[a]=b[a];}return c;}return array.prototype.slice.call(b);}function $arguments(a){return function(){return arguments[a]; };}function $chk(a){return !!(a||a===0);}function $clear(a){cleartimeout(a);clearinterval(a);return null;}function $defined(a){return(a!=undefined);}function $each(c,b,d){var a=$type(c); ((a=="arguments"||a=="collection"||a=="array")?array:hash).each(c,b,d);}function $empty(){}function $extend(c,a){for(var b in (a||{})){...
...And 10 more matches

ECMAScript 2015 support in Mozilla - Archive of obsolete content
l assembly. it will also appear as the international industry standard iso/iec 16262:2016. a pdf and html version of the standard can be freely downloaded on ecma-international.org. a channel for feedback on ecmascript standards is es-discuss. ...
...e international industry standard iso/iec 16262:2016. a pdf and html version of the standard can be freely downloaded on ecma-international.org. a channel for feedback on ecmascript standards is es-discuss. ...
... standard iso/iec 16262:2016. a pdf and html version of the standard can be freely downloaded on ecma-international.org. a channel for feedback on ecmascript standards is es-discuss. ...
...And 10 more matches

Element.classList - Web APIs
(...cls); div.classlist.remove(...cls); // replace class "foo" with class "bar" div.classlist.replace("foo", "bar"); versions of firefox before 26 do not implement the use of several arguments in the add/remove/toggle methods. ...
...ds. see https://bugzilla.mozilla.org/show_bug.cgi?id=814014 polyfill the legacy onpropertychange event can be used to create a living classlist mockup thanks to a element.prototype.classname property that fires the specified event once it is changed. the following polyfill for both classlist and domtokenlist ensures full compliance (coverage) for all standard methods and properties of element.prototype.classlist for ie10-ie11 browsers plus nearly compliant behavior for ie 6-9. check it out: // 1. ...
...sed to create a living classlist mockup thanks to a element.prototype.classname property that fires the specified event once it is changed. the following polyfill for both classlist and domtokenlist ensures full compliance (coverage) for all standard methods and properties of element.prototype.classlist for ie10-ie11 browsers plus nearly compliant behavior for ie 6-9. check it out: // 1. ...
...And 10 more matches

Float32Array - JavaScript
y. float32array.name returns the string value of the constructor name. in the case of the float32array type: "float32array". static methods float32array.from() creates a new float32array from an array-like or iterable object. see also array.from(). float32array.of() creates a new float32array with a variable number of arguments. see also array.of(). instance properties float32array.prototype.buffer returns the arraybuffer referenced by the float32array fixed at construction time and thus read only. float32array.prototype.bytelength returns the length (in bytes) of the float32array from the start of its arraybuffer. fixed at construction time and thus read only. float32array.prototype.byteoffset returns the offset (in bytes) of the float32array from the start of its arraybuffer. ...
...ay fixed at construction time and thus read only. float32array.prototype.bytelength returns the length (in bytes) of the float32array from the start of its arraybuffer. fixed at construction time and thus read only. float32array.prototype.byteoffset returns the offset (in bytes) of the float32array from the start of its arraybuffer. fixed at construction time and thus read only. float32array.prototype.length returns the number of elements hold in the float32array. fixed at construction time and thus read only. instance methods float32array.prototype.copywithin() copies a sequence of array elements within the array. see also array.prototype.copywithin(). float32array.prototype.entries() returns a new array iterator object that contains the key/value pairs for each index in the array. s...
...ns the number of elements hold in the float32array. fixed at construction time and thus read only. instance methods float32array.prototype.copywithin() copies a sequence of array elements within the array. see also array.prototype.copywithin(). float32array.prototype.entries() returns a new array iterator object that contains the key/value pairs for each index in the array. see also array.prototype.entries(). float32array.prototype.every() tests whether all elements in the array pass the test provided by a function. see also array.prototype.every(). ...
...And 10 more matches

Float64Array - JavaScript
y. float64array.name returns the string value of the constructor name. in the case of the float64array type: "float64array". static methods float64array.from() creates a new float64array from an array-like or iterable object. see also array.from(). float64array.of() creates a new float64array with a variable number of arguments. see also array.of(). instance properties float64array.prototype.buffer returns the arraybuffer referenced by the float64array fixed at construction time and thus read only. float64array.prototype.bytelength returns the length (in bytes) of the float64array from the start of its arraybuffer. fixed at construction time and thus read only. float64array.prototype.byteoffset returns the offset (in bytes) of the float64array from the start of its arraybuffer. ...
...ay fixed at construction time and thus read only. float64array.prototype.bytelength returns the length (in bytes) of the float64array from the start of its arraybuffer. fixed at construction time and thus read only. float64array.prototype.byteoffset returns the offset (in bytes) of the float64array from the start of its arraybuffer. fixed at construction time and thus read only. float64array.prototype.length returns the number of elements hold in the float64array. fixed at construction time and thus read only. instance methods float64array.prototype.copywithin() copies a sequence of array elements within the array. see also array.prototype.copywithin(). float64array.prototype.entries() returns a new array iterator object that contains the key/value pairs for each index in the array. s...
...ns the number of elements hold in the float64array. fixed at construction time and thus read only. instance methods float64array.prototype.copywithin() copies a sequence of array elements within the array. see also array.prototype.copywithin(). float64array.prototype.entries() returns a new array iterator object that contains the key/value pairs for each index in the array. see also array.prototype.entries(). float64array.prototype.every() tests whether all elements in the array pass the test provided by a function. see also array.prototype.every(). ...
...And 10 more matches

Int16Array - JavaScript
of an int16array. int16array.name returns the string value of the constructor name. in the case of the int16array type: "int16array". static methods int16array.from() creates a new int16array from an array-like or iterable object. see also array.from(). int16array.of() creates a new int16array with a variable number of arguments. see also array.of(). instance properties int16array.prototype.buffer returns the arraybuffer referenced by the int16array fixed at construction time and thus read only. int16array.prototype.bytelength returns the length (in bytes) of the int16array from the start of its arraybuffer. fixed at construction time and thus read only. int16array.prototype.byteoffset returns the offset (in bytes) of the int16array from the start of its arraybuffer. fixed at c...
...e int16array fixed at construction time and thus read only. int16array.prototype.bytelength returns the length (in bytes) of the int16array from the start of its arraybuffer. fixed at construction time and thus read only. int16array.prototype.byteoffset returns the offset (in bytes) of the int16array from the start of its arraybuffer. fixed at construction time and thus read only. int16array.prototype.length returns the number of elements hold in the int16array. fixed at construction time and thus read only. instance methods int16array.prototype.copywithin() copies a sequence of array elements within the array. see also array.prototype.copywithin(). int16array.prototype.entries() returns a new array iterator object that contains the key/value pairs for each index in the array. see als...
... returns the number of elements hold in the int16array. fixed at construction time and thus read only. instance methods int16array.prototype.copywithin() copies a sequence of array elements within the array. see also array.prototype.copywithin(). int16array.prototype.entries() returns a new array iterator object that contains the key/value pairs for each index in the array. see also array.prototype.entries(). int16array.prototype.every() tests whether all elements in the array pass the test provided by a function. see also array.prototype.every(). ...
...And 10 more matches

Int32Array - JavaScript
of an int32array. int32array.name returns the string value of the constructor name. in the case of the int32array type: "int32array". static methods int32array.from() creates a new int32array from an array-like or iterable object. see also array.from(). int32array.of() creates a new int32array with a variable number of arguments. see also array.of(). instance properties int32array.prototype.buffer returns the arraybuffer referenced by the int32array fixed at construction time and thus read only. int32array.prototype.bytelength returns the length (in bytes) of the int32array from the start of its arraybuffer. fixed at construction time and thus read only. int32array.prototype.byteoffset returns the offset (in bytes) of the int32array from the start of its arraybuffer. fixed at c...
...e int32array fixed at construction time and thus read only. int32array.prototype.bytelength returns the length (in bytes) of the int32array from the start of its arraybuffer. fixed at construction time and thus read only. int32array.prototype.byteoffset returns the offset (in bytes) of the int32array from the start of its arraybuffer. fixed at construction time and thus read only. int32array.prototype.length returns the number of elements hold in the int32array. fixed at construction time and thus read only. instance methods int32array.prototype.copywithin() copies a sequence of array elements within the array. see also array.prototype.copywithin(). int32array.prototype.entries() returns a new array iterator object that contains the key/value pairs for each index in the array. see als...
... returns the number of elements hold in the int32array. fixed at construction time and thus read only. instance methods int32array.prototype.copywithin() copies a sequence of array elements within the array. see also array.prototype.copywithin(). int32array.prototype.entries() returns a new array iterator object that contains the key/value pairs for each index in the array. see also array.prototype.entries(). int32array.prototype.every() tests whether all elements in the array pass the test provided by a function. see also array.prototype.every(). ...
...And 10 more matches

Int8Array - JavaScript
the case of an int8array. int8array.name returns the string value of the constructor name. in the case of the int8array type: "int8array". static methods int8array.from() creates a new int8array from an array-like or iterable object. see also array.from(). int8array.of() creates a new int8array with a variable number of arguments. see also array.of(). instance properties int8array.prototype.buffer returns the arraybuffer referenced by the int8array fixed at construction time and thus read only. int8array.prototype.bytelength returns the length (in bytes) of the int8array from the start of its arraybuffer. fixed at construction time and thus read only. int8array.prototype.byteoffset returns the offset (in bytes) of the int8array from the start of its arraybuffer. fixed at constr...
... by the int8array fixed at construction time and thus read only. int8array.prototype.bytelength returns the length (in bytes) of the int8array from the start of its arraybuffer. fixed at construction time and thus read only. int8array.prototype.byteoffset returns the offset (in bytes) of the int8array from the start of its arraybuffer. fixed at construction time and thus read only. int8array.prototype.length returns the number of elements hold in the int8array. fixed at construction time and thus read only. instance methods int8array.prototype.copywithin() copies a sequence of array elements within the array. see also array.prototype.copywithin(). int8array.prototype.entries() returns a new array iterator object that contains the key/value pairs for each index in the array. see also a...
...th returns the number of elements hold in the int8array. fixed at construction time and thus read only. instance methods int8array.prototype.copywithin() copies a sequence of array elements within the array. see also array.prototype.copywithin(). int8array.prototype.entries() returns a new array iterator object that contains the key/value pairs for each index in the array. see also array.prototype.entries(). int8array.prototype.every() tests whether all elements in the array pass the test provided by a function. see also array.prototype.every(). ...
...And 10 more matches

Uint16Array - JavaScript
nt16array. uint16array.name returns the string value of the constructor name. in the case of the uint16array type: "uint16array". static methods uint16array.from() creates a new uint16array from an array-like or iterable object. see also array.from(). uint16array.of() creates a new uint16array with a variable number of arguments. see also array.of(). instance properties uint16array.prototype.buffer returns the arraybuffer referenced by the uint16array fixed at construction time and thus read only. uint16array.prototype.bytelength returns the length (in bytes) of the uint16array from the start of its arraybuffer. fixed at construction time and thus read only. uint16array.prototype.byteoffset returns the offset (in bytes) of the uint16array from the start of its arraybuffer. fixed...
...16array fixed at construction time and thus read only. uint16array.prototype.bytelength returns the length (in bytes) of the uint16array from the start of its arraybuffer. fixed at construction time and thus read only. uint16array.prototype.byteoffset returns the offset (in bytes) of the uint16array from the start of its arraybuffer. fixed at construction time and thus read only. uint16array.prototype.length returns the number of elements hold in the uint16array. fixed at construction time and thus read only. instance methods uint16array.prototype.copywithin() copies a sequence of array elements within the array. see also array.prototype.copywithin(). uint16array.prototype.entries() returns a new array iterator object that contains the key/value pairs for each index in the array. see ...
...turns the number of elements hold in the uint16array. fixed at construction time and thus read only. instance methods uint16array.prototype.copywithin() copies a sequence of array elements within the array. see also array.prototype.copywithin(). uint16array.prototype.entries() returns a new array iterator object that contains the key/value pairs for each index in the array. see also array.prototype.entries(). uint16array.prototype.every() tests whether all elements in the array pass the test provided by a function. see also array.prototype.every(). ...
...And 10 more matches

Uint32Array - JavaScript
nt32array. uint32array.name returns the string value of the constructor name. in the case of the uint32array type: "uint32array". static methods uint32array.from() creates a new uint32array from an array-like or iterable object. see also array.from(). uint32array.of() creates a new uint32array with a variable number of arguments. see also array.of(). instance properties uint32array.prototype.buffer returns the arraybuffer referenced by the uint32array fixed at construction time and thus read only. uint32array.prototype.bytelength returns the length (in bytes) of the uint32array from the start of its arraybuffer. fixed at construction time and thus read only. uint32array.prototype.byteoffset returns the offset (in bytes) of the uint32array from the start of its arraybuffer. fixed...
...32array fixed at construction time and thus read only. uint32array.prototype.bytelength returns the length (in bytes) of the uint32array from the start of its arraybuffer. fixed at construction time and thus read only. uint32array.prototype.byteoffset returns the offset (in bytes) of the uint32array from the start of its arraybuffer. fixed at construction time and thus read only. uint32array.prototype.length returns the number of elements hold in the uint32array. fixed at construction time and thus read only. instance methods uint32array.prototype.copywithin() copies a sequence of array elements within the array. see also array.prototype.copywithin(). uint32array.prototype.entries() returns a new array iterator object that contains the key/value pairs for each index in the array. see ...
...turns the number of elements hold in the uint32array. fixed at construction time and thus read only. instance methods uint32array.prototype.copywithin() copies a sequence of array elements within the array. see also array.prototype.copywithin(). uint32array.prototype.entries() returns a new array iterator object that contains the key/value pairs for each index in the array. see also array.prototype.entries(). uint32array.prototype.every() tests whether all elements in the array pass the test provided by a function. see also array.prototype.every(). ...
...And 10 more matches

Uint8Array - JavaScript
of an uint8array. uint8array.name returns the string value of the constructor name. in the case of the uint8array type: "uint8array". static methods uint8array.from() creates a new uint8array from an array-like or iterable object. see also array.from(). uint8array.of() creates a new uint8array with a variable number of arguments. see also array.of(). instance properties uint8array.prototype.buffer returns the arraybuffer referenced by the uint8array fixed at construction time and thus read only. uint8array.prototype.bytelength returns the length (in bytes) of the uint8array. fixed at construction time and thus read only. uint8array.prototype.byteoffset returns the offset (in bytes) of the uint8array from the start of its arraybuffer. fixed at construction time and thus read onl...
...s the arraybuffer referenced by the uint8array fixed at construction time and thus read only. uint8array.prototype.bytelength returns the length (in bytes) of the uint8array. fixed at construction time and thus read only. uint8array.prototype.byteoffset returns the offset (in bytes) of the uint8array from the start of its arraybuffer. fixed at construction time and thus read only. uint8array.prototype.length returns the number of elements held in the uint8array. fixed at construction time and thus read only. instance methods uint8array.prototype.copywithin() copies a sequence of array elements within the array. see also array.prototype.copywithin(). uint8array.prototype.entries() returns a new array iterator object that contains the key/value pairs for each index in the array. see als...
... returns the number of elements held in the uint8array. fixed at construction time and thus read only. instance methods uint8array.prototype.copywithin() copies a sequence of array elements within the array. see also array.prototype.copywithin(). uint8array.prototype.entries() returns a new array iterator object that contains the key/value pairs for each index in the array. see also array.prototype.entries(). uint8array.prototype.every() tests whether all elements in the array pass the test provided by a function. see also array.prototype.every(). ...
...And 10 more matches

instanceof - JavaScript
the instanceof operator tests to see if the prototype property of a constructor appears anywhere in the prototype chain of an object. the return value is a boolean value. the source for this interactive example is stored in a github repository. if you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request. syntax object instanceof constructor parameters object the object to test. constructor function to test against description the instanceof operator tests the presence of constructor.prototype in object's prototype chain. ...
...ub.com/mdn/interactive-examples and send us a pull request. syntax object instanceof constructor parameters object the object to test. constructor function to test against description the instanceof operator tests the presence of constructor.prototype in object's prototype chain. ...
...e-examples and send us a pull request. syntax object instanceof constructor parameters object the object to test. constructor function to test against description the instanceof operator tests the presence of constructor.prototype in object's prototype chain. ...
...And 10 more matches

StringView - Archive of obsolete content
the aims of this library are: to create a c-like interface for strings (i.e., an array of character codes — an arraybufferview in javascript) based upon the javascript arraybuffer interface to create a highly extensible library that anyone can extend by adding methods to the object stringview.prototype to create a collection of methods for such string-like objects (since now: stringviews) which work strictly on arrays of numbers rather than on creating new immutable javascript strings to work with unicode encodings other than javascript's default utf-16 domstrings introduction as web applications become more and more powerful, adding features such as audio and video manipulation, access to raw data using websockets, and so forth, it has become clear that there are times when it w...
... } nuint24 = 0; } } return abytes; }; stringview.makefrombase64 = function (sb64inpt, sencoding, nbyteoffset, nlength) { return new stringview(sencoding === "utf-16" || sencoding === "utf-32" ? stringview.base64tobytes(sb64inpt, sencoding === "utf-16" ? 2 : 4).buffer : stringview.base64tobytes(sb64inpt), sencoding, nbyteoffset, nlength); }; /* default values */ stringview.prototype.encoding = "utf-8"; /* default encoding... */ /* instances' methods */ stringview.prototype.makeindex = function (nchrlength, nstartfrom) { var atarget = this.rawdata, nchrend, nrawlength = atarget.length, nstartidx = nstartfrom || 0, nidxend = nstartidx, nstopatchr = isnan(nchrlength) ? infinity : nchrlength; if (nchrlength + 1 > atarget.length) { throw new rangeerror("stringvie...
...ncoding = "utf-8"; /* default encoding... ...
...And 9 more matches

Bytecode Descriptions
rrayliteral creates a new object every time it's evaluated, so this instruction must not be used anywhere it might be executed more than once. there's a shell-only option, newglobal({clonesingletons: true}), that makes this instruction do a deep copy of the object. a few tests use it. format: jof_object objwithproto stack: proto ⇒ obj create and push a new ordinary object with the provided [[prototype]]. this is used to create the .prototype object for derived classes. defining properties initprop operands: (uint32_t nameindex) stack: obj, val ⇒ obj define a data property on an object. obj must be an object. implements: createdatapropertyorthrow as used in propertydefinitionevaluation of regular and shorthand propertydefinitions. format: jof_atom, jof_prop, jof_propinit, jof_ic inithi...
... non-enumerable property. this is used to define class methods. implements: propertydefinitionevaluation for methods, steps 3 and 4, when enumerable is false. format: jof_atom, jof_prop, jof_propinit, jof_ic initlockedprop operands: (uint32_t nameindex) stack: obj, val ⇒ obj like jsop::initprop, but define a non-enumerable, non-writable, non-configurable property. this is used to define the .prototype property on classes. implements: makeconstructor, step 8, when writableprototype is false. format: jof_atom, jof_prop, jof_propinit, jof_ic initelem, inithiddenelem stack: obj, id, val ⇒ obj define a data property on obj with property key id and value val. obj must be an object. implements: createdatapropertyorthrow. this instruction is used for object literals like {0: val} and {[id]: val},...
...eeded like jsop::delelem, but for strict mode code. pushtrue` on success, else throw a typeerror. format: jof_elem, jof_checkstrict hasown stack: id, obj ⇒ (obj.hasownproperty(id)) push true if obj has an own property id. note that obj is the top value, like jsop::in. this opcode is not used for normal js. self-hosted code uses it by calling the intrinsic hasown(id, obj). for example, object.prototype.hasownproperty is implemented this way (see js/src/builtin/object.js). format: jof_ic super superbase stack: callee ⇒ superbase push the superbase of the method callee. the superbase is callee.[[homeobject]].[[getprototypeof]](), the object where super property lookups should begin. callee must be a function that has a homeobject that's an object, typically produced by jsop::callee or jsop...
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Debugger.Object - Firefox Developer Tools
debugger.object a debugger.object instance represents an object in the debuggee, providing reflection-oriented methods to inspect and modify its referent. the referent’s properties do not appear directly as properties of the debugger.object instance; the debugger can access them only through methods like debugger.object.prototype.getownpropertydescriptor and debugger.object.prototype.defineproperty, ensuring that the debugger will not inadvertently invoke the referent’s getters and setters. spidermonkey creates exactly one debugger.object instance for each debuggee object it presents to a given debugger instance: if the debugger encounters the same object through two different routes (perhaps two functions are called on the same object), spidermonkey presents the same debugger.object instanc...
...r.object instance for a given object. this allows the code using each debugger instance to place whatever properties it likes on its own debugger.object instances, without worrying about interfering with other debuggers. while most debugger.object instances are created by spidermonkey in the process of exposing debuggee’s behavior and state to the debugger, the debugger can use debugger.object.prototype.makedebuggeevalue to create debugger.object instances for given debuggee objects, or use debugger.object.prototype.copy and debugger.object.prototype.create to create new objects in debuggee compartments, allocated as if by particular debuggee globals. debugger.object instances protect their referents from the garbage collector; as long as the debugger.object instance is live, the referent remai...
...this accessor may throw if the referent is a scripted proxy or some other sort of exotic object (an opaque wrapper, for example). class a string naming the ecmascript [[class]] of the referent. ...
...And 9 more matches

Debugger.Object - Firefox Developer Tools
debugger.object a debugger.object instance represents an object in the debuggee, providing reflection-oriented methods to inspect and modify its referent. the referent's properties do not appear directly as properties of the debugger.object instance; the debugger can access them only through methods like debugger.object.prototype.getownpropertydescriptor and debugger.object.prototype.defineproperty, ensuring that the debugger will not inadvertently invoke the referent's getters and setters. spidermonkey creates exactly one debugger.object instance for each debuggee object it presents to a given debugger instance: if the debugger encounters the same object through two different routes (perhaps two functions are called on the same object), spidermonkey presents the same debugger.object instance to...
...ger.object instance for a given object. this allows the code using each debugger instance to place whatever properties it likes on its own debugger.object instances, without worrying about interfering with other debuggers. while most debugger.object instances are created by spidermonkey in the process of exposing debuggee's behavior and state to the debugger, the debugger can use debugger.object.prototype.makedebuggeevalue to create debugger.object instances for given debuggee objects, or use debugger.object.prototype.copy and debugger.object.prototype.create to create new objects in debuggee compartments, allocated as if by particular debuggee globals. debugger.object instances protect their referents from the garbage collector; as long as the debugger.object instance is live, the referent remai...
... class a string naming the ecmascript [[class]] of the referent. callable true if the referent is a callable object (such as a function or a function proxy); false otherwise. ...
...And 9 more matches

Index - Web APIs
488 cssunparsedvalue.foreach() api, css typed object model api, cssunparsedvalue, constructor, experimental, houdini, method, needsexample, reference, foreach() the cssunparsedvalue.foreach() method executes a provided function once for each element of the cssunparsedvalue. 489 cssunparsedvalue.keys() api, css typed object model api, cssunparsed...
... 2225 keyboardlayoutmap.foreach() api, experimental, keyboard api, keyboard map, keyboardlayoutmap, method, reference, foreach(), keyboard the foreach() method of the keyboardlayoutmap interface executes a provided function once for each element of the map. 2226 keyboardlayoutmap.get() api, experimental, keyboard api, keyboard map, keyboardlayou...
...s() dom, iterator, method, nodelist, reference, web the nodelist.keys() method returns an iterator allowing to go through all keys contained in this object. the keys are unsigned integer. 2755 nodelist.length api, dom, gecko, needsspectable, nodelist, property, reference the nodelist.length property returns the number of items in a nodelist. 2756 nodelist.prototype.foreach() dom, iterable, method, nodelist, reference, web the foreach() method of the nodelist interface calls the callback given in parameter once for each value pair in the list, in insertion order. 2757 nodelist.values() dom, iterator, method, nodelist, reference, web the nodelist.values() method returns an iterator allowing to go through all values contained in ...
...And 9 more matches

WindowOrWorkerGlobalScope.setInterval() - Web APIs
return false; } } amap.length--; return true; } function typewrite () { if (spart.length === 0 && scroll(asheets[nidx], 0, true) && nidx++ === asheets.length - 1) { clean(); return; } ocurrent.nodevalue += spart.charat(0); spart = spart.slice(1); } function sheet (onode) { this.ref = onode; if (!onode.haschildnodes()) { return; } this.parts = array.prototype.slice.call(onode.childnodes); for (var nchild = 0; nchild < this.parts.length; nchild++) { onode.removechild(this.parts[nchild]); this.parts[nchild] = new sheet(this.parts[nchild]); } } var nintervid, ocurrent = null, btyping = false, bstart = true, nidx = 0, spart = "", asheets = [], amap = []; this.rate = nrate || 100; this.play = function () { if (bt...
...var timeoutid = window.settimeout(code, delay); |*| var intervalid = window.setinterval(func, delay[, arg1, arg2, ...]); |*| var intervalid = window.setinterval(code, delay); |*| \*/ if (document.all && !window.settimeout.ispolyfill) { var __nativest__ = window.settimeout; window.settimeout = function (vcallback, ndelay /*, argumenttopass1, argumenttopass2, etc. */) { var aargs = array.prototype.slice.call(arguments, 2); return __nativest__(vcallback instanceof function ? function () { vcallback.apply(null, aargs); } : vcallback, ndelay); }; window.settimeout.ispolyfill = true; } if (document.all && !window.setinterval.ispolyfill) { var __nativesi__ = window.setinterval; window.setinterval = function (vcallback, ndelay /*, argumenttopass1, argumenttopass2, etc. */)...
...; return __nativest__(vcallback instanceof function ? function () { vcallback.apply(null, aargs); } : vcallback, ndelay); }; window.settimeout.ispolyfill = true; } if (document.all && !window.setinterval.ispolyfill) { var __nativesi__ = window.setinterval; window.setinterval = function (vcallback, ndelay /*, argumenttopass1, argumenttopass2, etc. */) { var aargs = array.prototype.slice.call(arguments, 2); return __nativesi__(vcallback instanceof function ? function () { vcallback.apply(null, aargs); } : vcallback, ndelay); }; window.setinterval.ispolyfill = true; } another possibility is to use an anonymous function to call your callback, although this solution is a bit more expensive. example: var intervalid = setinterval(function() { myfunc('one', '...
...And 9 more matches

TypeError: "x" is not a function - JavaScript
function name? maybe the object you are calling the method on does not have this function? for example, javascript objects have no map function, but the javascript array object does. there are many built-in functions in need of a (callback) function. ...
... object you are calling the method on does not have this function? for example, javascript objects have no map function, but the javascript array object does. there are many built-in functions in need of a (callback) function. ...
...the method on does not have this function? for example, javascript objects have no map function, but the javascript array object does. there are many built-in functions in need of a (callback) function. ...
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Old Proxy API - Archive of obsolete content
non-standard this feature is non-standard and is not on a standards track. do not use it on production sites facing the web: it will not work for every user. there may also be large incompatibilities between implementations and the behavior may change in the future. warning: the spidermonkey proxy implementation is a prototype and the proxy api and semantics specifications are unstable. the spidermonkey implementation may not reflect the latest specification draft. it is subject to change anytime. it is provided as an experimental feature. do not rely on it for production code. introduction proxies are objects for which the programmer has to define the semantics in javascript. the default object semantics are implemented in the javascript engine, often written...
.... proxies can be either be trapping or fixed. proxy api catch-alls can be defined only on distinct proxy objects, controlled by a handler object. there are two kinds of proxies: object proxies var proxy = proxy.create(handler, proto); and function proxies : var proxy = proxy.createfunction(handler, calltrap, constructtrap); where: proto is an optional object representing the proxy’s prototype (defaults to null if none is provided). calltrap is a variable-argument function(args) { return any; } that reifies “proxy(args)”. note: the this-binding of the calltrap function is the this-binding of the call-site. constructtrap is an optional variable-argument function(args) { return any-object; } that reifies “new proxy(args)”. the this-binding of the constructtrap is either undefin...
...all-site. constructtrap is an optional variable-argument function(args) { return any-object; } that reifies “new proxy(args)”. the this-binding of the constructtrap is either undefined (in strict mode) or the global object (in non-strict mode). if no constructtrap is provided, performing new proxy(...args) calls the proxy’s calltrap with this bound to a new object delegating to the proxy's prototype. handler is an object that implements the handler api. handler api there are two kinds of traps: fundamental and derived traps. if one of the fundamental traps isn't implemented and the proxy is used in a way that expects the fundamental trap to be defined, then an error is thrown. if a derived trap is implemented, then that trap's code is called whenever the corresponding behavior happens on...
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JS_InitClass
syntax jsobject * js_initclass(jscontext *cx, js::handleobject obj, js::handleobject parent_proto, const jsclass *clasp, jsnative constructor, unsigned nargs, const jspropertyspec *ps, const jsfunctionspec *fs, const jspropertyspec *static_ps, const jsfunctionspec *static_fs); name type description cx jscontext * pointer to a js context from which to derive runtime information. requires request. in a js_threadsafe build, the caller must be in a request on this jscontext. ...
..."globals" object to use for initializing the class. this must not be null. once js_initclass creates the new class's constructor, it stores the constructor as a property in this object. so, for example, if this object is js_getglobalobject(cx), then javascript code will be able to see the new class as a global name. parent_proto js::handleobject pointer to an object to be used as a prototype. js_initclass always creates a new prototype object that serves as the __proto__ for class instances; parent_proto becomes the __proto__ of that prototype object. clasp jsclass * pointer to the class structure to initialize. this structure defines the class for use by other api functions. constructor jsnative the constructor for the class. its scope matches that...
...l js_this or js_this_object. instead it must create a new object and return it. nargs unsigned number of arguments for the constructor. ps jspropertyspec * either null or a pointer to the first element of an array of jspropertyspecs, terminated by the null jspropertyspec, which can be written {0, 0, 0, 0, 0}. these properties, if any, are added to the class's new prototype object. all instances of the new class will inherit these properties via the prototype chain. fs jsfunctionspec * either null or a pointer to the first element of an array of jsfunctionspecs, terminated by js_fs_end. these functions, if any, are added to the class's new prototype object. all instances of the new class will inherit these methods via the prototype chain. (this is the...
...And 8 more matches

Xray vision
code. most of the time this is not a problem: the main concern xrays solve is with untrusted web content manipulating objects, and web content is usually working with dom objects. ...
.... so, in gecko 31 and 32 we've added xray support for most javascript built-in objects. ...
... it easy for privileged code to treat untrusted objects like simple dictionaries. any value properties of the object are visible in the xray. if the object has properties which are themselves objects, and these objects are same-origin with the content, then their value properties are visible as well. ...
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JXON - Archive of obsolete content
) { oattrib = oxmlparent.attributes.item(nattrlen); this.keyattributes[oattrib.name.tolowercase()] = parsetext(oattrib.value.trim()); } } /* * optional properties... this.keylength = nlength; this.attributeslength = nattrlen; // this.domnode = oxmlparent; */ /* object.freeze(this); */ } /* * optional methods... ...
....keyattributes[oattrib.name.tolowercase()] = parsetext(oattrib.value.trim()); } } /* * optional properties... this.keylength = nlength; this.attributeslength = nattrlen; // this.domnode = oxmlparent; */ /* object.freeze(this); */ } /* * optional methods... ...
... } } /* * optional properties... this.keylength = nlength; this.attributeslength = nattrlen; // this.domnode = oxmlparent; */ /* object.freeze(this); */ } /* * optional methods... ...
...And 7 more matches

Meta programming - JavaScript
s that remain unchanged when implementing custom operations are called invariants. if you violate the invariants of a handler, a typeerror will be thrown. handlers and traps the following table summarizes the available traps available to proxy objects. see the reference pages for detailed explanations and examples. ...
...n implementing custom operations are called invariants. if you violate the invariants of a handler, a typeerror will be thrown. handlers and traps the following table summarizes the available traps available to proxy objects. see the reference pages for detailed explanations and examples. ...
...ons are called invariants. if you violate the invariants of a handler, a typeerror will be thrown. handlers and traps the following table summarizes the available traps available to proxy objects. see the reference pages for detailed explanations and examples. ...
...And 7 more matches

Working with objects - JavaScript
with for...in to iterate over all the enumerable properties of an object. ...
... object.getownpropertynames(o) this method returns an array containing all own properties' names (enumerable or not) of an object o. before ecmascript 5, there was no native way to list all properties of an object. however, this can be achie...
...ould return the following: mycar.make = ford mycar.model = mustang mycar.year = 1969 enumerate the properties of an object starting with ecmascript 5, there are three native ways to list/traverse object properties: for...in loops this method traverses all enumerable properties of an object and its prototype chain. object.keys(o) this method returns an array with all the own (not in the prototype chain) enumerable properties' names ("keys") of an object o. object.getownpropertynames(o) this method returns an array containing all own properties' names (enumerable or not) of an object o. before ecmascript 5, there was no native way to list all properties of an object. however, this can be achieved with the following function: function listallproperties(o) { var objecttoinspect; var ...
...And 7 more matches

Classes - JavaScript
defining classes classes are in fact "special functions", and just as you can define function expressions and function declarations, the class syntax has two components: class expressions and class declarations. class declarations one way to define a class is using a class declaration. to declare a class, you use the class keyword with the name of the class ("rectangle" here). ...
...s of ecmascript. constructor the constructor method is a special method for creating and initializing an object created with a class. there can only be one special method with the name "constructor" in a class. a syntaxerror will be thrown if the class contains more than one occurrence of a constructor method. a constructor can use the super keyword to call the constructor of the super class. prototype methods see also method definitions. class rectangle { constructor(height, width) { this.height = height; this.width = width; } // getter get area() { return this.calcarea(); } // method calcarea() { return this.height * this.width; } } const square = new rectangle(10, 10); console.log(square.area); // 100 static methods the static keyword defines a static me...
... for an application. class point { constructor(x, y) { this.x = x; this.y = y; } static distance(a, b) { const dx = a.x - b.x; const dy = a.y - b.y; return math.hypot(dx, dy); } } const p1 = new point(5, 5); const p2 = new point(10, 10); p1.distance; //undefined p2.distance; //undefined console.log(point.distance(p1, p2)); // 7.0710678118654755 binding this with prototype and static methods when a static or prototype method is called without a value for this, such as by assigning a variable to the method and then calling it, the this value will be undefined inside the method. this behavior will be the same even if the "use strict" directive isn't present, because code within the class body's syntactic boundary is always executed in strict mode. class animal { ...
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DataView - JavaScript
4-byte) parts const left = bigint(dataview.getuint32(byteoffset|0, !!littleendian)>>>0); const right = bigint(dataview.getuint32((byteoffset|0) + 4|0, !!littleendian)>>>0); // combine the two 32-bit values and return return littleendian ? (right<<bigthirtytwo)|left : (left<<bigthirtytwo)|right; } constructor dataview() creates a new dataview object. instance properties dataview.prototype.buffer the arraybuffer referenced by this view. fixed at construction time and thus read only. dataview.prototype.bytelength the length (in bytes) of this view from the start of its arraybuffer. fixed at construction time and thus read only. dataview.prototype.byteoffset the offset (in bytes) of this view from the start of its arraybuffer. fixed at construction time and thus read only. ins...
...eferenced by this view. fixed at construction time and thus read only. dataview.prototype.bytelength the length (in bytes) of this view from the start of its arraybuffer. fixed at construction time and thus read only. dataview.prototype.byteoffset the offset (in bytes) of this view from the start of its arraybuffer. fixed at construction time and thus read only. instance methods dataview.prototype.getint8() gets a signed 8-bit integer (byte) at the specified byte offset from the start of the view. dataview.prototype.getuint8() gets an unsigned 8-bit integer (unsigned byte) at the specified byte offset from the start of the view. ...
...set (in bytes) of this view from the start of its arraybuffer. fixed at construction time and thus read only. instance methods dataview.prototype.getint8() gets a signed 8-bit integer (byte) at the specified byte offset from the start of the view. dataview.prototype.getuint8() gets an unsigned 8-bit integer (unsigned byte) at the specified byte offset from the start of the view. dataview.prototype.getint16() gets a signed 16-bit integer (short) at the specified byte offset from the start of the view. dataview.prototype.getuint16() gets an unsigned 16-bit integer (unsigned short) at the specified byte offset from the start of the view. ...
...And 7 more matches

Error - JavaScript
ccurs when a variable or parameter is not of a valid type. urierror creates an instance representing an error that occurs when encodeuri() or decodeuri() are passed invalid parameters. constructor error() creates a new error object. static methods error.capturestacktrace() a non-standard v8 function that creates the stack property on an error instance. ...
... of a valid type. urierror creates an instance representing an error that occurs when encodeuri() or decodeuri() are passed invalid parameters. constructor error() creates a new error object. static methods error.capturestacktrace() a non-standard v8 function that creates the stack property on an error instance. instance properties error.prototype.message error message. error.prototype.name error name. ...
...s an instance representing an error that occurs when encodeuri() or decodeuri() are passed invalid parameters. constructor error() creates a new error object. static methods error.capturestacktrace() a non-standard v8 function that creates the stack property on an error instance. instance properties error.prototype.message error message. error.prototype.name error name. error.prototype.description a non-standard microsoft property for the error description. similar to message. error.prototype.number a non-standard microsoft property for an error number. error.prototype.filename a non-standard mozilla property for the path to the file that raised this error. error.prototype.linenumber a non-standard mozilla property for the line number in the file that raised this error. ...
...And 7 more matches

Index - Archive of obsolete content
r, experimental, javascript, method, reference, typedarrays the static arraybuffer.transfer() method returns a new arraybuffer whose contents have been taken from the oldbuffer's data and then is either truncated or zero-extended by newbytelength. if newbytelength is undefined, the bytelength of the oldbuffer is used. this operation leaves oldbuffer in a detached state. 2008 date.prototype.tolocaleformat() date, javascript, method, non-standard, prototype, reference the non-standard tolocaleformat() method converts a date to a string using the specified formatting. intl.datetimeformat is an alternative to format dates in a standards-compliant way. see also the newer version of date.prototype.tolocaledatestring(). 2009 ecmascript 2016 to es.next support in mozil...
...vascript, needsupdate no summary! 2010 expression closures function, javascript, language feature, non-standard, obsolete, operator, reference expression closures are a shorthand function syntax for writing simple functions. 2011 function.arity function, javascript, obsolete, property, unimplemented not part of any standard. 2012 function.prototype.isgenerator() function, javascript, method, non-standard, obsolete the non-standard isgenerator() method used to determine whether or not a function is a generator. it has been removed from firefox starting with version 58. 2013 generator comprehensions iterator, javascript, language feature, non-standard, obsolete, reference the generator comprehension syntax was a...
...d removed in browsers. 2066 object.observe() javascript, method, object, obsolete the object.observe() method was used for asynchronously observing the changes to an object. it provided a stream of changes in the order in which they occur. however, this api has been deprecated and removed from browsers. you can use the more general proxy object instead. ...
...And 6 more matches

Element.matches() - Web APIs
nsole.log('the ' + birds[i].textcontent + ' is endangered!'); } } </script> this will log "the philippine eagle is endangered!" to the console, since the element has indeed a class attribute with value endangered. ...
...tcontent + ' is endangered!'); } } </script> this will log "the philippine eagle is endangered!" to the console, since the element has indeed a class attribute with value endangered. ...
... } } </script> this will log "the philippine eagle is endangered!" to the console, since the element has indeed a class attribute with value endangered. ...
...And 6 more matches

Border-radius generator - CSS: Cascading Style Sheets
pic) { this.container = document.createelement("div"); this.select = document.createelement("select"); for (var i in units) { var option = document.createelement("option"); option.value = i; option.textcontent = units[i]; this.select.appendchild(option); } this.container.classname = 'dropdown ' + 'unit-' + topic; this.container.appendchild(this.select); } unitselector.prototype.setvalue = function setvalue(value) { this.salect.value = value; } var radiuscontainer = function radiuscontainer(node) { var radius = document.createelement('div'); var handle = document.createelement('div'); var x = node.getattribute('data-x'); var y = node.getattribute('data-y'); var active = false; this.id = node.id; this.node = node; this.radius = radius; this.handle...
...iner.style.display = 'block'; unitr.container.style.display = 'none'; sliderw.style.display = 'block'; sliderh.style.display = 'block'; sliderr.style.display = 'none'; this.setunitx(this.unitx); this.setunity(this.unity); this.updatewidth(); this.updateheight(); } this.updateborderradius(); }.bind(this)); this.updateborderradius(); } radiuscontainer.prototype.updatewidth = function updatewidth() { this.node.style.width = this.width + units[this.unitx]; var value = math.round(this.width / 2); inputslidermanager.setvalue(this.topic + '-w', value, false); } radiuscontainer.prototype.updateheight = function updateheight() { this.node.style.height = this.height + units[this.unity]; var value = math.round(this.height / 2); inputslidermanager.
...= this.width + units[this.unitx]; var value = math.round(this.width / 2); inputslidermanager.setvalue(this.topic + '-w', value, false); } radiuscontainer.prototype.updateheight = function updateheight() { this.node.style.height = this.height + units[this.unity]; var value = math.round(this.height / 2); inputslidermanager.setvalue(this.topic + '-h', value, false); } radiuscontainer.prototype.updateradius = function updateradius() { var value = math.round(this.size / 2); this.node.style.width = this.size + units[this.unitr]; this.node.style.height = this.size + units[this.unitr]; inputslidermanager.setvalue(this.topic, value, false); } radiuscontainer.prototype.setwidth = function setwidth(value) { this.radius.style.display = 'block'; this.width = 2 * value; this.node...
...And 6 more matches

JavaScript Client API - Archive of obsolete content
xt. cleartext must be a json-able object. put into it all values that you want to have encrypted, stored on the server, decrypted, and synced up. you may find it useful to write getters and setters for various properties of your record implementation. ...
... put into it all values that you want to have encrypted, stored on the server, decrypted, and synced up. you may find it useful to write getters and setters for various properties of your record implementation. ...
... the store must also make updates to the underl...
...And 5 more matches

Archived JavaScript Reference - Archive of obsolete content
browsers. you can use the more general proxy object instead.arraybuffer.transfer()the static arraybuffer.transfer() method returns a new arraybuffer whose contents have been taken from the oldbuffer's data and then is either truncated or zero-extended by newbytelength. if newbytelength is undefined, the bytelength of the oldbuffer is used. ...
...tended by newbytelength. if newbytelength is undefined, the bytelength of the oldbuffer is used. this operation leaves oldbuffer in a detached state.date.prototype.tolocaleformat()the non-standard tolocaleformat() method converts a date to a string using the specified formatting. intl.datetimeformat is an alternative to format dates in a standards-compliant way. ...
...it has been removed from firefox starting with version 58.generator comprehensionsthe generator comprehension syntax was a javascript expression which allowed you to quickly assemble a new generator function based on an existing iterable object. ...
...And 5 more matches

NSS functions
reference documents the functions most commonly used by applications to support ssl. the nss home page links to additional ssl documentation. if documentation is available for a function listed below, the function name is linked to either its mdc wiki page or its entry in the old ssl reference. the mozilla cross reference (mxr) link for each function provides access to the function definition, prototype definition, and source code references. the nss version column indicates which versions of nss support the function. function name/documentation source code nss versions nss_getclientauthdata mxr 3.2 and later nss_setdomesticpolicy mxr 3.2 and later nss_setexportpolicy mxr 3.2 and later nss_setfrancepolicy mxr 3.2 and l...
...n replaced with newer versions. the deprecated functions are not supported by the new ssl shared libraries. applications that want to use the ssl shared libraries must convert to calling the new replacement functions listed below. each function name is linked to its entry in the old ssl reference. the mozilla cross reference (mxr) link for each function provides access to the function definition, prototype definition, and source code references. function name/documentation source code replacement in nss 3.2 ssl_enable mxr ssl_optionset ssl_enablecipher mxr ssl_cipherprefsetdefault ssl_enabledefault mxr ssl_optionsetdefault ssl_redohandshake mxr ssl_rehandshake ...
...r ssl_cipherpolicyset certificate functions the public functions listed here are used to interact with certificate databases. if documentation is available for a function listed below, the function name is linked to either its mdc wiki page or its entry in the old ssl reference. the mozilla cross reference (mxr) link for each function provides access to the function definition, prototype definition, and source code references. the nss version column indicates which versions of nss support the function. function name/documentation source code nss versions cert_addcerttolisttail mxr 3.2 and later cert_addextension mxr 3.5 and later cert_addocspacceptableresponses mxr 3.6 and later cert_addokdomainname mxr 3.
...And 5 more matches

EventTarget.addEventListener() - Web APIs
ndard rules. this is shown in the following example: <script> function logid() { console.log(this.id); } </script> <table id="my_table" onclick="logid();"><!-- when called, `this` will refer to the global object --> ... </table> the value of this within logid() is a reference to the global object window (or undefined in the case of strict mode. specifying "this" using bind() the function.prototype.bind() method lets you specify the value that should be used as this for all calls to a given function. this lets you easily bypass problems where it's unclear what this will be, depending on the context from which your function was called. note, however, that you'll need to keep a reference to the listener around so you can remove it later. this is an example with and without bind(): const som...
...ta, much less to get any data back from them after they execute. event listeners only take one argument, the event object, which is automatically passed to the listener, and the return value is ignored. so how can we get data in and back out of them again? there are a number of good methods for doing this. getting data into an event listener using "this" as mentioned above, you can use function.prototype.bind() to pass a value to an event listener via the this reference variable. const mybutton = document.getelementbyid('my-button-id'); const somestring = 'data'; mybutton.addeventlistener('click', function () { console.log(this); // expected value: 'data' }.bind(somestring)); this method is suitable when you don't need to know which html element the event listener fired on programmatically...
...internet explorer 8 by using the following code at the beginning of your script. the code supports the use of handleevent() and also the domcontentloaded event. note: usecapture is not supported, as ie 8 does not have any alternative method. the following code only adds ie 8 support. this ie 8 polyfill only works in standards mode: a doctype declaration is required. ...
...And 5 more matches

RegExp - JavaScript
e value. (perl is the programming language from which javascript modeled its regular expressions.). see also deprecated regexp properties. constructor regexp() creates a new regexp object. static properties get regexp[@@species] the constructor function that is used to create derived objects. regexp.lastindex the index at which to start the next match. ...
...ular expressions.). see also deprecated regexp properties. constructor regexp() creates a new regexp object. static properties get regexp[@@species] the constructor function that is used to create derived objects. regexp.lastindex the index at which to start the next match. instance properties regexp.prototype.flags a string that contains the flags of the regexp object. regexp.prototype.dotall whether . matches newlines or not. ...
...onstructor regexp() creates a new regexp object. static properties get regexp[@@species] the constructor function that is used to create derived objects. regexp.lastindex the index at which to start the next match. instance properties regexp.prototype.flags a string that contains the flags of the regexp object. regexp.prototype.dotall whether . matches newlines or not. regexp.prototype.global whether to test the regular expression against all possible matches in a string, or only against the first. ...
...And 5 more matches

New in JavaScript 1.2 - Archive of obsolete content
. --> <script language="javascript1.2"> <!-- javascript for navigator 4.0. --> new features in javascript 1.2 new objects you can create objects using literal notation (inspired by dictionary literal syntax from python 1.x). arrays can now be created using literal notation (inspired by list literal syntax from python 1.x). ...
...vascript1.2"> <!-- javascript for navigator 4.0. --> new features in javascript 1.2 new objects you can create objects using literal notation (inspired by dictionary literal syntax from python 1.x). arrays can now be created using literal notation (inspired by list literal syntax from python 1.x). ...
...ipt for navigator 4.0. --> new features in javascript 1.2 new objects you can create objects using literal notation (inspired by dictionary literal syntax from python 1.x). arrays can now be created using literal notation (inspired by list literal syntax from python 1.x). ...
...And 4 more matches

Log.jsm
to a minimum. config information regarding important configuration options the system is using that affect how it runs. debug detailed information on the flow through the system. expect these to be written to logs only. trace most detailed information. expect these to be written to logs only. ...
... through the system. expect these to be written to logs only. trace most detailed information. expect these to be written to logs only. ...
... written to logs only. ...
...And 4 more matches

SourceMap.jsm
lowing. sources: an array of urls to the original source files. names: an array of identifiers that can be referenced by individual mappings. sourceroot: optional. the url root from which all sources are relative. mappings: a string of base64 vlqs which contain the actual mappings. file: the generated filename this source map is associated with. sourcemapconsumer.prototype.originalpositionfor(generatedposition) returns the original source, line, and column information for the generated source's line and column positions provided. the only argument is an object with the following properties: line: the line number in the generated source. column: the column number in the generated source. and an object is returned with the following properties: ...
...ance of the sourcemapgenerator represents a source map which is being built incrementally. new sourcemapgenerator(startofsourcemap) to create a new one, you must pass an object with the following properties: file: the filename of the generated source that this source map is associated with. sourceroot: an optional root for all relative urls in this source map. sourcemapgenerator.prototype.addmapping(mapping) add a single mapping from original source line and column to the generated source's line and column for this source map being created. the mapping object should have the following properties: generated: an object with the generated line and column positions. original: an object with the original line and column positions. source: the original source file (re...
...nd column for this source map being created. the mapping object should have the following properties: generated: an object with the generated line and column positions. original: an object with the original line and column positions. source: the original source file (relative to the sourceroot). name: an optional original token name for this mapping. sourcemapgenerator.prototype.tostring() renders the source map being generated to a string. sourcenode sourcenodes provide a way to abstract over interpolating and/or concatenating snippets of generated javascript source code, while maintaining the line and column information associated between those snippets and the original source code. this is useful as the final intermediate representation a compiler might use before ...
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Enumerability and ownership of properties - JavaScript
le flag is set to true, which is the default for properties created via simple assignment or via a property initializer (properties defined via object.defineproperty and such default enumerable to false). enumerable properties show up in for...in loops unless the property's key is a symbol. ownership of properties is determined by whether the property belongs to the object directly and not to its prototype chain. properties of an object can also be retrieved in total. there are a number of built-in means of detecting, iterating/enumerating, and retrieving object properties, with the chart showing below which are available. some sample code follows which demonstrates how to obtain the missing categories. property enumerability and ownership - built-in methods of detection, retrieval, and iterati...
...l. there are a number of built-in means of detecting, iterating/enumerating, and retrieving object properties, with the chart showing below which are available. some sample code follows which demonstrates how to obtain the missing categories. ...
...er of built-in means of detecting, iterating/enumerating, and retrieving object properties, with the chart showing below which are available. some sample code follows which demonstrates how to obtain the missing categories. ...
...And 4 more matches

TypeError: Reduce of empty array with no initial value - JavaScript
these functions optionally take an initialvalue (which will be used as the first argument to the first call of the callback). ...
... these functions optionally take an initialvalue (which will be used as the first argument to the first call of the callback). ...
... these functions optionally take an initialvalue (which will be used as the first argument to the first call of the callback). ...
...And 4 more matches

Map - JavaScript
thing is stored at a key. for this reason (and because there were no built-in alternatives), objects have been used as maps historically. however, there are important differences that make map preferable in certain cases: map object accidental keys a map does not contain any keys by default. it only contains what is explicitly put into it. an object has a prototype, so it contains default keys that could collide with your own keys if you're not careful. note: as of es5, this can be bypassed by using object.create(null), but this is seldom done. key types a map's keys can be any value (including functions, objects, or any primitive). the keys of an object must be either a string or a symbol. key order the ke...
...-4321", address: "321 s 2nd st"}) contacts.get('jessie') // {phone: "213-555-1234", address: "123 n 1st ave"} contacts.delete('raymond') // false contacts.delete('jessie') // true console.log(contacts.size) // 1 constructor map() creates a new map object. static properties get map[@@species] the constructor function that is used to create derived objects. ...
... 1st ave"} contacts.delete('raymond') // false contacts.delete('jessie') // true console.log(contacts.size) // 1 constructor map() creates a new map object. static properties get map[@@species] the constructor function that is used to create derived objects. instance properties map.prototype.size returns the number of key/value pairs in the map object. instance methods map.prototype.clear() removes all key-value pairs from the map object. ...
...And 4 more matches

Object initializer - JavaScript
3 let param = 'size' let config = { [param]: 12, ['mobile' + param.charat(0).touppercase() + param.slice(1)]: 4 } console.log(config) // {size: 12, mobilesize: 4} spread properties the rest/spread properties for ecmascript proposal (stage 4) adds spread properties to object literals. it copies own enumerable properties from a provided object onto a new object. ...
...cloning (excluding prototype) or merging objects is now possible using a shorter syntax than object.assign(). let obj1 = { foo: 'bar', x: 42 } let obj2 = { foo: 'baz', y: 13 } let clonedobj = { ...obj1 } // object { foo: "bar", x: 42 } let mergedobj = { ...obj1, ...obj2 } // object { foo: "baz", x: 42, y: 13 } note that object.assign() triggers setters, whereas the spread operator doesn't! ...
...{ foo: "bar", x: 42 } let mergedobj = { ...obj1, ...obj2 } // object { foo: "baz", x: 42, y: 13 } note that object.assign() triggers setters, whereas the spread operator doesn't! ...
...And 4 more matches

Reference - Archive of obsolete content
its constructor note : the function.constructor seems to keep on refering to itself, if you do the following you get same results which suggests that this is indeed the top level object. alert(function.constructor.constructor) alert(function.constructor.constructor.constructor.constructor) function == object however the following statement suggests that function is object. ...
...efering to itself, if you do the following you get same results which suggests that this is indeed the top level object. alert(function.constructor.constructor) alert(function.constructor.constructor.constructor.constructor) function == object however the following statement suggests that function is object. ...
....constructor.constructor.constructor) function == object however the following statement suggests that function is object. but when we create a prototype method for object its also available in function object.prototype.myfunction = function() {}; alert(object.myfunction); //available in object alert(function.myfunction); //available in function also the opposite is correct, when we create a prototype method for function it is available in object function.prototype.myfunction = function() {}; alert(object.myfunction); //available in object alert(function.myfunction); //available in function so no matter what we prototype function or object , it will be available in both... <p>so all this now suggests that function is object. note that instances derived from function/object also have this f...
...And 3 more matches

Mozilla DOM Hacking Guide
p me! static prbool sdosecuritycheckinaddproperty;: help me! nsdomclassinfo::init() this method is to be called only once. its purpose is, well, to initialize... it does a lot of different things: fill the blanks in the sclassinfodata array, initialize the sxpconnect and ssecman data members, create a new javascript context, define the jsstring data members, and register class names and class prototypes. finally it sets sisinitialized to true. the actions that concern the dom are described below. first, the call to callgetservice() initializes sxpconnect. then the script security manager (ssecman) is initialized. getsafejscontext() grabs us a cool js context to run our javascript code in. the part about componentregistrar is designed to allow external modules (in this case xpath) to be include...
...interface, yet you want the xmlhttprequest object to be available from javascript. #define dom_classinfo_map_begin_no_class_if(_class, _interface) _dom_classinfo_map_begin(_class, &ns_get_iid(_interface), pr_false) this macro should be used for dom classes that have no "leaf" interface. for example, there is no htmlspanelement in the w3c dom specification. therefore, the first interface in the prototype chain for the span element is htmlelement. however we do want to be able to access htmlspanelement to modify it. this macro allows you to do that. see bug 92071 for more information. let's now see how to specify the interfaces available from javascript for a particular dom class. #define dom_classinfo_map_entry(_if) &ns_get_iid(_if), the array of pointers interface_list is filled with the addr...
... now possible. i will try to update this guide as soon as possible. please send any comment to fabian guisset. ...
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JS_NewObject
must not have the jsclass_global_flags bits set (use js_newglobalobject instead). if clasp is non-null, the caller must ensure that the jsclass remains alive throughout the lifetime of the new object, including the garbage collection cycle that finally frees it. the usual way to do this is to make jsclasses global or static. proto js::handle&lt;jsobject*&gt; pointer to the prototype object to use for the new object. the new object will inherit all of the prototype object's properties and methods, and the new object's __proto__ property will be a reference to the prototype object. js_newobject: if this is null, a default prototype object is used. obsolete since jsapi 38 js_newobject now always uses a default prototype object. js_newobjectwithgivenproto: if this...
... parent js::handle&lt;jsobject*&gt; pointer to the parent of the new object. the new object's __parent__ property will be a reference to this object. if parent is null, a default parent object is used. ...
...a reference to this object. if parent is null, a default parent object is used. obsolete since jsapi 39 description js_newobject creates a new object based on a specified class. cx is a pointer to a context associated with the runtime in which to establish the new object. clasp is a pointer to an existing class to use for internal methods, such as finalize. the javascript engine selects a prototype object for you. on success, js_newobject returns a pointer to the new object. otherwise it returns null. added in spidermonkey 1.8 js_newobjectwithgivenproto creates a new object with the specified prototype. if null is passed as proto, the new object will have a prototype with the js value of null. to create a new object as a property of an existing object, use js_defineobject, a convenience ...
...And 3 more matches

nsIXPConnect
obsolete since gecko 2.0 jsval getxowforobject(in jscontextptr ajscontext, in jsobjectptr aparent, in jsobjectptr awrap...
...sholder(in voidptr aholder); native code only! void reparentscopeawarewrappers(in jscontextptr ajscontext, in jsobjectptr aoldscope, in jsobjectptr anewscope); obsolete since gecko 1.9.1 nsixpconnectjsobjectholder reparentwrappednativeiffound(in jscontextptr ajscontext, in jsobjectptr ascope, in jsobjectptr anewparent, in nsisupports acomobj); void restorewrappednativeprototype(in jscontextptr ajscontext, in jsobjectptr ascope, in nsiclassinfo aclassinfo, in nsixpconnectjsobjectholder aprototype); void setdebugmodewhenpossible(in prbool mode); native code only! void setdefaultsecuritymanager(in nsixpcsecuritymanager amanager, in pruint16 flags); nsixpcfunctionthistranslator setfunctionthistranslator(in nsiidref aiid, in nsixpcfunctionthistra...
...ssing exception missing description definedomquickstubs() define quick stubs on the given object, @a proto. [noscript,notxpcom] prbool definedomquickstubs( in jscontextptr cx, in jsobjectptr proto, in pruint32 flags, in pruint32 interfacecount, [array, size_is(interfacecount)] in nsiidptr interfacearray ); parameters cx a context. requires request. proto the (newly created) prototype object for a dom class. the js half of an xpcwrappednativeproto. flags property flags for the quick stub properties--should be either jsprop_enumerate or 0. interfacecount the number of interfaces the class implements. interfacearray the interfaces the class implements; interfacearray and interfacecount are like what nsiclassinfo.getinterfaces returns. return value missing description e...
...And 3 more matches

WebIDL bindings
ng a typeerror, you should use errorresult::throwtypeerror() instead of calling throw(). custom extended attributes our webidl parser and code generator recognize several extended attributes that are not present in the webidl spec. [alias=propname] this extended attribute can be specified on a method and indicates that another property with the specified name will also appear on the interface prototype object and will have the same function object value as the property for the method. for example: interface myinterface { [alias=performsomething] void dosomething(); }; myinterface.prototype.performsomething will have the same function object value as myinterface.prototype.dosomething. multiple [alias] extended attribute can be used on the one method. [alias] cannot be used on a static meth...
... cannot be used on a static method, nor on methods on a global interface (such as window). aside from regular property names, the name of an alias can be symbol.iterator. this is specified by writing [alias="@@iterator"]. [bindingalias=propname] this extended attribute can be specified on an attribute and indicates that another property with the specified name will also appear on the interface prototype object and will call the same underlying c++ implementation for the getter and setter. this is more efficient than using the same binaryname for both attributes, because it shares the binding glue code between them. the properties still have separate getter/setter functions in javascript, so from the point of view of web consumers it's as if you actually had two separate attribute declarations on...
...inaryname for both attributes, because it shares the binding glue code between them. the properties still have separate getter/setter functions in javascript, so from the point of view of web consumers it's as if you actually had two separate attribute declarations on your interface. for example: interface myinterface { [bindingalias=otherattr] readonly attribute boolean attr; }; myinterface.prototype.otherattr and myinterface.prototype.attr will both exist, have separate getter/setter functions, but call the same binding glue code and implementation function on the objects implementing myinterface. multiple [bindingalias] extended attributes can be used on a single attribute. [chromeonly] this extended attribute can be specified on any method, attribute, or constant on an interface or on a...
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Debugger.Frame - Firefox Developer Tools
ethods it triggers. even though the debuggee and debugger share the same javascript stack, frames pushed for spidermonkey’s calls to handler methods to report events in the debuggee are never considered visible frames.) invocation functions and “debugger” frames aninvocation function is any function in this interface that allows the debugger to invoke code in the debuggee: debugger.object.prototype.call, debugger.frame.prototype.eval, and so on. while invocation functions differ in the code to be run and how to pass values to it, they all follow this general procedure: letolder be the youngest visible frame on the stack, or null if there is no such frame. (this is never one of the the debugger’s own frames; those never appear as debugger.frame instances.) push a "debugger" fram...
...t visible frame on the stack, or null if there is no such frame. (this is never one of the the debugger’s own frames; those never appear as debugger.frame instances.) push a "debugger" frame on the stack, witholder as its older property. invoke the debuggee code as appropriate for the given invocation function, with the "debugger" frame as its continuation. for example, debugger.frame.prototype.eval pushes an "eval" frame for code it runs, whereas debugger.object.prototype.call pushes a "call" frame. when the debuggee code completes, whether by returning, throwing an exception or being terminated, pop the "debugger" frame, and return an appropriate completion value from the invocation function to the debugger. when a debugger calls an invocation function to run debuggee code, t...
...ate completion value from the invocation function to the debugger. when a debugger calls an invocation function to run debuggee code, that code’s continuation is the debugger, not the next debuggee code frame. pushing a "debugger" frame makes this continuation explicit, and makes it easier to find the extent of the stack created for the invocation. accessor properties of the debugger.frame prototype object a debugger.frame instance inherits the following accessor properties from its prototype: type a string describing what sort of frame this is: "call": a frame running a function call. (we may not be able to obtain frames for calls to host functions.) "eval": a frame running code passed to eval. "global": a frame running global code (javascript that is neither ...
...And 3 more matches

ChildNode.after() - Web APIs
r with the following code: // from: https://github.com/jserz/js_piece/blob/master/dom/childnode/after()/after().md (function (arr) { arr.foreach(function (item) { if (item.hasownproperty('after')) { return; } object.defineproperty(item, 'after', { configurable: true, enumerable: true, writable: true, value: function after() { var argarr = array.prototype.slice.call(arguments), docfrag = document.createdocumentfragment(); argarr.foreach(function (argitem) { var isnode = argitem instanceof node; docfrag.appendchild(isnode ? argitem : document.createtextnode(string(argitem))); }); this.parentnode.insertbefore(docfrag, this.nextsibling); } }); }); })([element.prototype, characterdata...
...slice.call(arguments), docfrag = document.createdocumentfragment(); argarr.foreach(function (argitem) { var isnode = argitem instanceof node; docfrag.appendchild(isnode ? ...
... docfrag = document.createdocumentfragment(); argarr.foreach(function (argitem) { var isnode = argitem instanceof node; docfrag.appendchild(isnode ? ...
...And 3 more matches

TextEncoder - Web APIs
mentation to support non-utf-8 text encodings on github. example const encoder = new textencoder() const view = encoder.encode('€') console.log(view); // uint8array(3) [226, 130, 172] constructor textencoder() returns a newly constructed textencoder that will generate a byte stream with utf-8 encoding. properties the textencoder interface doesn't inherit any property. ...
...') console.log(view); // uint8array(3) [226, 130, 172] constructor textencoder() returns a newly constructed textencoder that will generate a byte stream with utf-8 encoding. properties the textencoder interface doesn't inherit any property. textencoder.prototype.encodingread only always returns "utf-8". methods the textencoder interface doesn't inherit any method. textencoder.prototype.encode() takes a usvstring as input, and returns a uint8array containing utf-8 encoded text. textencoder.prototype.encodeinto() takes a usvstring to encode and a destination uint8array to put resulting utf-8 encoded text into, and returns a dictionary object indicating the progress of the encoding. this is potentially more performant than the older encode() method. polyfill the below polyfi...
...l might be impractical for large strings. finally, note that you should run the below code through a minifier (especially closure compiler) to turn sequences like 0x1e << 3 into 0xf0. these sequences are not already precomputed because they serve to aesthetically illustrate how the polyfill works. if (typeof textencoder === "undefined") { textencoder=function textencoder(){}; textencoder.prototype.encode = function encode(str) { "use strict"; var len = str.length, respos = -1; // the uint8array's length must be at least 3x the length of the string because an invalid utf-16 // takes up the equivelent space of 3 utf-8 characters to encode it properly. however, array's // have an auto expanding length and 1.5x should be just the right balance for most...
...And 3 more matches

WebGL model view projection - Web APIs
and uniform locations this.positionlocation = gl.getattriblocation(this.webglprogram, 'position'); this.colorlocation = gl.getuniformlocation(this.webglprogram, 'color'); // tell webgl to test the depth when drawing, so if a square is behind // another square it won't be drawn gl.enable(gl.depth_test); } webglbox draw now we'll create a method to draw a box on the screen. webglbox.prototype.draw = function(settings) { // create some attribute data; these are the triangles that will end being // drawn to the screen. there are two that form a square. var data = new float32array([ //triangle 1 settings.left, settings.bottom, settings.depth, settings.right, settings.bottom, settings.depth, settings.left, settings.top, settings.depth, //triangle 2 se...
...e shrunk down in order to not fill the entirety of clip space. this matrix is sent directly to the shader, having been multiplied in javascript beforehand. the following code sample defines a method on the cubedemo object that will create the model matrix. it uses custom functions to create and multiply matrices as defined in the mdn webgl shared code. ...
...efactor) then factoring out the scalefactor, we get this: w = (4 + 1) * scalefactor which is exactly the same as the (z + 1) * scalefactor that we used in the previous example. in the box demo, an additional computesimpleprojectionmatrix() method is added. this is called in the draw() method and has the scale factor passed to it. the result should be identical to the last example: cubedemo.prototype.computesimpleprojectionmatrix = function(scalefactor) { this.transforms.projection = [ 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1, scalefactor, 0, 0, 0, scalefactor ]; }; although the result is identical, the important step here is in the vertex shader. rather than modifying the vertex directly, it gets multiplied by an additional projection matrix, which (as the name suggests) projects 3d point...
...And 3 more matches

Using Web Workers - Web APIs
nctions takes at least one argument, the method name we want to query. then we can pass in the arguments that the method needs. */ this.sendquery = function() { if (arguments.length < 1) { throw new typeerror('queryableworker.sendquery takes at least one argument'); return; } worker.postmessage({ 'querymethod': arguments[0], 'queryarguments': array.prototype.slice.call(arguments, 1) }); } we finish queryableworker with the onmessage method. if the worker has the corresponding methods we queried, it should return the name of the corresponding listener and the arguments it needs, we just need to find it in listeners.: worker.onmessage = function(event) { if (event.data instanceof object && event.data.hasownproperty('querymethodlistene...
...printstuff', a - b); }, waitsometime: function() { settimeout(function() { reply('doalert', 3, 'seconds'); }, 3000); } } function reply() { if (arguments.length < 1) { throw new typeerror('reply - takes at least one argument'); return; } postmessage({ querymethodlistener: arguments[0], querymethodarguments: array.prototype.slice.call(arguments, 1) }); } /* this method is called when main page calls queryworker's postmessage method directly*/ function defaultreply(message) { // do something } and the onmessage method is now trivial: onmessage = function(event) { if (event.data instanceof object && event.data.hasownproperty('querymethod') && event.data.hasownproperty('querymethodargume...
... page): <!doctype html> <html> <head> <meta charset="utf-8" /> <title>mdn example - queryable worker</title> <script type="text/javascript"> /* queryableworker instances methods: * sendquery(queryable function name, argument to pass 1, argument to pass 2, etc. ...
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WindowOrWorkerGlobalScope.setTimeout() - Web APIs
ay[, arg1, arg2, ...]); |*| var intervalid = window.setinterval(code, delay); |*| \*/ (function() { settimeout(function(arg1) { if (arg1 === 'test') { // feature test is passed, no need for polyfill return; } var __nativest__ = window.settimeout; window.settimeout = function(vcallback, ndelay /*, argumenttopass1, argumenttopass2, etc. ...
... } : vcallback, ndelay); }; }, 0, 'test'); var interval = setinterval(function(arg1) { clearinterval(interval); if (arg1 === 'test') { // feature test is passed, no need for polyfill return; } var __nativesi__ = window.setinterval; window.setinterval = function(vcallback, ndelay /*, argumenttopass1, argumenttopass2, etc. ...
...ettimeout, then when it's called, its this is not set so it defaults to the window object. there's also no option to pass a thisarg to settimeout as there is in array methods like foreach, reduce, etc. and as shown below, using call to set this doesn't work either. ...
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RangeError: precision is out of range - JavaScript
f range (edge) rangeerror: precision {0} out of range (firefox) rangeerror: toexponential() argument must be between 0 and 20 (chrome) rangeerror: tofixed() digits argument must be between 0 and 20 (chrome) rangeerror: toprecision() argument must be between 1 and 21 (chrome) error type rangeerror what went wrong? ...
...on {0} out of range (firefox) rangeerror: toexponential() argument must be between 0 and 20 (chrome) rangeerror: tofixed() digits argument must be between 0 and 20 (chrome) rangeerror: toprecision() argument must be between 1 and 21 (chrome) error type rangeerror what went wrong? ...
...) rangeerror: toexponential() argument must be between 0 and 20 (chrome) rangeerror: tofixed() digits argument must be between 0 and 20 (chrome) rangeerror: toprecision() argument must be between 1 and 21 (chrome) error type rangeerror what went wrong? ...
...And 3 more matches

Intl.Locale - JavaScript
and numbering system type. traditionally, the intl api used strings to represent locales, just as unicode does. this is a simple and lightweight solution that works well. adding a locale class, however, adds ease of parsing and manipulating the language, script, and region, as well as extension tags. constructor intl.locale() creates a new locale object. ...
...tweight solution that works well. adding a locale class, however, adds ease of parsing and manipulating the language, script, and region, as well as extension tags. constructor intl.locale() creates a new locale object. instance properties intl.locale.prototype.basename returns basic, core information about the locale in the form of a substring of the complete data string. intl.locale.prototype.calendar returns the part of the locale that indicates the locale's calendar era. ...
...e language, script, and region, as well as extension tags. constructor intl.locale() creates a new locale object. instance properties intl.locale.prototype.basename returns basic, core information about the locale in the form of a substring of the complete data string. intl.locale.prototype.calendar returns the part of the locale that indicates the locale's calendar era. intl.locale.prototype.casefirst returns whether case is taken into account for the locale's collation rules. intl.locale.prototype.collation returns the collation type for the locale, which is used to order strings according to the locale's rules. ...
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Object.defineProperty() - JavaScript
descriptor has neither of value, writable, get and set keys, it is treated as a data descriptor. if a descriptor has both value or writable and get or set keys, an exception is thrown. bear in mind that these attributes are not necessarily the descriptor's own properties. inherited properties will be considered as well. in order to ensure these defaults are preserved, you might freeze the object.prototype upfront, specify all options explicitly, or point to null with object.create(null). // using __proto__ var obj = {}; var descriptor = object.create(null); // no inherited properties descriptor.value = 'static'; // not enumerable, not configurable, not writable as defaults object.defineproperty(obj, 'key', descriptor); // being explicit object.defineproperty(obj, 'key', { enumerable: false, ...
... d = withvalue.d || ( withvalue.d = { enumerable: false, writable: false, configurable: false, value: value } ); // avoiding duplicate operation for assigning value if (d.value !== value) d.value = value; return d; } // ... and ... object.defineproperty(obj, 'key', withvalue('static')); // if freeze is available, prevents adding or // removing the object prototype properties // (value, get, set, enumerable, writable, configurable) (object.freeze || object)(object.prototype); examples if you want to see how to use the object.defineproperty method with a binary-flags-like syntax, see additional examples. creating a property when the property specified doesn't exist in the object, object.defineproperty() creates a new property as described. fields may be...
...e assigned console.log(instance.myname); // this is my name string inheritance of properties if an accessor property is inherited, its get and set methods will be called when the property is accessed and modified on descendant objects. if these methods use a variable to store the value, this value will be shared by all objects. ...
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Comparing Reflect and Object methods - JavaScript
bject. returns undefined if it does not exist, and a typeerror if anything other than an object (a primitive) is passed in as the first argument. getownpropertydescriptors() object.getownpropertydescriptors() returns an object containing a property descriptor of each passed-in object. returns an empty object if the passed-in object has no owned property descriptors. ...
... it does not exist, and a typeerror if anything other than an object (a primitive) is passed in as the first argument. getownpropertydescriptors() object.getownpropertydescriptors() returns an object containing a property descriptor of each passed-in object. returns an empty object if the passed-in object has no owned property descriptors. ...
...typeerror if anything other than an object (a primitive) is passed in as the first argument. getownpropertydescriptors() object.getownpropertydescriptors() returns an object containing a property descriptor of each passed-in object. returns an empty object if the passed-in object has no owned property descriptors. n/a getprototypeof() object.getprototypeof() returns the prototype of the given object. ...
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Set - JavaScript
equality for -0 and 0" in the browser compatibility table for details. nan and undefined can also be stored in a set. all nan values are equated (i.e. nan is considered the same as nan, even though nan !== nan). constructor set() creates a new set object. static properties get set[@@species] the constructor function that is used to create derived objects. ...
... can also be stored in a set. all nan values are equated (i.e. nan is considered the same as nan, even though nan !== nan). constructor set() creates a new set object. static properties get set[@@species] the constructor function that is used to create derived objects. instance properties set.prototype.size returns the number of values in the set object. instance methods set.prototype.add(value) appends value to the set object. returns the set object. ...
... same as nan, even though nan !== nan). constructor set() creates a new set object. static properties get set[@@species] the constructor function that is used to create derived objects. instance properties set.prototype.size returns the number of values in the set object. instance methods set.prototype.add(value) appends value to the set object. returns the set object. set.prototype.clear() removes all elements from the set object. set.prototype.delete(value) removes the element associated to the value and returns the value that set.prototype.has(value) would have previously returned. set.prototype.has(value) will return false afterwards. set.prototype.has(value) returns a boolean asserting whether an element is present with the given value in the set object or not. i...
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Symbol - JavaScript
ax "new symbol()". static properties symbol.asynciterator a method that returns the default asynciterator for an object. used by for await...of. symbol.hasinstance a method determining if a constructor object recognizes an object as its instance. used by instanceof. symbol.isconcatspreadable a boolean value indicating if an object should be flattened to its array elements. used by array.prototype.concat(). symbol.iterator a method returning the default iterator for an object. used by for...of. symbol.match a method that matches against a string, also used to determine if an object may be used as a regular expression. used by string.prototype.match(). symbol.matchall a method that returns an iterator, that yields matches of the regular expression against a string. used by string.prot...
...mbol.match a method that matches against a string, also used to determine if an object may be used as a regular expression. used by string.prototype.match(). symbol.matchall a method that returns an iterator, that yields matches of the regular expression against a string. used by string.prototype.matchall(). symbol.replace a method that replaces matched substrings of a string. used by string.prototype.replace(). symbol.search a method that returns the index within a string that matches the regular expression. used by string.prototype.search(). symbol.split a method that splits a string at the indices that match a regular expression. used by string.prototype.split(). symbol.species a constructor function that is used to create derived objects. symbol.toprimitive a method converting an o...
... symbol.unscopables an object value of whose own and inherited property names are excluded from the with environment bindings of the associated object. static methods symbol.for(key) searches for existing symbols with the given key and returns it if found. otherwise a new symbol gets created in the global symbol registry with key. ...
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Spread syntax (...) - JavaScript
et objclone = { ...obj }; rest syntax (parameters) rest syntax looks exactly like spread syntax. in a way, rest syntax is the opposite of spread syntax. spread syntax "expands" an array into its elements, while rest syntax collects multiple elements and "condenses" them into a single element. see rest parameters. examples spread in function calls replace apply() it is common to use function.prototype.apply() in cases where you want to use the elements of an array as arguments to a function. function myfunction(x, y, z) { } const args = [0, 1, 2]; myfunction.apply(null, args); with spread syntax the above can be written as: function myfunction(x, y, z) { } const args = [0, 1, 2]; myfunction(...args); any argument in the argument list can use spread syntax, and the spread syntax can be used...
...sily used with new thanks to spread syntax: const datefields = [1970, 0, 1]; // 1 jan 1970 const d = new date(...datefields); to use new with an array of parameters without spread syntax, you would have to do it indirectly through partial application: function applyandnew(constructor, args) { function partial () { return constructor.apply(this, args); }; if (typeof constructor.prototype === "object") { partial.prototype = object.create(constructor.prototype); } return partial; } function myconstructor () { console.log("arguments.length: " + arguments.length); console.log(arguments); this.prop1="val1"; this.prop2="val2"; }; const myarguments = ["hi", "how", "are", "you", "mr", null]; const myconstructorwitharguments = applyandnew(myconstructor, myargume...
...fectively goes one level deep while copying an array. therefore, it may be unsuitable for copying multidimensional arrays, as the following example shows. (the same is true with object.assign() and spread syntax.) const a = [[1], [2], [3]]; const b = [...a]; b.shift().shift(); // 1 // oh no! now array 'a' is affected as well: a // [[], [2], [3]] a better way to concatenate arrays array.prototype.concat() is often used to concatenate an array to the end of an existing array. without spread syntax, this is done as: const arr1 = [0, 1, 2]; const arr2 = [3, 4, 5]; // append all items from arr2 onto arr1 arr1 = arr1.concat(arr2); with spread syntax this becomes: let arr1 = [0, 1, 2]; let arr2 = [3, 4, 5]; arr1 = [...arr1, ...arr2]; // arr1 is now [0, 1, 2, 3, 4, 5] // note: not to use ...
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Using the WebAssembly JavaScript API - WebAssembly
irst word of linear memory, you can do this: new uint32array(memory.buffer)[0] = 42; you can then return the same value using: new uint32array(memory.buffer)[0] try this now in your demo — save what you’ve added so far, load it in your browser, then try entering the above two lines in your javascript console. growing memory a memory instance can be grown by calls to memory.prototype.grow(), where again the argument is specified in units of webassembly pages: memory.grow(1); if a maximum value was supplied upon creation of the memory instance, attempts to grow past this maximum will throw a webassembly.rangeerror exception. the engine takes advantage of this supplied upper-bounds to reserve memory ahead of time, which can make resizing more efficient. note: since an arrayb...
...bassembly pages: memory.grow(1); if a maximum value was supplied upon creation of the memory instance, attempts to grow past this maximum will throw a webassembly.rangeerror exception. the engine takes advantage of this supplied upper-bounds to reserve memory ahead of time, which can make resizing more efficient. note: since an arraybuffer’s bytelength is immutable, after a successful memory.prototype.grow() operation the buffer getter will return a new arraybuffer object (with the new bytelength) and any previous arraybuffer objects become “detached”, or disconnected from the underlying memory they previously pointed to. just like functions, linear memories can be defined inside a module or imported. similarly, a module may also optionally export its memory. this means that javascript ca...
... from the underlying memory they previously pointed to. just like functions, linear memories can be defined inside a module or imported. similarly, a module may also optionally export its memory. this means that javascript can get access to the memory of a webassembly instance either by creating a new webassembly.memory and passing it in as an import or by receiving a memory export (via instance.prototype.exports). more involved memory example let’s make the above assertions clearer by looking at a more involved memory example — a webassembly module that imports the memory instance we defined earlier, populates it with an array of integers, then sums them. you can find this at memory.wasm. make a local copy of memory.wasm in the same directory as before. note: you can see the mod...
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Private Properties - Archive of obsolete content
prefix each private property name with an underscore. consider the following example: function point(x, y) { this._x = x; this._y = y; } the properties _x and _y are intended to be private, and should only be accessed by member functions. to make a private property readable/writable from any function, it's common to define getter/setter functions for the property, respectively: point.prototype.getx = function () { return this._x; }; point.prototype.setx = function (x) { this._x = x; }; point.prototype.gety = function () { return this._y; }; point.prototype.sety = function (y) { this._y = y; }; the above technique is simple and clearly expresses intent. however, the use of an underscore prefix is just a coding convention and is not enforced by the language: there is...
...bles: function point(_x, _y) { this.getx = function () { return _x; }; this.setx = function (x) { _x = x; }; this.gety = function () { return _y; }; this.sety = function (y) { _y = y; }; } note that this technique requires member functions that need access to private properties to be defined on the object itself, instead of its prototype. this is slightly less efficient than using the underscore convention, but not significantly for most applications. the advantage of this technique is that it offers more protection: there is no way for the user to access a private property, except by using its getter or setter function. however, the use of closures makes private properties too restrictive: since there is no way to access variab...
...ingle object, called a namespace, and then store the namespace as a private property on the original object. ...
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test/assert - Archive of obsolete content
t, as determined by ===. if the expected value is a date object, the actual value is equivalent if it is also a date object that refers to the same time. other pairs that do not both pass typeof value == "object", equivalence is determined by ==. for all other object pairs, including array objects, equivalence is determined by having the same number of owned properties (as verified with object.prototype.hasownproperty.call), the same set of keys (although not necessarily the same order), equivalent values for every corresponding key, and an identical "prototype" property. note: this accounts for both named and indexed properties on arrays. assert.deepequal({ a: "foo" }, { a: "foo" }, "equivalent objects"); parameters actual : object the actual result. expected : object the expected resul...
... expected : object the expected result. message : string optional message to log, providing extra information about the test. notdeepequal(actual, expected, message) tests that two objects do not have a deep equality relation, using the negation of the test for deep equality: assert.notdeepequal({ a: "foo" }, object.create({ a: "foo" }), "object's inherit from different prototypes"); parameters actual : object the actual result. expected : object the expected result. message : string optional message to log, providing extra information about the test. strictequal(actual, expected, message) tests that two objects are equal, using the strict equality operator ===: // this test will pass, because "==" will perform type conversion exports["test coercive equality"] =...
... the object returned by that function. ...
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QuerySelector - Archive of obsolete content
along the lines of other frameworks such as jquery or prototype, shortening the "queryselector" name can be convenient: function $ (selector, el) { if (!el) {el = document;} return el.queryselector(selector); } function $$ (selector, el) { if (!el) {el = document;} return el.queryselectorall(selector); // note: the returned object is a nodelist. ...
...the "queryselector" name can be convenient: function $ (selector, el) { if (!el) {el = document;} return el.queryselector(selector); } function $$ (selector, el) { if (!el) {el = document;} return el.queryselectorall(selector); // note: the returned object is a nodelist. ...
... // if you'd like to convert it to a array for convenience, use this instead: // return array.prototype.slice.call(el.queryselectorall(selector)); } alert($('#myid').id); (note that while using the firefox web console, the above functions are available automatically.) both xul and even xml can be easily made supportable (an alternative approach to the following would be to add chromewindow.prototype or window.prototype, accessing this.document.queryselector, or following the jquery style of chaining by returning 'this' within each prototype method of $()): htmldocument.prototype.$ = function (selector) { // only for html return this.queryselector(selector); }; example: <h1>test!</h1> <script> htmldocument.prototype.$ = function (selector) { return this.queryselector(selector); }; a...
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2D maze game with device orientation - Game development
eloader will load all of the assets like graphics and audio, mainmenu is the menu with the start button, howto shows the "how to play" instructions and the game state lets you actually play the game. let's quickly go though the content of those states. boot.js the boot state is the first one in the game. ...
...first that will be used later in the preload state to show the progress of loading all the other assets. the create function holds some basic configuration: we're setting up the scaling and alignment of the canvas, and moving on to the preload state when everything's ready. preloader.js the preloader state takes care of loading all the assets: ball.preloader = function(game) {}; ball.preloader.prototype = { preload: function() { this.preloadbg = this.add.sprite((ball._width-297)*0.5, (ball._height-145)*0.5, 'preloaderbg'); this.preloadbar = this.add.sprite((ball._width-158)*0.5, (ball._height-50)*0.5, 'preloaderbar'); this.load.setpreloadsprite(this.preloadbar); this.load.image('ball', 'img/ball.png'); // ... this.load.spritesheet('button-star...
...s is visualized by the framework with the use of one image. with every asset loaded you can see more of the preloadbar image: from 0% to 100%, updated on every frame. after all the assets are loaded, the mainmenu state is launched. mainmenu.js the mainmenu state shows the main menu of the game, where you can start playing by clicking the button. ...
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Object building practice - Learn web development
ed to the x/y coordinate values when we animate the balls, to move them by this much on each frame. color — each ball gets a color. size — each ball gets a size — this is its radius, in pixels. this handles the properties, but what about the methods? we want to get our balls to actually do something in our program. drawing the ball first add the following draw() method to the ball()'s prototype: ball.prototype.draw = function() { ctx.beginpath(); ctx.fillstyle = this.color; ctx.arc(this.x, this.y, this.size, 0, 2 * math.pi); ctx.fill(); } using this function, we can tell the ball to draw itself onto the screen, by calling a series of members of the 2d canvas context we defined earlier (ctx). the context is like the paper, and now we want to command our pen to draw something on...
... members: testball.x testball.size testball.color testball.draw() when you enter the last line, you should see the ball draw itself somewhere on the canvas. updating the ball's data we can draw the ball in position, but to actually move the ball, we need an update function of some kind. ...
...all.x testball.size testball.color testball.draw() when you enter the last line, you should see the ball draw itself somewhere on the canvas. updating the ball's data we can draw the ball in position, but to actually move the ball, we need an update function of some kind. ...
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JSAPI User Guide
_*stub function pointers. */ my_addproperty, my_delproperty, my_getproperty, my_setproperty, my_enumerate, my_resolve, my_convert, my_finalize }; jsobject *obj; /* * define an object named in the global scope that can be enumerated by * for/in loops. the parent object is passed as the second argument, as * with all other api calls that take an object/name pair. the prototype * passed in is null, so the default object prototype will be used. */ obj = js_defineobject(cx, globalobj, "myobject", &my_class, nullptr, jsprop_enumerate); /* * define a bunch of properties with a jspropertyspec array statically * initialized and terminated with a null-name entry. besides its name, * each property has a "tiny" identifier (my_color, e.g.) that can be...
...se my_color: *vp = . . .; break; case my_height: *vp = . . .; break; case my_width: *vp = . . .; break; case my_funny: *vp = . . .; break; case my_array: *vp = . . .; break; case my_rdonly: *vp = . . .; break; } } return true; } defining classes this pulls together the above api elements by defining a constructor function, a prototype object, and properties of the prototype and of the constructor, all with one api call. initialize a class by defining its constructor function, prototype, and per-instance and per-class properties. the latter are called "static" below by analogy to java. they are defined in the constructor object's scope, so that myclass.mystaticprop works along with new myclass(). js_initclass takes a lot of a...
... lot of arguments, but you can pass nullptr for any of the last four if there are no such properties or methods. ...
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JS_ConstructObject
moved from the jsapi. the preferred alternative is to save a copy of the constructor function for the class, then to call it using js_new. a less-preferred short-term solution might be to use this reimplementation of the method, but note that this reimplementation is not guaranteed to continue working across spidermonkey releases. create a new object of the specified class, with the specified prototype and parent, then invokes a constructor function to initialize the new object. syntax jsobject * js_constructobject(jscontext *cx, jsclass *clasp, jsobject *proto, jsobject *parent); jsobject * js_constructobjectwitharguments(jscontext *cx, jsclass *clasp, jsobject *proto, jsobject *parent, unsigned int argc, jsval *argv); name type description cx jscontext ...
...pe description cx jscontext * the context in which to create the new object. requires request. in a js_threadsafe build, the caller must be in a request on this jscontext. clasp jsclass * pointer to the class to use for the new object. if this is null, an ordinary javascript object is created. proto jsobject * the object to serve as the new object's prototype, or null. parent jsobject * the object to serve as the new object's parent, or null. argc unsigned int (only in js_constructobjectwitharguments) the number of arguments to pass to the constructor. argv jsval * (only in js_constructobjectwitharguments) the array of arguments to pass to the constructor. this may be null if argc is zero. otherwise, the fi...
...l * (only in js_constructobjectwitharguments) the array of arguments to pass to the constructor. this may be null if argc is zero. otherwise, the first argc elements of this array must be populated with valid jsval values. the caller does not need to ensure that the array elements are rooted. description js_constructobject creates a new object of the specified class, with the specified prototype and parent, then invokes a constructor function to initialize the new object. cx is a pointer to a context associated with the runtime in which to create the new object. clasp is a pointer to the class of object to create. proto and parent may specify objects to be used as the new object's prototype and parent. if either is null, the engine tries to find reasonable defaults. js_constructobjectwi...
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JSAPI reference
e added in spidermonkey 17 js_reporterror js_reportwarning js_reporterrornumber js_reporterrornumberuc js_reporterrorflagsandnumber js_reporterrorflagsandnumberuc js_reporterrornumberucarray added in spidermonkey 24 js_reportoutofmemory js_reportallocationoverflow added in spidermonkey 1.8 js_geterrorreporter js_seterrorreporterobsolete since jsapi 52 js_errorfromexception js_geterrorprototype jsreport_is_exception jsreport_is_strict jsreport_is_warning jsreport_is_strict_mode_error the following functions allow c/c++ functions to throw and catch javascript exceptions: js::createerror added in spidermonkey 38 js_isexceptionpending js_getpendingexception js_setpendingexception js_clearpendingexception js_throwstopiteration added in spidermonkey 1.8 js_isstopiteration adde...
...ject js_newobject js_newplainobject added in spidermonkey 38 js_newobjectforconstructor added in spidermonkey 1.8.5 js_newglobalobject added in spidermonkey 1.8 js_newobjectwithgivenproto js_new added in spidermonkey 1.8 js_isglobalobject added in jsapi 24 js_constructobject obsolete since jsapi 16 js_constructobjectwitharguments obsolete since jsapi 16 js_getclass js_getobjectprototype added in jsapi 17 js_getfunctionprototype added in spidermonkey 17 js_getarrayprototype added in spidermonkey 24 js_getconstructor js_getglobalforobject js_getinstanceprivate js_getprototype js_setprototype js_getprivate js_setprivate js_freezeobject added in spidermonkey 1.8.5 js_deepfreezeobject added in spidermonkey 1.8.5 js_isextensible added in spidermonkey 1.8.5 js_preventexten...
...ermonkey 17 js::toprimitiveadded in spidermonkey 45 js::newfunctionfromspecadded in spidermonkey 45 js_defaultvalueobsolete since jsapi 44 js_get_class obsolete since jsapi 13 js_sealobject obsolete since javascript 1.8.5 js_getparent obsolete since jsapi 39 js_setparent obsolete since jsapi 39 standard objects enum jsprotokey added in spidermonkey 24 js_getclassobject js_getclassprototype js::protokeytoid added in spidermonkey 38 js_idtoprotokey added in spidermonkey 31 js::identifystandardinstance added in spidermonkey 31 js::identifystandardprototype added in spidermonkey 31 js::identifystandardinstanceorprototype added in spidermonkey 31 js::identifystandardconstructor added in spidermonkey 38 date js_newdateobject added in spidermonkey 1.8.5 js_newdateobjectmsec ad...
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Building an Account Manager Extension
ent the nsiaccountmanagerextension. we name the extension "devmo-account" and state that it is located in the chrome package "example@mozilla.org". furthermore we show the new panel only for imap accounts... components.utils.import("resource://gre/modules/xpcomutils.jsm"); //class constructor function devmoaccountmanagerextension() {}; // class definition devmoaccountmanagerextension.prototype = { name : "devmo-account", chromepackagename : "example@mozilla.org", showpanel: function(server) { //this panel is only shown for imap accounts... if (server.type == \"imap\") return true; return false; }, queryinterface: xpcomutils.generateqi([ components.interfaces.nsimsgaccountmanagerextension ]) } step 2: building a componen...
...nd register it in the component manager as account manager extension. therefore we add the following code to the previous. the javascript file has to be saved either in the extension's or thunderbird's component directory. // define the contract information needed for this component... // ... the unique component identifier (change it if you copied this example!)... ...
...file has to be saved either in the extension's or thunderbird's component directory. // define the contract information needed for this component... // ... the unique component identifier (change it if you copied this example!)... devmoaccountmanagerextension.prototype.classid = components.id("{659ce960-9dfb-11dd-ad8b-0800200c9a55}"); // ... the description and ... devmoaccountmanagerextension.prototype.classdescription = "devmo account manager extension"; // ... textual unique identifier or rendez-vous point in the category manager. ...
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File - Web APIs
height="50" fill="#f4f7f8" stroke="#d4dde4" stroke-width="2px" /><text x="153.5" y="30" font-size="12px" font-family="consolas,monaco,andale mono,monospace" fill="#4d4e53" text-anchor="middle" alignment-baseline="middle">file</text></a></svg></div> a:hover text { fill: #0095dd; pointer-events: all;} constructor file() returns a newly constructed file. ...
...ace" fill="#4d4e53" text-anchor="middle" alignment-baseline="middle">file</text></a></svg></div> a:hover text { fill: #0095dd; pointer-events: all;} constructor file() returns a newly constructed file. instance properties file.prototype.lastmodified read only returns the last modified time of the file, in millisecond since the unix epoch (january 1st, 1970 at midnight). file.prototype.lastmodifieddate read only returns the last modified date of the file referenced by the file object. ...
... #0095dd; pointer-events: all;} constructor file() returns a newly constructed file. instance properties file.prototype.lastmodified read only returns the last modified time of the file, in millisecond since the unix epoch (january 1st, 1970 at midnight). file.prototype.lastmodifieddate read only returns the last modified date of the file referenced by the file object. file.prototype.nameread only returns the name of the file referenced by the file object. file.prototype.webkitrelativepath read only returns the path the url of the file is relative to. ...
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Border-image generator - CSS: Cascading Style Sheets
lider_right.classname = 'ui-input-slider-right'; if (name) { var info = document.createelement('span'); info.classname = 'ui-input-slider-info'; info.textcontent = name; node.appendchild(info); } node.appendchild(slider_left); node.appendchild(input); node.appendchild(slider_right); this.input = input; sliders[topic] = this; setvalue(topic, value); }; inputslider.prototype.setinputvalue = function setinputvalue() { this.input.value = this.value.tofixed(this.precision) + this.unit; }; var setvalue = function setvalue(topic, value, send_notify) { var slider = sliders[topic]; if (slider === undefined) return; value = parsefloat(value.tofixed(slider.precision)); if (value > slider.max) value = slider.max; if (value < slider.min) value = slider.min; ...
...0 : 1; else this.state = 1 ^ this.state; if (active !== this) { if (active) active.toggle(false); active = this; } if (this.state === 0) this.dropmenu.setattribute('data-hidden', 'true'); else this.dropmenu.removeattribute('data-hidden'); }; var clickout = func...
...!== this) { if (active) active.toggle(false); active = this; } if (this.state === 0) this.dropmenu.setattribute('data-hidden', 'true'); else this.dropmenu.removeattribute('data-hidden'); }; var clickout = function clickout(e) { if (active.state === 0 || e.target === active.dropmenu || e.target === active.select) return; active.toggle(false); }; dropdown.prototype.updatevalue = function updatevalue(e) { if (date.now() - this.time < 500) return; if (e.target.classname !== "ui-dropdown-list") { this.setnodevalue(e.target); this.toggle(false); } this.time = date.now(); }; dropdown.prototype.setnodevalue = function setnodevalue(node) { this.value['name'] = node.textcontent; this.value['value'] = node.getattribute('data-value'); th...
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Regular expressions - JavaScript
a variable. advanced searching with flags regular expressions have six optional flags that allow for functionality like global and case insensitive searching. these flags can be used separately or together in any order, and are included as part of the regular expression. regular expression flags flag description corresponding property g global search. ...
...ave six optional flags that allow for functionality like global and case insensitive searching. these flags can be used separately or together in any order, and are included as part of the regular expression. regular expression flags flag description corresponding property g global search. regexp.prototype.global i case-insensitive search. regexp.prototype.ignorecase m multi-line search. ...
...and case insensitive searching. these flags can be used separately or together in any order, and are included as part of the regular expression. regular expression flags flag description corresponding property g global search. regexp.prototype.global i case-insensitive search. regexp.prototype.ignorecase m multi-line search. regexp.prototype.multiline s allows . to match newline characters. ...
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Public class fields - JavaScript
ations are an experimental feature (stage 3) proposed at tc39, the javascript standards committee. support in browsers is limited, but the feature can be used through a build step with systems like babel. see the compat information below. both static and instance public fields are writable, enumerable, and configurable properties. as such, unlike their private counterparts, they participate in prototype inheritance. syntax class classwithinstancefield { instancefield = 'instance field' } class classwithstaticfield { static staticfield = 'static field' } class classwithpublicinstancemethod { publicmethod() { return 'hello world' } } examples public static fields public static fields are useful when you want a field to exist only once per class, not on every class instance you ...
...ld.staticfield) // expected output: "static field"​ fields without initializers are initialized to undefined. class classwithstaticfield { static staticfield } console.assert(classwithstaticfield.hasownproperty('staticfield')) console.log(classwithstaticfield.staticfield) // expected output: "undefined" public static fields are not reinitialized on subclasses, but can be accessed via the prototype chain. class classwithstaticfield { static basestaticfield = 'base field' } class subclasswithstaticfield extends classwithstaticfield { static substaticfield = 'sub class field' } console.log(subclasswithstaticfield.substaticfield) // expected output: "sub class field" console.log(subclasswithstaticfield.basestaticfield) // expected output: "base field" when initializing fields, this re...
...d. const prefix = 'prefix' class classwithcomputedfieldname { [`${prefix}field`] = 'prefixed field' } const instance = new classwithcomputedfieldname() console.log(instance.prefixfield) // expected output: "prefixed field" when initializing fields this refers to the class instance under construction. just as in public instance methods, if you're in a subclass you can access the superclass prototype using super. class classwithinstancefield { baseinstancefield = 'base field' anotherbaseinstancefield = this.baseinstancefield baseinstancemethod() { return 'base method output' } } class subclasswithinstancefield extends classwithinstancefield { subinstancefield = super.baseinstancemethod() } const base = new classwithinstancefield() const sub = new subclasswithinstancefield() consol...
...And 2 more matches

Deprecated and obsolete features - JavaScript
irefox 33) escape sequences octal escape sequences (\ followed by one, two, or three octal digits) are deprecated in string and regular expression literals. the escape and unescape functions are deprecated. use encodeuri, encodeuricomponent, decodeuri or decodeuricomponent to encode and decode escape sequences for special characters. ...
...nces octal escape sequences (\ followed by one, two, or three octal digits) are deprecated in string and regular expression literals. the escape and unescape functions are deprecated. use encodeuri, encodeuricomponent, decodeuri or decodeuricomponent to encode and decode escape sequences for special characters. string methods html wrapper methods like string.prototype.fontsize and string.prototype.big. ...
...quences (\ followed by one, two, or three octal digits) are deprecated in string and regular expression literals. the escape and unescape functions are deprecated. use encodeuri, encodeuricomponent, decodeuri or decodeuricomponent to encode and decode escape sequences for special characters. string methods html wrapper methods like string.prototype.fontsize and string.prototype.big. string.prototype.quote is removed from firefox 37. ...
...And 2 more matches

TypeError: More arguments needed - JavaScript
the javascript exception "more arguments needed" occurs when there is an error with how a function is called. more arguments need to be provided. message typeerror: argument is not an object and is not null (edge) typeerror: object.create requires at least 1 argument, but only 0 were passed typeerror: object.setprototypeof requires at least 2 arguments, but only 0 were passed typeerror: object.defineproperties requires at least 1 argument, but only 0 were passed error type typeerror. ...
...totypeof requires at least 2 arguments, but only 0 were passed typeerror: object.defineproperties requires at least 1 argument, but only 0 were passed error type typeerror. what went wrong? there is an error with how a function is called. more arguments need to be provided. ...
...nt wrong? there is an error with how a function is called. more arguments need to be provided. ...
...And 2 more matches

Proxy - JavaScript
lidator); person.age = 100; console.log(person.age); // 100 person.age = 'young'; // throws an exception person.age = 300; // throws an exception extending constructor a function proxy could easily extend a constructor with a new constructor. this example uses the construct and apply handlers. ...
...log(person.age); // 100 person.age = 'young'; // throws an exception person.age = 300; // throws an exception extending constructor a function proxy could easily extend a constructor with a new constructor. this example uses the construct and apply handlers. ...
....age = 'young'; // throws an exception person.age = 300; // throws an exception extending constructor a function proxy could easily extend a constructor with a new constructor. this example uses the construct and apply handlers. ...
...And 2 more matches

Reflect.construct() - JavaScript
the static reflect.construct() method acts like the new operator, but as a function. it is equivalent to calling new target(...args). it gives also the added option to specify a different prototype. the source for this interactive example is stored in a github repository. if you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request. syntax reflect.construct(target, argumentslist[, newtarget]) parameters target the target function to call. argumentslist an array-like object specifying the arguments with which target should be called. newtarget optional the constructor whose prototype should be used. see also the new.target operator. if newtarget is not present, its value defaults to target. retu...
....construct() allows you to invoke a constructor with a variable number of arguments. ...
... prior to the introduction of reflect, objects could be constructed using an arbitrary combination of constructor and prototype by using object.create(). ...
...And 2 more matches

Symbol.toStringTag - JavaScript
the symbol.tostringtag well-known symbol is a string valued property that is used in the creation of the default string description of an object. it is accessed internally by the object.prototype.tostring() method. the source for this interactive example is stored in a github repository. if you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request. ...
...le is stored in a github repository. if you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request. property attributes of symbol.tostringtag writable no enumerable no configurable no examples default tags object.prototype.tostring.call('foo'); // "[object string]" object.prototype.tostring.call([1, 2]); // "[object array]" object.prototype.tostring.call(3); // "[object number]" object.prototype.tostring.call(true); // "[object boolean]" object.prototype.tostring.call(undefined); // "[object undefined]" object.prototype.tostring.call(null); // "[object null]" // ... and more built-in tost...
... // "[object string]" object.prototype.tostring.call([1, 2]); // "[object array]" object.prototype.tostring.call(3); // "[object number]" object.prototype.tostring.call(true); // "[object boolean]" object.prototype.tostring.call(undefined); // "[object undefined]" object.prototype.tostring.call(null); // "[object null]" // ... and more built-in tostringtag symbols object.prototype.tostring.call(new map()); // "[object map]" object.prototype.tostring.call(function* () {}); // "[object generatorfunction]" object.prototype.tostring.call(promise.resolve()); // "[object promise]" // ... ...
...And 2 more matches

SyntaxError - JavaScript
the syntaxerror object represents an error when trying to interpret syntactically invalid code. it is thrown when the javascript engine encounters tokens or token order that does not conform to the syntax of the language when parsing code. constructor syntaxerror() creates a new syntaxerror object. instance properties syntaxerror.prototype.message error message. ...
...t is thrown when the javascript engine encounters tokens or token order that does not conform to the syntax of the language when parsing code. constructor syntaxerror() creates a new syntaxerror object. instance properties syntaxerror.prototype.message error message. although ecma-262 specifies that syntaxerror should provide its own message property, in spidermonkey, it inherits error.prototype.message. syntaxerror.prototype.name error name. inherited from error. syntaxerror.prototype.filename path to file that raised this error. ...
...inherited from error. ...
...And 2 more matches

for...in - JavaScript
for (variable in object) statement variable a different property name is assigned to variable on each iteration. object object whose non-symbol enumerable properties are iterated over. description a for...in loop only iterates over enumerable, non-symbol properties. objects created from built–in constructors like array and object have inherited non–enumerable properties from object.prototype and string.prototype, such as string's indexof() method or object's tostring() method. the loop will iterate over all enumerable properties of the object itself and those the object inherits from its prototype chain (properties of nearer prototypes take precedence over those of prototypes further away from the object in its prototype chain). deleted, added, or modified properties a for...in loo...
...for...in will return the indexes in any particular order. the for...in loop statement will return all enumerable properties, including those with non–integer names and those that are inherited. because the order of iteration is implementation-dependent, iterating over an array may not visit elements in a consistent order. therefore, it is better to use a for loop with a numeric index (or array.prototype.foreach() or the for...of loop) when iterating over arrays where the order of access is important. iterating over own properties only if you only want to consider properties attached to the object itself, and not its prototypes, use getownpropertynames() or perform a hasownproperty() check (propertyisenumerable() can also be used). alternatively, if you know there won't be any outside code inte...
...hen iterating over arrays where the order of access is important. iterating over own properties only if you only want to consider properties attached to the object itself, and not its prototypes, use getownpropertynames() or perform a hasownproperty() check (propertyisenumerable() can also be used). alternatively, if you know there won't be any outside code interference, you can extend built-in prototypes with a check method. ...
...And 2 more matches

for...of - JavaScript
in these cases, the iterator is closed. function* foo(){ yield 1; yield 2; yield 3; }; for (const o of foo()) { ...
...over something. the main difference between them is in what they iterate over. the for...in statement iterates over the enumerable properties of an object, in an arbitrary order. the for...of statement iterates over values that the iterable object defines to be iterated over. the following example shows the difference between a for...of loop and a for...in loop when used with an array. ...
... them is in what they iterate over. the for...in statement iterates over the enumerable properties of an object, in an arbitrary order. the for...of statement iterates over values that the iterable object defines to be iterated over. the following example shows the difference between a for...of loop and a for...in loop when used with an array. ...
...And 2 more matches

core/namespace - Archive of obsolete content
aces for objects, which effectively may be used for creating fields that are not part of objects public api. let { ns } = require('sdk/core/namespace'); let anamespace = ns(); anamespace(publicapi).secret = secret; one namespace may be used with multiple objects: let { ns } = require('sdk/core/namespace'); let dom = ns(); function view(element) { let view = object.create(view.prototype); dom(view).element = element; // .... } view.prototype.destroy = function destroy() { let { element } = dom(this); element.parentnode.removechild(element); // ... }; // ... exports.view = view; // ... also, multiple namespaces can be used with one object: // ./widget.js let { cu } = require('chrome'); let { ns } = require('sdk/core/namespace'); let { vi...
...tiple namespaces can be used with one object: // ./widget.js let { cu } = require('chrome'); let { ns } = require('sdk/core/namespace'); let { view } = require('./view'); // note this is completely independent from view's internal namespace object. ...
...ew } = require('./view'); // note this is completely independent from view's internal namespace object. let sandboxes = ns(); function widget(options) { let { element, contentscript } = options; let widget = object.create(widget.prototype); view.call(widget, options.element); sandboxes(widget).sandbox = cu.sandbox(element.ownerdocument.defaultview); // ... } widget.prototype = object.create(view.prototype); widget.prototype.postmessage = function postmessage(message) { let { sandbox } = sandboxes(this); sandbox.postmessage(json.stringify(json.parse(message))); ... }; widget.prototype.destroy = function destroy() { view.prototype.destroy.call(this); // ... delete sandboxes(this).sandbox; }; exports.widget = widget; in addition access...
...dbox.postmessage(json.stringify(json.parse(message))); ... }; widget.prototype.destroy = function destroy() { view.prototype.destroy.call(this); // ... delete sandboxes(this).sandbox; }; exports.widget = widget; in addition access to the namespace can be shared with other code by just handing them a namespace accessor function. ...

core/promise - Archive of obsolete content
async(url); timeout(tweets, 20).then(function(data) { ui.display(data); }, function() { alert('network is being too slow, try again later'); }); alternative promise apis there may be cases where you will want to provide more than just then method on your promises. in fact some other promise frameworks do that. such use cases are also supported. ...
... being too slow, try again later'); }); alternative promise apis there may be cases where you will want to provide more than just then method on your promises. in fact some other promise frameworks do that. such use cases are also supported. earlier described defer may be passed optional prototype argument, in order to make the returned promise and all the subsequent promises decendents of that prototype: let { promise, resolve } = defer({ get: function get(name) { return this.then(function(value) { return value[name]; }); } }); promise.get('foo').get('bar').then(console.log); resolve({ foo: { bar: 'taram !!' } }); // => 'taram !!' also promised function maybe be passed a second optional prototype argument to achieve the same effect. treat all values as promises module pro...
...r second = resolve(b).then(function(bvalue) { return !!bvalue }); return resolve(a).then(function(avalue) { return !!avalue || second; }, function() { return second; }) } note: we could not use promised function here, as they reject returned promise if any of the given arguments is rejected. if you need to customize your promises even further you may pass resolve a second optional prototype argument that will have same effect as with defer. treat errors as promises now that we can create all kinds of eventual values, it's useful to have a way to create eventual errors. module exports reject to do exactly that. it takes anything as an argument and returns a promise that is rejected with it. const { reject } = require('sdk/core/promise'); var boom = reject(error('boom!')); future...
... it's useful to have a way to create eventual errors. module exports reject to do exactly that. it takes anything as an argument and returns a promise that is rejected with it. const { reject } = require('sdk/core/promise'); var boom = reject(error('boom!')); future(function() { return math.random() < 0.5 ? boom : value }) as with the rest of the apis a reject may be given a second optional prototype argument to customize resulting promise to your needs. ...

Canvas code snippets - Archive of obsolete content
}; } chaining methods this class provides jquery-style chained access to 2d context methods and properties. ...
...rgradient', 'createradialgradient', 'getimagedata', 'putimagedata' ]; var props = ['canvas', 'fillstyle', 'font', 'globalalpha', 'globalcompositeoperation', 'linecap', 'linejoin', 'linewidth', 'miterlimit', 'shadowoffsetx', 'shadowoffsety', 'shadowblur', 'shadowcolor', 'strokestyle', 'textalign', 'textbaseline']; for (let m of methods) { let method = m; canvas2dcontext.prototype[method] = function() { this.ctx[method].apply(this.ctx, arguments); return this; }; } for (let m of gettermethods) { let method = m; canvas2dcontext.prototype[method] = function() { return this.ctx[method].apply(this.ctx, arguments); }; } for (let p of props) { let prop = p; canvas2dcontext.prototype[prop] = function(value) { if (value ===...
...rence to the iframe's window and draws this window to a canvas object. note that this only works if you are running the page from chrome. if you try running the code as a plain webpage, you will get a 'security error" code: "1000' error. remotecanvas = function() { this.url = 'http://developer.mozilla.org'; }; remotecanvas.canvas_width = 300; remotecanvas.canvas_height = 300; remotecanvas.prototype.load = function() { var windowwidth = window.innerwidth - 25; var iframe; iframe = document.createelement('iframe'); iframe.id = 'test-iframe'; iframe.height = '10px'; iframe.width = windowwidth + 'px'; iframe.style.visibility = 'hidden'; iframe.src = this.url; // here is where the magic happens... add a listener to the // frame's onload event iframe.ad...
... iframe.height = '10px'; iframe.width = windowwidth + 'px'; iframe.style.visibility = 'hidden'; iframe.src = this.url; // here is where the magic happens... ...

Appendix D: Loading Scripts - Archive of obsolete content
s, including the url, line number, and javascript version of the file from which the code being evaluated was extracted. this information is invaluable for debugging, and the flexibility with which it can be specified makes this method useful for extracting javascript from a number of file formats other than raw javascript scripts. additionally, as sandbox objects can be created with an arbitrary prototype object, the evaluated code can be given access to the global properties of any existing scope. security: sandbox objects are initialized with a security principal object, or otherwise a window or url from which to derive one. this means that evalinsandbox can be used to execute code with a specified privilege level rather than full chrome privileges. beyond this, the scope of the sandbox can be ...
... // use the current content window as the execution context. // to make properties defined by scripts executing on the page // available to your sandbox script, use content.wrappedjsobject // instead. let context = content; // create the sandbox let sandbox = components.utils.sandbox(context, { // make properties of the context object available via the // script's global scope sandboxprototype: context, // wrap objects retrieved from the sandbox in xpcnativewrappers. // this is the default action. wantxrays: true }); // the script that will be executed: let script = string(); // evaluate the script: components.utils.evalinsandbox(script, sandbox, // the javascript version "1.8", /...
...ut will still be wrapped in inter-compartment proxies. ...
...e current script and will have access to the same globals, but any new globals it creates will be accessible only to the script itself. objects passed out of the sandbox will not be wrapped in xpcnativewrappers but will still be wrapped in inter-compartment proxies. ...

ECMAScript 2016 to ES.Next support in Mozilla - Archive of obsolete content
, and es2018 have been released. this year, the es2019 specification will be released and es2020 is the current ecmascript draft specification. you can see the latest proposals on the tc39/ecma262 github repository. a channel for feedback on ecmascript standards is es-discuss. below is a list of features in es2016+ and what version of firefox they were implemented in. ...
...e es2019 specification will be released and es2020 is the current ecmascript draft specification. you can see the latest proposals on the tc39/ecma262 github repository. a channel for feedback on ecmascript standards is es-discuss. below is a list of features in es2016+ and what version of firefox they were implemented in. ...
...pository. a channel for feedback on ecmascript standards is es-discuss. below is a list of features in es2016+ and what version of firefox they were implemented in. ...
...cript standards is es-discuss. below is a list of features in es2016+ and what version of firefox they were implemented in. ...

Index - MDN Web Docs Glossary: Definitions of Web-related terms
codingscripting, glossary, javascript in javascript, a primitive (primitive value, primitive data type) is data that is not an object and has no methods. there are 6 primitive data types: string, number, bigint, boolean, undefined, and symbol. there also is null, which is seemingly primitive, but indeed is a special case for every object: and any structured type is derived from null by the prototype chain. 332 privileged glossary, security users are said to be privileged when they are granted additional rights to a system, or given ultimate access to content in a higher priority level when compared to normal users. 333 progressive enhancement accessibility, design, glossary progressive enhancement is a design philosophy that provides a baseline of es...
... attributes associated with a data structure. 339 protocol glossary, infrastructure, protocols a protocol is a system of rules that define how data is exchanged within or between computers. communications between devices require that the devices agree on the format of the data that is being exchanged. the set of rules that defines a format is called a protocol. ...
... 339 protocol glossary, infrastructure, protocols a protocol is a system of rules that define how data is exchanged within or between computers. communications between devices require that the devices agree on the format of the data that is being exchanged. the set of rules that defines a format is called a protocol. ...
... between computers. communications between devices require that the devices agree on the format of the data that is being exchanged. the set of rules that defines a format is called a protocol. 340 prototype apps, composing, glossary a prototype is a model that displays the appearance and behavior of an application or product early in the development lifecycle. 341 prototype-based programming codingscripting, glossary prototype-based programming is a style of object-oriented programming in which classes are not explicitly defined, but rather derived by adding properties and methods to an instance of another class or, less frequently, adding them to an empty object. in simple words: this type of style allows the creation of an object without first definin...

Index - Learn web development
learn, oojs, object-oriented, objects, l10n:priority in this assessment, you are expected to use the bouncing balls demo from the previous article as a starting point, and add some new and interesting features to it. 66 inheritance in javascript article, beginner, codingscripting, constructor, function, getter, inheritance, javascript, learn, oojs, oop, object, object member, prototype, extends, l10n:priority, setter this article has covered the remainder of the core oojs theory and syntax that we think you should know now. at this point you should understand javascript object and oop basics, prototypes and prototypal inheritance, how to create classes (constructors) and object instances, add features to classes, and create subclasses that inherit from other classes. ...
...ng practice article, beginner, canvas, codingscripting, guide, javascript, learn, objects, tutorial, l10n:priority we hope you had fun writing your own real world random bouncing balls example, using various object and object-oriented techniques from throughout the module! this should have given you some useful practice in using objects, and good real world context. ...
...l, l10n:priority we hope you had fun writing your own real world random bouncing balls example, using various object and object-oriented techniques from throughout the module! this should have given you some useful practice in using objects, and good real world context. 69 object prototypes article, beginner, codingscripting, constructor, javascript, learn, oojs, oop, object, prototype, prototype chaining, create(), l10n:priority this article has covered javascript object prototypes, including how prototype object chains allow objects to inherit features from one another, the prototype property and how it can be used to add methods to constructors, and other related topics. 70 object-oriented javascript for beginners article, beginner, codingscripting, cons...
...cript, learn, objects, test your skills this aim of this skill test is to assess whether you've understood our javascript object basics article. 73 test your skills: object-oriented javascript beginner, javascript, learn, oojs, objects, test your skills the aim of this skill test is to assess whether you've understood our object-oriented javascript for beginners, object prototypes, and inheritance in javascript articles. 74 working with json article, beginner, codingscripting, guide, json, json api, json arrays, json parsing, json structure, javascript, learn, objects, tutorial, l10n:priority in this article, we've given you a simple guide to using json in your programs, including how to create and parse json, and how to access data locked inside it. ...

Adding features to our bouncing balls demo - Learn web development
exists, which is used to track whether the balls exist in the program (have not been eaten by the evil circle). this should be a boolean (true/false). the ball() constructor should inherit the x, y, velx, vely, and exists properties from the shape() constructor. it should also define a color and a size property, like the original ball() constructor did. remember to set the ball() constructor's prototype and constructor appropriately. the ball draw(), update(), and collisiondetect() method definitions should be able to stay exactly the same as they were before. you also need to add a new parameter to the new ball() ( ... ) constructor call — the exists parameter should be the 5th parameter, and should be given a value of true. at this point, try reloading the code — it should work just th...
...ment. the evilcircle() constructor should inherit x, y, velx, vely, and exists from shape(), but velx and vely should always equal 20. you should do this something like shape.call(this, x, y, 20, 20, exists); it should also define its own properties, as follows: color — 'white' size — 10 again, remember to define your inherited properties as parameters in the constructor, and set the prototype and constructor properties correctly. defining evilcircle()'s methods evilcircle() should have four methods, as described below. draw() this method has the same purpose as ball()'s draw() method: it draws the object instance on the canvas. it will work in a very similar way, so you can start by copying the ball.prototype.draw definition. you should then make the following changes: we want ...
...u can see the evil circle a bit more easily. this can be achieved by setting a value for linewidth somewhere after the beginpath() call (3 will do). checkbounds() this method will do the same thing as the first part of ball()'s update() function — look to see whether the evil circle is going to go off the edge of the screen, and stop it from doing so. again, you can mostly just copy the ball.prototype.update definition, but there are a few changes you should make: get rid of the last two lines — we don't want to automatically update the evil circle's position on every frame, because we will be moving it in some other way, as you'll see below. inside the if() statements, if the tests return true we don't want to update velx/vely; we want to instead change the value of x/y so the evil circ...
...n online shareable editor (as mentioned in step 1 above). ...

How to implement a custom autocomplete search component
am {array.<string>|null=} comments */ function providerautocompleteresult(searchstring, searchresult, defaultindex, errordescription, results, comments) { this._searchstring = searchstring; this._searchresult = searchresult; this._defaultindex = defaultindex; this._errordescription = errordescription; this._results = results; this._comments = comments; } providerautocompleteresult.prototype = { _searchstring: "", _searchresult: 0, _defaultindex: 0, _errordescription: "", _results: [], _comments: [], /** * @return {string} the original search string */ get searchstring() { return this._searchstring; }, /** * @return {number} the result code of this result object, either: * result_ignored (invalid searchstring) * result_failure (failure...
..., removefromdb) { this._results.splice(index, 1); if (this._comments) this._comments.splice(index, 1); }, getlabelat: function(index) { return this._results[index]; }, queryinterface: xpcomutils.generateqi([ ci.nsiautocompleteresult ]) }; /** * @constructor * * @implements {nsiautocompletesearch} */ function providerautocompletesearch() { } providerautocompletesearch.prototype = { classid: class_id, classdescription : class_name, contractid : contract_id, /** * searches for a given string and notifies a listener (either synchronously * or asynchronously) of the result * * @param searchstring the string to search for * @param searchparam an extra parameter * @param previousresult a previous result to use for faster searchinig * @param list...
...leteresult(searchstring, searchresult, defaultindex, errordescription, results, comments) { this._searchstring = searchstring; this._searchresult = searchresult; this._defaultindex = defaultindex; this._errordescription = errordescription; this._results = results; this._comments = comments; } simpleautocompleteresult.prototype = { _searchstring: "", _searchresult: 0, _defaultindex: 0, _errordescription: "", _results: [], _comments: [], /** * the original search string */ get searchstring() { return this._searchstring; }, /** * the result code of this result object, either: * result_ignored (invalid searchstring) * result_failure (failure) * result_...
...ndex, removefromdb) { this._results.splice(index, 1); this._comments.splice(index, 1); }, queryinterface: function(aiid) { if (!aiid.equals(ci.nsiautocompleteresult) && !aiid.equals(ci.nsisupports)) throw components.results.ns_error_no_interface; return this; } }; // implements nsiautocompletesearch function simpleautocompletesearch() { } simpleautocompletesearch.prototype = { /* * search for a given string and notify a listener (either synchronously * or asynchronously) of the result * * @param searchstring - the string to search for * @param searchparam - an extra parameter * @param previousresult - a previous result to use for faster searchinig * @param listener - a listener to notify when the search is complete */ startsearch: functi...

sslfnc.html
t up by ssl_authcertificatehook is called to authenticate an incoming certificate. if the checksig parameter is set to pr_true, the callback function also verifies the digital signature. note: if you do not call ssl_authcertificatehook to supply a certificate authentication callback function, ssl uses the default callback function, ssl_authcertificate. the callback function has the following prototype: typedef secstatus (*sslauthcertificate) ( void *arg, prfiledesc *fd, prbool checksig, prbool isserver); this callback function has the following parameters: arg a pointer supplied by the application (in the call to ssl_authcertificatehook) that can be used to pass state information. can be null. fd a pointer to the file...
...ficate callback function gives the program an opportunity to do something (for example, log the attempt or authorize the certificate) when certificate authentication is not successful. if such a callback function is not provided by the application, the ssl connection simply fails when certificate authentication is not successful. the callback function set up by ssl_badcerthook has the following prototype: typedef secstatus (*sslbadcerthandler)( void *arg, prfiledesc *fd); this callback function has the following parameters: arg the arg parameter passed to ssl_badcerthook. fd a pointer to the file descriptor for the ssl socket. the callback function returns one of these values: secsuccess: the callback has cho...
...d by the server. the callback function retrieves the client's private key and certificate. ssl provides an implementation of this callback function; see nss_getclientauthdata for details. unlike ssl_authcertificate, nss_getclientauthdata is not a default callback function. you must set it explicitly with ssl_getclientauthdatahook if you want to use it. the callback function has the following prototype: typedef secstatus (*sslgetclientauthdata)( void *arg, prfiledesc *fd, certdistnames *canames, certcertificate **pretcert, seckeyprivatekey **pretkey); this callback function has the following parameters: arg the arg parameter passed to ssl_getclientauthdatahook. fd a pointer to the file descriptor for the ssl socket...
.... client_data a pointer to the value of the client_data argument that was passed to ssl_handshakecallback. returns the function returns one of these values: if successful, secsuccess. if unsuccessful, secfailure. use pr_geterror to obtain the error code. description the callback function set by ssl_handshakecallback has the following prototype: typedef void (*sslhandshakecallback)( prfiledesc *fd, void *client_data); this callback function has the following parameters: fd a pointer to the file descriptor for the ssl socket. client_data a pointer supplied by the application that can be used to pass state information. can be null. see also ssl commun...

Rhino scopes and contexts
expensive method to call and it allocates a fair amount of memory. we'll see below that there are ways to share a scope created this way among multiple scopes and threads. name lookup so how are scopes used to look up names? in general, variables are looked up by starting at the current variable object (which is different depending on what code is being executed in the program), traversing its prototype chain, and then traversing the parent chain. in the diagram below, the order in which the six objects are traversed is indicated. order of lookups in a two-deep scope chain with prototypes. for a more concrete example, let's consider the following script: var g = 7; function f(a) { var v = 8; x = v + a; } f(6); we have a top-level variable g, and the call to f will create a new top-l...
...n is traversed looking for a 'x' property. when none is found, a new property 'x' is created in the top-level scope. sharing scopes javascript is a language that uses delegation rather than traditional class-based inheritance. this is a large topic in itself, but for our purposes it gives us an easy way to share a set of read-only variables across multiple scopes. to do this we set an object's prototype. when accessing a property of an object in javascript, the object is first searched for a property with the given name. if none is found, the object's prototype is searched. this continues until either the object is found or the end of the prototype chain is reached. so to share information across multiple scopes, we first create the object we wish to share. typically this object will have been ...
...pe is searched. this continues until either the object is found or the end of the prototype chain is reached. so to share information across multiple scopes, we first create the object we wish to share. typically this object will have been created with initstandardobjects and may also have additional objects specific to the embedding. then all we need to do is create a new object and call its setprototypemethod to set the prototype to the shared object, and the parent of the new scope to null: scriptable newscope = cx.newobject(sharedscope); newscope.setprototype(sharedscope); newscope.setparentscope(null); the call to newobject simply creates a new javascript object with no properties. it uses thesharedscope passed in to initialize the prototype with the standard object.prototype value. we ca...
...ess to when it references a variable? the answer to 1 determines which scope should be the ultimate parent scope: rhino follows the parent chain up to the top and places the variable there. after you've constructed your parent scope chain, the answer to question 2 may indicate that there are additional scopes that need to be searched that are not in your parent scope chain. you can add these as prototypes of scopes in your parent scope chain. when rhino looks up a variable, it starts in the current scope, walks the prototype chain, then goes to the parent scope and its prototype chain, until there are no more parent scopes left. ...

JSAPI Cookbook
ropfunc, enumerable: true}); in the jsapi version, to signify that the property is read-only, pass null for the setter. ...
...n the jsapi version, to signify that the property is read-only, pass null for the setter. /* jsapi */ if (!js_defineproperty(cx, obj, "prop", js::undefinedvalue(), getpropfunc, null, jsprop_shared | jsprop_native_accessors | jsprop_enumerate)) { return false; } working with the prototype chain defining a native read-only property on the string.prototype // javascript object.defineproperty(string.prototype, "md5sum", {get: getmd5func, enumerable: true}); the following trick couldn't work if someone has replaced the global string object with something. /* jsapi */ jsobject *string; jsobject *string_prototype; js::value val; // get the string constructor from the global object. if (!js_getpro...
...laced the global string object with something. /* jsapi */ jsobject *string; jsobject *string_prototype; js::value val; // get the string constructor from the global object. if (!js_getproperty(cx, global, "string", &val)) return false; if (jsval_is_primitive(val)) return throwerror(cx, global, "string is not an object", __file__, __line__); string = jsval_to_object(val); // get string.prototype. if (!js_getproperty(cx, string, "prototype", &val)) return false; if (jsval_is_primitive(val)) return throwerror(cx, global, "string.prototype is not an object", __file__, __line__); string_prototype = jsval_to_object(val); // ...and now we can add some new functionality to all strings. ...
... actually outputting errors. how to write your own jsclass with reserved slots. ...

JS::IdentifyStandardInstance
this article covers features introduced in spidermonkey 31 determine if the given object is an instance/prototype/constructor for a standard class. syntax jsprotokey js::identifystandardinstance(jsobject *obj); jsprotokey js::identifystandardprototype(jsobject *obj); jsprotokey js::identifystandardinstanceorprototype(jsobject *obj); jsprotokey js::identifystandardconstructor(jsobject *obj); // added in spidermonkey 38 name type description obj jsobject * pointer to the instance/prototype/constructor object to determine. description js::identifystandardinstance determines if the given object is an instance for a standard class. ...
...constructor(jsobject *obj); // added in spidermonkey 38 name type description obj jsobject * pointer to the instance/prototype/constructor object to determine. description js::identifystandardinstance determines if the given object is an instance for a standard class. if so, return the associated jsprotokey. if not, return jsproto_null. js::identifystandardprototype determines if the given object is a prototype for a standard class. if so, return the associated jsprotokey. if not, return jsproto_null. js::identifystandardinstanceorprototype determines if the given object is an instance or prototype for a standard class. if so, return the associated jsprotokey. if not, return jsproto_null. js::identifystandardconstructor determines if the given object is a ...
... object is an instance or prototype for a standard class. if so, return the associated jsprotokey. if not, return jsproto_null. js::identifystandardconstructor determines if the given object is a constructor for a standard class. if so, return the associated jsprotokey. if not, return jsproto_null. ...
...f so, return the associated jsprotokey. if not, return jsproto_null. js::identifystandardconstructor determines if the given object is a constructor for a standard class. if so, return the associated jsprotokey. ...

JSClass.flags
, but in spidermonkey the global object is the last object in the scope chain, which can be different objects at different times. this is actually quite subtle. js_executescript and similar apis set the global object for the code they execute. ...
...milar apis set the global object for the code they execute. js_setglobalobject sets an object which is sometimes used as the global object, as a last resort.) enable standard ecmascript behavior for setting the prototype of certain objects, such as function objects. if the global object does not have this flag, then scripts may cause nonstandard behavior by replacing standard constructors or prototypes (such as function.prototype.) objects that can end up with the wrong prototype object, if this flag is not present, include: arguments objects (ecma 262-3 §10.1.8 specifies "the original object prototype"), function objects (ecma 262-3 §13.2 specifies "the original function prototype"), and objects created by many standard constructors (ecma 262-3 §15.4.2.1 and others). mxr id searc...
...'s resolve hook is actually a jsnewresolveop, not a jsresolveop. jsclass_share_all_properties obsolete since javascript 1.8.5 instructs spidermonkey to automatically give all properties of objects of this class the jsprop_shared attribute. jsclass_new_resolve_gets_start obsolete since jsapi 16 the resolve hook expects to receive the starting object in the prototype chain passed in via the *objp in/out parameter. (this is meaningful only if the jsclass_new_resolve flag is also set.) jsclass_construct_prototype obsolete since jsapi 11 instructs js_initclass to invoke the constructor when creating the class prototype. jsclass_is_extended obsolete since jsapi 17indicates that this jsclass is really a jsextendedclass. ...
...its internal use. they are jsclass_is_anonymous, jsclass_is_global, jsclass_is_proxy, and jsclass_has_cached_proto. jsapi applications should not use these flags. ...

Shell global objects
w scripts or out-of-memory) and return 'terminated' element if present with value v, convert v to an object o and mark the source as being attached to the dom element o. if the property is omitted or v is null, don't attribute the source to any dom element. elementattributename if present and not undefined, the name of property of element that holds this code. this is what debugger.source.prototype.elementattributename returns. sourcemapurl if present with value v, convert v to a string, and provide that as the code's source map url. if omitted, attach no source map url to the code (although the code may provide one itself, via a //#sourcemappingurl comment). sourceislazy if present and true, indicates that, after compilation, script source should not be cached by the js engine and ...
...ing column number for error messages and debug info element if present with value v, convert v to an object o and mark the source as being attached to the dom element o. if the property is omitted or v is null, don't attribute the source to any dom element. elementattributename if present and not undefined, the name of property of element that holds this code. this is what debugger.source.prototype.elementattributename returns. runoffthreadscript() wait for off-thread compilation to complete. if an error occurred, throw the appropriate exception; otherwise, run the script and return its value. offthreadcompilemodule(code) compile code on a helper thread. to wait for the compilation to finish and get the module object, call finishoffthreadmodule. finishoffthreadmodule() wait for of...
...trieve the source code for compilations that occurred long before it was set, and that it knows nothing about. the reverse applies as well: the original hook, that we reinstate after the call to fun completes, might be asked for the source code of compilations that fun performed, and which, presumably, only hook knows how to find. wrapwithproto(obj) wrap an object into a noop wrapper with prototype semantics. note: this is not fuzzing safe because it can be used to construct deeply nested wrapper chains that cannot exist in the wild. trackedopts(fun) returns an object describing the tracked optimizations of fun, if any. if fun is not a scripted function or has not been compiled by ion, null is returned. dumpscopechain(obj) prints the scope chain of an interpreted function or a module. ...
...olean properties options.args - show arguments to each function options.locals - show local variables in each frame options.thisprops - show the properties of the this object of each frame bytesize(value) return the size in bytes occupied by value, or undefined if value is not allocated in memory. bytesizeofscript(f) return the size in bytes occupied by the function f's jsscript. setimmutableprototype(obj) try to make obj's [[prototype]] immutable, such that subsequent attempts to change it will fail. return true if obj's [[prototype]] was successfully made immutable (or if it already was immutable), false otherwise. throws in case of internal error, or if the operation doesn't even make sense (for example, because the object is a revoked proxy). setlazyparsingdisabled(bool) explicitly disa...

XPCOM changes in Gecko 2.0
5-a4d2-3d4bde0f7ef8} category profile-after-change mycomponent @foobar/mycomponent;1 the javascript code no longer exports a nsgetmodule() function. it now must export a nsgetfactory() function, which accepts a class id (cid) as a parameter. ...
...sm"); function mycomponent() { } mycomponent.prototype = { // this must match whatever is in chrome.manifest! classid: components.id("{e6b866e3-41b2-4f05-a4d2-3d4bde0f7ef8}"), queryinterface: xpcomutils.generateqi([components.interfaces.nsimycomponent]), /* nsimycomponent implementation goes here */ ... }; // the following line is what xpcom uses to create components. each component prototype // must have a .classid which is used to create it. const nsgetfactory = xpcomutils.generatensgetfactory([mycomponent]); a component may implement backwards compatibility with gecko 1.9.2 by dynamically detecting which symbols are exported by xpcomutils.jsm and exporting the correct function: /** * xpcomutils.generatensgetfactory was introduced in mozilla 2 (firefox 4, seamonkey 2.1). * xpcomuti...
...en migrating to chrome.manifest. changed category names the xpcom category manager is used to register certain global helper objects. because chrome.manifest is a space-delimited format, category names with spaces cannot be registered. ...
...ory names the xpcom category manager is used to register certain global helper objects. because chrome.manifest is a space-delimited format, category names with spaces cannot be registered. ...

nsIHttpHeaderVisitor
ce in javascript and uses it to evaluate the mime type of a http response. this is done by subscribing to the http-on-examine-response and http-on-examine-cached-response observers. when the observer fires, the visitor interface is used to walk through the response headers and evaluate the mime type. ...
...valuate the mime type. ...
...totype.isflash = function ( ) { return this._isflash; }; myhttprequestobserver = function ( ) { this.register( ); this.aborted = components.results.ns_binding_aborted; this.nsihttpchannel = components.interfaces.nsihttpchannel; this.nsichannel = components.interfaces.nsichannel; this.nsirequest = components.interfaces.nsirequest; }; myhttprequestobserver.prototype.observe = function ( subject, topic, data ) { var uri, avisitor; if ( subject instanceof this.nsihttpchannel ) { avisitor = new mynsihttpheadervisitor( ); subject.visitresponseheaders( avisitor ); if ( avisitor.isflash( ) ) { uri = subject.uri; subject.cancel( this.aborted ); alert( "found flash!
... if ( subject instanceof this.nsihttpchannel ) { avisitor = new mynsihttpheadervisitor( ); subject.visitresponseheaders( avisitor ); if ( avisitor.isflash( ) ) { uri = subject.uri; subject.cancel( this.aborted ); alert( "found flash!" ); //handle flash file here } } }; myhttprequestobserver.prototype.register = function ( ) { var observerservice = components.classes[ "@mozilla.org/observer-service;1" ].getservice( components.interfaces.nsiobserverservice ); observerservice.addobserver(this, "http-on-examine-response", false); observerservice.addobserver(this, "http-on-examine-cached-response", false); }; myhttprequestobserver.prototype.unregister = function ( ) { ...

nsIXPCScriptable
constants constant value description want_precreate 1 << 0 want_create 1 << 1 want_postcreate 1 << 2 want_addproperty 1 << 3 want_delproperty 1 << 4 ...
...no implementor of this interface should ever return flags with this bit set. methods precreate() void precreate( in nsisupports nativeobj, ...
...no implementor of this interface should ever return flags with this bit set. methods precreate() void precreate( in nsisupports nativeobj, in jscontextptr cx, in jsobje...
...lse to indicate failure. newresolve() this method is called when the want_newresolve flag is set. when this method is called, xpconnect is attempting to resolve a lazy property named by id on obj. the js engine will check if the property named by id is defined after this method has been called. this is very similar to jsnewresolveop. if an implementation of this method throws an error code, the prototype chain will not be checked for the property. prbool newresolve( in nsixpconnectwrappednative wrapper, in jscontextptr cx, in jsobjectptr obj, in jsval id, in pruint32 flags, out jsobjectptr objp ); parameters wrapper cx the pointer to the jscontext newresolve is being called from. obj the pointer to the jsobject that the property named by id that is being accessed. id ...

Debugger - Firefox Developer Tools
the debugger object when called as a constructor, the debugger object creates a new debugger instance. new debugger([global, …]) create a debugger object, and apply its adddebuggee method to each of the givenglobal objects to add them as the initial debuggees. accessor properties of the debugger prototype object a debugger instance inherits the following accessor properties from its prototype: enabled a boolean value indicating whether this debugger instance’s handlers, breakpoints, and the like are currently enabled. it is an accessor property with a getter and setter: assigning to it enables or disables this debugger instance; reading it produces true if the instance is enabled, or false otherwise. this property is initially true in a freshly created debugger instance. ...
...lity-based restrictions on a debugger’s reach. however, the onnewglobalobject method allows the api user to monitor all global object creation that occurs anywhere within the javascript system (the “jsruntime”, in spidermonkey terms), thereby escaping the capability-based limits. for this reason, onnewglobalobject is only available to privileged code. function properties of the debugger prototype object the functions described below may only be called with a this value referring to a debugger instance; they may not be used as methods of other kinds of objects. adddebuggee(global) add the global object designated byglobal to the set of global objects this debugger instance is debugging. if the designated global is already a debuggee, this has no effect. return this debugger’s debu...
... objects are returned; an object must meet all the criteria given by query to be returned. if query is omitted, we return the debugger.object instances for all objects allocated in the scope of debuggee globals. the query object may have the following properties: class if present, only return objects whose internal [[class]]’s name matches the given string. note that in some cases, the prototype object for a given constructor has the same [[class]] as the instances that refer to it, but cannot itself be used as a valid instance of the class. code gathering objects by class name may need to examine them further before trying to use them. all properties of query are optional. passing an empty object returns all objects in debuggee globals. unlike findscripts, this function is determi...
...ased limits. for this reason, findallglobals is only available to privileged code. makeglobalobjectreference(global) return the debugger.object whose referent is the global object designated byglobal, without adding the designated global as a debuggee. ifglobal does not designate a global object, throw a typeerror. determine which global is designated byglobal using the same rules as debugger.prototype.adddebuggee. adoptdebuggeevalue(value) given a debuggee value value owned by an arbitrary debugger, return an equivalent debuggee value owned by this debugger. if value is a primitive value, return it unchanged. if value is a debugger.object owned by an arbitrary debugger, return an equivalent debugger.object owned by this debugger. otherwise, if value is some other kind of object, and henc...

Element.hasAttribute() - Web APIs
e() method returns a boolean value indicating whether the specified element has the specified attribute or not. syntax var result = element.hasattribute(name); result holds the return value true or false. name is a string representing the name of the attribute. ...
...s a boolean value indicating whether the specified element has the specified attribute or not. syntax var result = element.hasattribute(name); result holds the return value true or false. name is a string representing the name of the attribute. ...
...ing whether the specified element has the specified attribute or not. syntax var result = element.hasattribute(name); result holds the return value true or false. name is a string representing the name of the attribute. ...
...true or false. name is a string representing the name of the attribute. ...

Node.hasChildNodes() - Web APIs
nodes() method returns a boolean value indicating whether the given node has child nodes or not. syntax bool = node.haschildnodes(); return value a boolean that is true if the node has child nodes, and false otherwise. ...
...returns a boolean value indicating whether the given node has child nodes or not. syntax bool = node.haschildnodes(); return value a boolean that is true if the node has child nodes, and false otherwise. ...
...dicating whether the given node has child nodes or not. syntax bool = node.haschildnodes(); return value a boolean that is true if the node has child nodes, and false otherwise. ...
...ildnodes(); return value a boolean that is true if the node has child nodes, and false otherwise. example let foo = document.getelementbyid('foo'); if (foo.haschildnodes()) { // do something with 'foo.childnodes' } polyfill here is one possible polyfill: ;(function(prototype) { prototype.haschildnodes = prototype.haschildnodes || function() { return !!this.firstchild; } })(node.prototype); there are various ways to determine whether the node has a child node: node.haschildnodes() node.firstchild != null (or just node.firstchild) node.childnodes && node.childnodes.length (or node.childnodes.length > 0) specifications specification status comment domthe definition of 'node: haschildnodes' in that specification. living standard ...

ParentNode.children - Web APIs
nodes in the collection by using either the item() method on the collection, or by using javascript array-style notation. if the node has no element children, then children is an empty list with a length of 0. example const foo = document.getelementbyid('foo'); for (let i = 0; i < foo.children.length; i++) { console.log(foo.children[i].tagname); } polyfill // overwrites native 'children' prototype. ...
... empty list with a length of 0. example const foo = document.getelementbyid('foo'); for (let i = 0; i < foo.children.length; i++) { console.log(foo.children[i].tagname); } polyfill // overwrites native 'children' prototype. // adds document & documentfragment support for ie9 & safari. // returns array instead of htmlcollection. ...
...0. example const foo = document.getelementbyid('foo'); for (let i = 0; i < foo.children.length; i++) { console.log(foo.children[i].tagname); } polyfill // overwrites native 'children' prototype. // adds document & documentfragment support for ie9 & safari. // returns array instead of htmlcollection. ...
...= 0; i < foo.children.length; i++) { console.log(foo.children[i].tagname); } polyfill // overwrites native 'children' prototype. // adds document & documentfragment support for ie9 & safari. // returns array instead of htmlcollection. ...

ParentNode.firstElementChild - Web APIs
l change that shouldn't affect compatibility. syntax var element = node.firstelementchild; example <ul id="foo"> <li>first (1)</li> <li>second (2)</li> <li>third (3)</li> </ul> <script> var foo = document.getelementbyid('foo'); // yields: first (1) console.log(foo.firstelementchild.textcontent); </script> polyfill for ie8, ie9 and safari // overwrites native 'firstelementchild' prototype. ...
... <li>second (2)</li> <li>third (3)</li> </ul> <script> var foo = document.getelementbyid('foo'); // yields: first (1) console.log(foo.firstelementchild.textcontent); </script> polyfill for ie8, ie9 and safari // overwrites native 'firstelementchild' prototype. // adds document & documentfragment support for ie9 & safari. ...
... (3)</li> </ul> <script> var foo = document.getelementbyid('foo'); // yields: first (1) console.log(foo.firstelementchild.textcontent); </script> polyfill for ie8, ie9 and safari // overwrites native 'firstelementchild' prototype. // adds document & documentfragment support for ie9 & safari. ...
...rst (1) console.log(foo.firstelementchild.textcontent); </script> polyfill for ie8, ie9 and safari // overwrites native 'firstelementchild' prototype. // adds document & documentfragment support for ie9 & safari. ...

ParentNode.lastElementChild - Web APIs
hild example <ul id="foo"> <li>first (1)</li> <li>second (2)</li> <li>third (3)</li> </ul> <script> const foo = document.getelementbyid('foo'); console.log(foo.lastelementchild.textcontent); // logs: third (3) </script> polyfill the code below adds support of lastelementchild() to document and documentfragment in internet explorer and safari. // overwrites native 'lastelementchild' prototype. ...
...foo = document.getelementbyid('foo'); console.log(foo.lastelementchild.textcontent); // logs: third (3) </script> polyfill the code below adds support of lastelementchild() to document and documentfragment in internet explorer and safari. // overwrites native 'lastelementchild' prototype. // returns array instead of htmlcollection. ...
...('foo'); console.log(foo.lastelementchild.textcontent); // logs: third (3) </script> polyfill the code below adds support of lastelementchild() to document and documentfragment in internet explorer and safari. // overwrites native 'lastelementchild' prototype. // returns array instead of htmlcollection. ...
.../script> polyfill the code below adds support of lastelementchild() to document and documentfragment in internet explorer and safari. // overwrites native 'lastelementchild' prototype. // returns array instead of htmlcollection. ...

ARIA: grid role - Accessibility
tbody td[role="gridcell"]:hover, tbody td[role="gridcell"]:focus { background-color: #f6f6f6; outline: 3px solid blue; } } javascript var selectables = document.queryselectorall('table td[role="gridcell"]'); selectables[0].setattribute('tabindex', 0); var trs = document.queryselectorall('table tbody tr'), row = 0, col = 0, maxrow = trs.length - 1, maxcol = 0; array.prototype.foreach.call(trs, function(gridrow, i){ array.prototype.foreach.call(gridrow.queryselectorall('td'), function(el, i){ el.dataset.row = row; el.dataset.col = col; col = col + 1; }); if (col>maxcol) { maxcol = col - 1; } col = 0; row = row + 1; }); function moveto(newrow, newcol) { var tgt = document.queryselector('[data-row="' + newrow + '"][data-col="' + newcol + '"]'); ...
....call(gridrow.queryselectorall('td'), function(el, i){ el.dataset.row = row; el.dataset.col = col; col = col + 1; }); if (col>maxcol) { maxcol = col - 1; } col = 0; row = row + 1; }); function moveto(newrow, newcol) { var tgt = document.queryselector('[data-row="' + newrow + '"][data-col="' + newcol + '"]'); if (tgt && (tgt.getattribute('role')==='gridcell') ) { array.prototype.foreach.call(document.queryselectorall('[role=gridcell]'), function(el, i){ el.setattribute('tabindex', '-1'); }); tgt.setattribute('tabindex', '0'); tgt.focus(); return true; } else { return false; } } document.queryselector('table').addeventlistener("keydown", function(event) { switch (event.key) { case "arrowright": moveto(parseint(event.target.datase...
... #000; } tbody td[role="gridcell"]:hover, tbody td[role="gridcell"]:focus { background-color: #f6f6f6; outline: 3px solid blue; } javascript var selectables = document.queryselectorall('table td[role="gridcell"]'); selectables[0].setattribute('tabindex', 0); var trs = document.queryselectorall('table tbody tr'), row = 0, col = 0, maxrow = trs.length - 1, maxcol = 0; array.prototype.foreach.call(trs, function(gridrow, i){ array.prototype.foreach.call(gridrow.queryselectorall('td'), function(el, i){ el.dataset.row = row; el.dataset.col = col; col = col + 1; }); if (col>maxcol) { maxcol = col - 1; } col = 0; row = row + 1; }); function moveto(newrow, newcol) { var tgt = document.queryselector('[data-row="' + newrow + '"][data-col="' + newcol + '"]'); ...
....call(gridrow.queryselectorall('td'), function(el, i){ el.dataset.row = row; el.dataset.col = col; col = col + 1; }); if (col>maxcol) { maxcol = col - 1; } col = 0; row = row + 1; }); function moveto(newrow, newcol) { var tgt = document.queryselector('[data-row="' + newrow + '"][data-col="' + newcol + '"]'); if (tgt && (tgt.getattribute('role')==='gridcell') ) { array.prototype.foreach.call(document.queryselectorall('[role=gridcell]'), function(el, i){ el.setattribute('tabindex', '-1'); }); tgt.setattribute('tabindex', '0'); tgt.focus(); return true; } else { return false; } } document.queryselector('table').addeventlistener("keydown", function(event) { switch (event.key) { case "arrowright": moveto(parseint(event.target.datase...

Overview of events and handlers - Developer guides
easily be followed using completely custom code, as explained in the article on custom events. the pattern is also used by modern web browsers which define many events emitted in response to user input or browser activity. modern web browsers follow the event pattern using a standardized approach. browsers use as the data structure for the properties of the event, an object derived from the eventprototype object. browsers use as the registration method for the function which will handle those data structures a method called addeventlistener which expects as arguments a string event type name and the handler function. finally, browsers define a large number of objects as event emitters and define a wide variety of event types generated by the objects. button event handler demo for example, browse...
...ck' in response to a mouse click or, when displayed in touch sensitive surfaces, to a finger tap. ...
... mouse click or, when displayed in touch sensitive surfaces, to a finger tap. ...
...hed loading, the dom node objects such as div or button emit an event called 'click' when the user presses the mouse button while the mouse pointer is on top of the dom node in the html page. the event object hierarchy the web browser defines many events of different kinds. each definition includes, as the data structure passed to the handler function, an object which inherits from the eventprototype object. a partial diagram of the class hierarchy of event objects is: note: this diagram is incomplete. the web api documentation contains a page defining the event object which also includes the known dom event subclasses of the event object. documents three sources on the mdn (mozilla developer network) web site are particularly useful for programmers wanting to work with events: th...

Equality comparisons and sameness - JavaScript
which operation you choose depends on what sort of comparison you are looking to perform. briefly: double equals (==) w...
... which operation you choose depends on what sort of comparison you are looking to perform. briefly: double equals (==) w...
... which operation you choose depends on what sort of comparison you are looking to perform. briefly: double equals (==) w...
... which operation you choose depends on what sort of comparison you are looking to perform. briefly: double equals (==) w...

constructor - JavaScript
for the polygon's width and height super(length, length); // note: in derived classes, `super()` must be called before you // can use `this`. leaving this out will cause a referenceerror. ...
...ue**0.5; this.width = value**0.5; } } another example here the prototype of square class is changed—but the constructor of its base class polygon is still called when a new instance of a square is created. ...
...idth = value**0.5; } } another example here the prototype of square class is changed—but the constructor of its base class polygon is still called when a new instance of a square is created. ...
...} } another example here the prototype of square class is changed—but the constructor of its base class polygon is still called when a new instance of a square is created. class polygon { constructor() { this.name = "polygon"; } } class square extends polygon { constructor() { super(); } } class rectangle {} object.setprototypeof(square.prototype, rectangle.prototype); console.log(object.getprototypeof(square.prototype) === polygon.prototype); //false console.log(object.getprototypeof(square.prototype) === rectangle.prototype); //true let newinstance = new square(); console.log(newinstance.name); //polygon specifications specification ecmascript (ecma-262)the definition of 'constructor method' in that specification. ...

Intl.DateTimeFormat - JavaScript
ase clone https://github.com/mdn/interactive-examples and send us a pull request. constructor intl.datetimeformat() creates a new datetimeformat object. static methods intl.datetimeformat.supportedlocalesof() returns an array containing those of the provided locales that are supported without having to fall back to the runtime's default locale. ...
...t. static methods intl.datetimeformat.supportedlocalesof() returns an array containing those of the provided locales that are supported without having to fall back to the runtime's default locale. instance methods intl.datetimeformat.prototype.format() getter function that formats a date according to the locale and formatting options of this datetimeformat object. intl.datetimeformat.prototype.formattoparts() returns an array of objects representing the date string in parts that can be used for custom locale-aware formatting. ...
...ck to the runtime's default locale. instance methods intl.datetimeformat.prototype.format() getter function that formats a date according to the locale and formatting options of this datetimeformat object. intl.datetimeformat.prototype.formattoparts() returns an array of objects representing the date string in parts that can be used for custom locale-aware formatting. intl.datetimeformat.prototype.resolvedoptions() returns a new object with properties reflecting the locale and formatting options computed during initialization of the object. ...
...ns of this datetimeformat object. intl.datetimeformat.prototype.formattoparts() returns an array of objects representing the date string in parts that can be used for custom locale-aware formatting. intl.datetimeformat.prototype.resolvedoptions() returns a new object with properties reflecting the locale and formatting options computed during initialization of the object. intl.datetimeformat.prototype.formatrange() this method receives two dates and formats the date range in the most concise way based on the locale and options provided when instantiating datetimeformat. intl.datetimeformat.prototype.formatrangetoparts() this method receives two dates and returns an array of objects containing the locale-specific tokens representing each part of the formatted date range. examples using da...

Promise - JavaScript
alue, or rejected with a reason (error). when either of these options happens, the associated handlers queued up by a promise's then method are called. if the promise has already been fulfilled or rejected when a corresponding handler is attached, the handler will be called, so there is no race condition between an asynchronous operation completing and its handlers being attached. as the promise.prototype.then() and promise.prototype.catch() methods return promises, they can be chained. not to be confused with: several other languages have mechanisms for lazy evaluation and deferring a computation, which they also call "promises", e.g. scheme. promises in javascript represent processes that are already happening, which can be chained with callback functions. if you are looking to lazily evalua...
... resolved with the given value. if the value is a thenable (i.e. has a then method), the returned promise will "follow" that thenable, adopting its eventual state; otherwise the returned promise will be fulfilled with the value. generally, if you don't know if a value is a promise or not, promise.resolve(value) it instead and work with the return value as a promise. ...
...you don't know if a value is a promise or not, promise.resolve(value) it instead and work with the return value as a promise. instance methods promise.prototype.catch() appends a rejection handler callback to the promise, and returns a new promise resolving to the return value of the callback if it is called, or to its original fulfillment value if the promise is instead fulfilled. promise.prototype.then() appends fulfillment and rejection handlers to the promise, and returns a new promise resolving to the return value of the called handler, or to its original settled value if the promise was not handled (i.e. ...
...the handler is called when the promise is settled, whether fulfilled or rejected. ...

WebAssembly.CompileError - JavaScript
the webassembly.compileerror object indicates an error during webassembly decoding or validation. constructor webassembly.compileerror() creates a new webassembly.compileerror object. instance properties webassembly.compileerror.prototype.message error message. although ecma-262 specifies that urierror should provide its own message property, in spidermonkey, it inherits error.prototype.message. webassembly.compileerror.prototype.name error name. inherited from error. webassembly.compileerror.prototype.filename path to file that raised this error. inherited from error. webassembly.compileerror.prototype.linenumber line number in file that raised this error. inherited from error. webassembly.compileerror.prototype.columnnumber column number in line that raised this error. inherit...
...inherited from error. ...
...inherited from error. ...
...inherited from error. ...

WebAssembly.LinkError - JavaScript
the webassembly.linkerror object indicates an error during module instantiation (besides traps from the start function). constructor webassembly.linkerror() creates a new webassembly.linkerror object. instance properties webassembly.linkerror.prototype.message error message. although ecma-262 specifies that urierror should provide its own message property, in spidermonkey, it inherits error.prototype.message. webassembly.linkerror.prototype.name error name. inherited from error. webassembly.linkerror.prototype.filename path to file that raised this error. inherited from error. webassembly.linkerror.prototype.linenumber line number in file that raised this error. inherited from error. webassembly.linkerror.prototype.columnnumber column number in line that raised this error. inher...
...inherited from error. ...
...inherited from error. ...
...inherited from error. ...

WebAssembly.RuntimeError - JavaScript
the webassembly.runtimeerror object is the error type that is thrown whenever webassembly specifies a trap. constructor webassembly.runtimeerror() creates a new webassembly.runtimeerror object. instance properties webassembly.runtimeerror.prototype.message error message. although ecma-262 specifies that urierror should provide its own message property, in spidermonkey, it inherits error.prototype.message. webassembly.runtimeerror.prototype.name error name. inherited from error. ...
... webassembly.runtimeerror() creates a new webassembly.runtimeerror object. instance properties webassembly.runtimeerror.prototype.message error message. although ecma-262 specifies that urierror should provide its own message property, in spidermonkey, it inherits error.prototype.message. webassembly.runtimeerror.prototype.name error name. inherited from error. webassembly.runtimeerror.prototype.filename path to file that raised this error. inherited from error. webassembly.runtimeerror.prototype.linenumber line number in file that raised this error. inherited from error. webassembly.runtimeerror.prototype.columnnumber column number in line that raised this error. inherited from error. webassembly.runtimeerror.prototype.stack stack trace. inherited from error. instance methods ...
...inherited from error. ...
...inherited from error. ...

delete operator - JavaScript
page for more details. the delete operator removes a given property from an object. on successful deletion, it will return true, else false will be returned. however, it is important to consider the following scenarios: if the property which you are trying to delete does not exist, delete will not have any effect and will return true. if a property with the same name exists on the object's prototype chain, then, after deletion, the object will use the property from the prototype chain (in other words, delete only has an effect on own properties). any property declared with var cannot be deleted from the global scope or from a function's scope. as such, delete cannot delete any functions in the global scope (whether this is part from a function definition or a function expression). fun...
...ram) { // syntaxerror in strict mode. console.log(delete param); // false } // syntaxerror in strict mode. console.log(delete func); // false cross-browser notes although ecmascript makes iteration order of objects implementation-dependent, it may appear that all major browsers support an iteration order based on the earliest added property coming first (at least for properties not on the prototype). however, in the case of internet explorer, when one uses delete on a property, some confusing behavior results, preventing other browsers from using simple objects like object literals as ordered associative arrays. in explorer, while the property value is indeed set to undefined, if one later adds back a property with the same name, the property will be iterated in its old position--not at the...
...; // returns true // delete does not affect built-in static properties. delete math.pi; // returns false // employeedetails is a property of the global scope. // since it was defined without "var", it is marked configurable. delete employeedetails; // returns true function f() { var z = 44; // delete doesn't affect local variable names delete z; // returns false } delete and the prototype chain in the following example, we delete an own property of an object while a property with the same name is available on the prototype chain: function foo() { this.bar = 10; } foo.prototype.bar = 42; var foo = new foo(); // foo.bar is associated with the // own property. console.log(foo.bar); // 10 // delete the own property within the // foo object. delete foo.bar; // returns true // ...
...delete an own property of an object while a property with the same name is available on the prototype chain: function foo() { this.bar = 10; } foo.prototype.bar = 42; var foo = new foo(); // foo.bar is associated with the // own property. console.log(foo.bar); // 10 // delete the own property within the // foo object. delete foo.bar; // returns true // foo.bar is still available in the // prototype chain. console.log(foo.bar); // 42 // delete the property on the prototype. delete foo.prototype.bar; // returns true // the "bar" property can no longer be // inherited from foo since it has been // deleted. console.log(foo.bar); // undefined deleting array elements when you delete an array element, the array length is not affected. this holds even if you delete the last element of the array...

new operator - JavaScript
define the object type by writing a function. create an instance of the object with new. to define an object type, create a function for the object type that specifies its name and properties. an object can have a property that is itself another object. see the examples below. when the code new foo(...) is executed, the following things happen: a new object is created, inheriting from foo.prototype. the constructor function foo is called with the specified arguments, and with this bound to the newly created object. new foo is equivalent to new foo(), i.e. if no argument list is specified, foo is called without arguments. the object (not null, false, 3.1415 or other primitive types) returned by the constructor function becomes the result of the whole new expression. if the constructor func...
...iously defined object. for example, the statement car1.color = "black" adds a property color to car1, and assigns it a value of "black". however, this does not affect any other objects. to add the new property to all objects of the same type, you must add the property to the definition of the car object type. you can add a shared property to a previously defined object type by using the function.prototype property. this defines a property that is shared by all objects created with that function, rather than by just one instance of the object type. the following code adds a color property with value "original color" to all objects of type car, and then overwrites that value with the string "black" only in the instance object car1. for more information, see prototype. function car() {} car1 = new c...
...d with that function, rather than by just one instance of the object type. the following code adds a color property with value "original color" to all objects of type car, and then overwrites that value with the string "black" only in the instance object car1. for more information, see prototype. ...
...r, and then overwrites that value with the string "black" only in the instance object car1. for more information, see prototype. function car() {} car1 = new car(); car2 = new car(); console.log(car1.color); // undefined car.prototype.color = 'original color'; console.log(car1.color); // 'original color' car1.color = 'black'; console.log(car1.color); // 'black' console.log(object.getprototypeof(car1).color); // 'original color' console.log(object.getprototypeof(car2).color); // 'original color' console.log(car1.color); // 'black' console.log(car2.color); // 'original color' if you didn't write the new operator, the constructor function would be invoked like any regular function, without creating an object. in this case, the value of this is also different. examples object ty...

this - JavaScript
ct. to set the value of this to a particular value when calling a function, use call(), or apply() as in the examples below. class context the behavior of this in classes and functions is similar, since classes are functions under the hood. but there are some differences and caveats. within a class constructor, this is a regular object. all non-static methods within the class are added to the prototype of this: class example { constructor() { const proto = object.getprototypeof(this); console.log(object.getownpropertynames(proto)); } first(){} second(){} static third(){} } new example(); // ['constructor', 'first', 'second'] note: static methods are not properties of this. they are properties of the class itself. derived classes unlike base class constructors, derived ...
...as this is not an object, an attempt will be made to convert it to an object. values null and undefined become the global object. primitives like 7 or 'foo' will be converted to an object using the related constructor, so the primitive number 7 is converted to an object as if by new number(7) and the string 'foo' to an object as if by new string('foo'), e.g. function bar() { console.log(object.prototype.tostring.call(this)); } bar.call(7); // [object number] bar.call('foo'); // [object string] bar.call(undefined); // [object global] the bind method ecmascript 5 introduced function.prototype.bind(). calling f.bind(someobject) creates a new function with the same body and scope as f, but where this occurs in the original function, in the new function it is permanently bound to the first ar...
...diate member reference. in the following example, when we invoke the function, we call it as a method g of the object o.b. this time during execution, this inside the function will refer to o.b. the fact that the object is itself a member of o has no consequence; the most immediate reference is all that matters. o.b = {g: independent, prop: 42}; console.log(o.b.g()); // 42 this on the object's prototype chain the same notion holds true for methods defined somewhere on the object's prototype chain. if the method is on an object's prototype chain, this refers to the object the method was called on, as if the method were on the object. var o = {f: function() { return this.a + this.b; }}; var p = object.create(o); p.a = 1; p.b = 4; console.log(p.f()); // 5 in this example, the object assigned t...
...ject's prototype chain. if the method is on an object's prototype chain, this refers to the object the method was called on, as if the method were on the object. var o = {f: function() { return this.a + this.b; }}; var p = object.create(o); p.a = 1; p.b = 4; console.log(p.f()); // 5 in this example, the object assigned to the variable p doesn't have its own f property, it inherits it from its prototype. but it doesn't matter that the lookup for f eventually finds a member with that name on o; the lookup began as a reference to p.f, so this inside the function takes the value of the object referred to as p. that is, since f is called as a method of p, its this refers to p. this is an interesting feature of javascript's prototype inheritance. this with a getter or setter again, the same notion ...

Preferences - Archive of obsolete content
{ // keeping a reference to the observed preference branch or it will get // garbage collected. ...
...ame); this._branch.queryinterface(components.interfaces.nsiprefbranch2); this._callback = callback; } preflistener.prototype.observe = function(subject, topic, data) { if (topic == 'nspref:changed') this._callback(this._branch, data); }; /** * @param {boolean=} trigger if true triggers the registered function * on registration, that is, when this method is called. */ preflistener.prototype.register = function(trigger) { this._branch.addobserver('', this, false); if (trigger) { let that = this; this._branch.getchildlist('', {}). ...
...f true triggers the registered function * on registration, that is, when this method is called. */ preflistener.prototype.register = function(trigger) { this._branch.addobserver('', this, false); if (trigger) { let that = this; this._branch.getchildlist('', {}). ...

Offering a context menu for form controls - Archive of obsolete content
xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"> <script type="application/javascript" src="chrome://formcontrolcontextmenu/content/overlay.js"/> </overlay> change the right-click behavior the overlaid code is responsible for adjusting the behavior of right-clicking on form controls. ...
...cation/javascript" src="chrome://formcontrolcontextmenu/content/overlay.js"/> </overlay> change the right-click behavior the overlaid code is responsible for adjusting the behavior of right-clicking on form controls. ...
...arget; components.utils.reporterror(settargetoriginal); nscontextmenu.prototype.settarget = function(anode, arangeparent, arangeoffset) { settargetoriginal.apply(this, arguments); if (this.istargetaformcontrol(anode)) this.shoulddisplay = true; }; }, false); this code, which is run when the window is opened up, works by replacing the settarget() routine for the prototype of nscontextmenu with one that forces the context menu to display if the target of the menu is a form control. as a result, all controls in the window will support a context menu when right-clicked, since we've changed the core behavior of context menus to override their default behavior of doing nothing on form controls. ...

Promises - Archive of obsolete content
// path, at 1000ms minimum intervals. this.saver = new deferredsave(this.path, () => json.stringify(this.data), 1000); return this; }.bind(this)); } /** * immediately save the data to disk. * * @return {promise} a promise which resolves when the file's contents * have been written. ...
...omise} a promise which resolves when the file's contents * have been written. */ jsonstore.prototype.flush = function () { return this.saver.flush(); }; /** * queue a save operation. the operation will commence after a full * second has passed without further calls to this method. * * @return {promise} a promise which resolves when the file's contents * have been written. ...
...mimetype) xhr.overridemimetype(params.options); xhr.open(options.method || defaultmethod, url); if (options.responsetype) xhr.responsetype = options.responsetype; for (let header of object.keys(options.headers || {})) xhr.setrequestheader(header, options.headers[header]); let data = options.data; if (data && object.getprototypeof(data).constructor.name == "object") { options.data = new formdata; for (let key of object.keys(data)) options.data.append(key, data[key]); } xhr.send(options.data); }); } example usage: task.spawn(function* () { let request = yield request("http://example.com/", { method: "put", mimetype: "application/json", ...

How to implement a custom XUL query processor component - Archive of obsolete content
?name=xxx", where the xxx is the querytype used in the xul template block. ...
...urn null; }, // called when a rule matches this item. ...
... function templatequeryprocessor() { // our basic list of data this._data = [ {name: "mark", age: 36, hair: "brown", eye: "brown"}, {name: "bill", age: 25, hair: "red", eye: "black"}, {name: "joe", age: 15, hair: "blond", eye: "blue"}, {name: "jimmy", age: 65, hair: "gray", eye: "dull"} ]; } templatequeryprocessor.prototype = { queryinterface: xpcomutils.generateqi([components.interfaces.nsixultemplatequeryprocessor]), classdescription: "sample xul template query processor", classid: components.id("{282cc4ea-a49c-44fc-81f4-1f03cbb7825f}"), contractid: "@mozilla.org/xul/xul-query-processor;1?name=simpledata", getdatasource: function(adatasources, arootnode, aistrusted, abuilder, ashoulddelaybuilding) { ...

Object-oriented JavaScript for beginners - Learn web development
1 and person2 variables contain the following objects: { name: 'bob', greeting: function() { alert('hi! i\'m ' + this.name + '.'); } } { name: 'sarah', greeting: function() { alert('hi! i\'m ' + this.name + '.'); } } note that when we are calling our constructor function, we are defining greeting() every time, which isn't ideal. to avoid this, we can define functions on the prototype instead, which we will look at later. creating our finished constructor the example we looked at above was only a simple example to get us started. let's now get on and create our final person() constructor function. remove the code you inserted so far, and add in this replacement constructor — this is exactly the same as the simple example in principle, with just a bit more complexity: ...
...n the next two articles, so you might want to read them first before you try the tests. summary this article has provided a simplified view of object-oriented theory — this isn't the whole story, but it gives you an idea of what we are dealing with here. ...
... view of object-oriented theory — this isn't the whole story, but it gives you an idea of what we are dealing with here. in addition, we have started to look at different ways of generating object instances. in the next article, we'll explore javascript object prototypes. ...

React interactivity: Editing, filtering, conditional rendering - Learn web development
app. editing the name of a task we don’t have a user interface for editing the name of a task yet. we'll get to that in a moment. to start with, we can at least implement an edittask() function in app.js. it’ll be similar to deletetask() because it'll take an id to find its target object, but it'll also take a newname property containing the name to update the task to. we'll use array.prototype.map() instead of array.prototype.filter() because we want to return a new array with some changes, instead of deleting something from the array. add the edittask() function inside your app component, in the same place as the other functions: function edittask(id, newname) { const editedtasklist = tasks.map(task => { // if this task has the same id as the edited task if (id === task.id) ...
...n't actually filter the todos in the ui! let's finish this off. filtering tasks in the ui right now, our tasklist constant in app() maps over the tasks state and returns a new <todo /> component for all of them. this is not what we want! a task should only render if it is included in the results of applying the selected filter. before we map over the tasks state, we should filter it (with array.prototype.filter()) to eliminate objects we don't want to render. update your tasklist like so: const tasklist = tasks .filter(filter_map[filter]) .map(task => ( <todo id={task.id} name={task.name} completed={task.completed} key={task.id} toggletaskcompleted={toggletaskcompleted} deletetask={deletetask} edittask={edittask} /> )); in order to decide...
...want to render. update your tasklist like so: const tasklist = tasks .filter(filter_map[filter]) .map(task => ( <todo id={task.id} name={task.name} completed={task.completed} key={task.id} toggletaskcompleted={toggletaskcompleted} deletetask={deletetask} edittask={edittask} /> )); in order to decide which callback function to use in array.prototype.filter(), we access the value in filter_map that corresponds to the key of our filter state. when filter is all, for example, filter_map[filter] will evaluate to () => true. choosing a filter in your browser will now remove the tasks that do not meet its criteria. the count in the heading above the list will also change to reflect the list! summary so that's it — our app is now functionall...

Displaying Places information using views
treeview"); treeview.selectplaceuri("some place uri"); to select a row in the tree that contains a specific nsinavhistoryresultnode: var treeview = document.getelementbyid("myplacestreeview"); treeview.selectnode(somehistoryresultnode); placestreeview note: this section describes the implementation of the places tree view. the built-in tree view is backed by an instance of placestreeview, a prototype defined in browser/components/places/content/treeview.js. placestreeview performs double duty for the built-in tree view: it implements both nsitreeview and much of the functionality required of a places view. the latter functionality is specified specifically by interface nsinavhistoryresulttreeviewer, which inherits from the more general nsinavhistoryresultobserver . because of placestreeview'...
...ook at using the tree view above to get an idea of what's required. custom nsitreeviews in general are a lot of work, and if you are not familiar with creating custom nsitreeviews, see the custom tree views and tree view details pages in the xul tutorial. all of that information is relevant here. fortunately you can commandeer parts of the built-in tree view to suit your purposes. the javascript prototype backing the built-in view, placestreeview, is especially useful since it implements all three of nsinavhistoryresulttreeviewer, nsinavhistoryresultobserver, and nsitreeview. you can therefore implement your own custom functionality on top of placestreeview while relying on it for non-custom functionality and much of the tedious work. one strategy is to create your custom object(s) implementing ea...
...nvenience properties or methods of the built-in places tree view. if your custom view is used only once in your application, code similar to the above will likely be sufficient; it's enough to create a single placestreeview object, modify it, and attach it to a regular tree. if your view is widely used, however, you may want to take a cue from the built-in tree view and create your own javascript prototype similar to placestreeview and your own xbl tree binding so that much of the work of creating views and viewers and hooking them up to results is abstracted away. the attribute nsinavhistoryresultnode.viewindex is provided explicitly for the use of the view. this value is initialized to -1 when each node is created. you can use this value to keep track of visible nodes. placestreeview uses this a...

NSS API Guidelines
pulled. if you're good with tagging your releases, and then checking out (or exporting!) from the tag for your build, this saves you from messing around with specific files revision numbers. header files we have a preferred naming system for include files. we had been moving towards one, for some time, but for the nss 3.0 project we finally wrote it down. data types function prototypes public nss____t.h nss____.h friend (only if required) nss____tf.h nss____f.h nss-private ____t.h ____.h module-private ____tm.h ____m.h the files on the right include the files to their left; the files in a row include the files directly above them. header files always include what they need; the files are protected against doubl...
...r). note: it's not necessary all eight files exist. further, this is a simple ideal, and often reality is more complex. we would like to keep names to 8.3, even if we no longer support win16. this usually gives us four characters to identify a module of nss. in short: header files for consumption outside nss start with "nss." header files with types have a trailing "t", header files with prototypes don't. "extern" declarations of data also go in the prototypes files. "friend" headers are for things that we really wish weren't used by non-nss code, but which are. those files have a trailing "f," and their use should be deprecated. "module" headers are for things used only within a specific subset of nss; things which would have been "static" if we had combined separate c source files toge...
...doing. note: error stacks are vertical, and never horizontal. if multiple things go wrong simultaneously, and you want to report them all, use another mechanism. errors, though not integers, are done as external constants, instead of preprocessor definitions. this is so any additional error doesn't trigger the entire tree to rebuild. likewise, the external references to errors are made in the prototypes files, with the functions which can return them. error stacks are thread-private. the usual semantic is that public routines clear the stack first, private routines don't. usually, every public routine has a private counterpart, and the implementation of the public routine looks like this: nssimplement rv * nsstype_method ( nsstype *t, nssfoo *arg1, nssbar ...

Rhino serialization
scenes when rhino serializes objects. how rhino serialization works by default, java serialization of an object also serializes objects that are referred to by that object. upon deserialization the initial object and the objects it refers to are all created and the references between the objects are resolved. however, for javascript this creates a problem. ...
...hat are referred to by that object. upon deserialization the initial object and the objects it refers to are all created and the references between the objects are resolved. however, for javascript this creates a problem. javascript objects contain references to prototypes and to parent scopes. default serialization would serialize the object or function we desired but would also serialize object.prototype or even possibly the entire top-level scope and everything it refers to! we want to be able to serialize a javascript object and then deserialize it into a new scope and have all of the references from the deserialized object to prototypes and parent scopes resolved correctly to refer to objects in the new scope. scriptableoutputstream takes a scope as a parameter to its constructor. if in the pr...
...ion. use the addexcludedname method of scriptableoutputstream to add new names. by default, scriptableoutputstream excludes all the names defined using context.initstandardobjects. if you are using rhino serialization in an environment where you always define, say, a constructor foo, you should add the following code before calling writeobject: out.addexcludedname("foo"); out.addexcludedname("foo.prototype"); this code will prevent foo and foo.prototype from being serialized and will cause references to foo or foo.prototype to be resolved to the objects in the new scope upon deserialization. exceptions will be thrown if foo or foo.prototype cannot be found the scopes used in either scriptableoutputstream or scriptableinputstream. rhino serialization in compilation mode serialization works well wit...

Self-hosted builtins in SpiderMonkey
he global object. self-hosted code has access to some functionality that's not available to normal js code. most importantly, it's possible to invoke any function within the scope of any object using the syntax callfunction(fun, receiver, ...args) (or callcontentfunction, see below), which causes fun to be called within the scope of receiver with ...args as its arguments. in contrast to function.prototype.call, this syntax makes it impossible for other code to interfere and gets compiled to bytecode that doesn't have any overhead compared to a normal function invocation. otoh, normal method calls are forbidden in self-hosted code. so instead of receiver.fun(arg1, ..., argn) you have to use callfunction(fun, receiver, arg1, ... argn). this restriction was added because otherwise it's extremely eas...
... functions when assuming that content can't interfere with behavior. e.g., if receiver is an object that content has access to, then callfunction(receiver.fun, receiver) wouldn't be guaranteed to work, because content might have changed the value of receiver.fun, so callcontentfunction(receiver.fun, receiver) has to be used. self-hosted functions by default are not constructors and do not have a prototype property, so that they meet the requirements for standard built-in functions as described in the ecmascript language specification 5.1, clause 15. to make a self-hosted function a constructor, call makeconstructible(functionname) after the function declaration. a prototype property can be added from the self-hosted code itself. all self-hosted functions have direct access to each other and can r...
...a select set of c++-implemented builtins is installed via the intrinsic_functions array in selfhosting.cpp, as described below. using the same mechanism, c++-implemented helper functions are made available to self-hosted code. ...

JIT Optimization Outcomes
because somehow the property was accessed in a way that returned a different type than the expected constant. this is an unlikely failure mode, and should not occur. indictionarymode the object whose property is being accessed is in dictionary mode. objects which are used in ways that suggest they are hashtables are turned into dictionary objects and their types marked as such. noprotofound a prototype object was not found for all the object used by this operation. multiprotopaths objects used in this operation had differing prototypes. nonwritableproperty the property being assigned to is not writable for some types of objects which are used in this operation. protoindexedprops the object being accessed has indexed properties that are exotic (for example, defined as a property on a proto...
...function could not be compiled by the baseline compiler. cantinlinelazy unable to inline function call. the interpreted callee function has a lazy, compiled on-demand script instead of an already compiled script. cantinlinenotconstructor unable to inline function call. rare. the interpreted callee function is invoked with new but cannot be called as a constructor. property accessors, function.prototype, and arrow (=>) functions cannot be called as constructors. cantinlinedisableion unable to inline function call. the interpreted callee function has been explicitly blacklisted against ion compilation. cantinlinetoomanyargs unable to inline function call. the interpreted callee function either has too many parameters or is called with too many arguments. these thresholds are subject to change...
.... the engine knows nothing definite about the type of the callee function object. cantinlineunreachable unable to inline function call. the call site has not been observed to have ever been executed. it lacks observed type information for its arguments, its return value, or both. cantinlinebound unable to inline function call. the interpreted callee is a bound function generated from function.prototype.bind that failed some sub-checks. (expand) cantinlinenativenospecialization unable to inline function call. ion does not have built-in specialization for the native (implemented in c++) callee function. cantinlinenativebadform unable to inline function call. the native callee function was called with an unsupported number of arguments, or calling non-constructing functions with new. cantinli...

JS_NewObjectForConstructor
pi 14 name type description cx jscontext * the context in which to create the new object. requires request. in a js_threadsafe build, the caller must be in a request on this jscontext. clasp const jsclass * the class of the object to create. added in spidermonkey 17 vp jsval * pointer to a constructor. this must be an object that has a prototype property. args js::callargs &amp; call argument to get a constructor as callee. added in spidermonkey 38 description js_newobjectforconstructor creates a new object exactly as the given constructor would if invoked with new. this function does not run the code of the constructor function--it just creates the object. if the constructor argument is not an object jsval, this fun...
... constructor as callee. added in spidermonkey 38 description js_newobjectforconstructor creates a new object exactly as the given constructor would if invoked with new. this function does not run the code of the constructor function--it just creates the object. if the constructor argument is not an object jsval, this function will assert (in debug builds). ...
...th new. this function does not run the code of the constructor function--it just creates the object. if the constructor argument is not an object jsval, this function will assert (in debug builds). if the constructor does not have a prototype property, this function will return null and set an exception on cx. the standard object creation api, js_newobject, takes explicit arguments for the class, prototype, and parent of the new object. with js_newobjectforconstructor, the prototype and parent are determined by the constructor, and class is still determined by the caller. the prototype is the prototype of the constructor if it is an object, otherwise null. the parent is the constructor's parent. see also mxr id search for js_newobjectforconstructor js_newobject object_to_jsval bug 581263 - added ...

Components.utils.Sandbox
org/nullprincipal;1"].createinstance(ci.nsiprincipal); from firefox 37 onwards, you can also specify the null principal by simply passing null as the principal argument. options the constructor accepts an optional parameter. this parameter is an object with the following optional properties: freshzone if true creates a new gc region separate from both the calling context's and the sandbox prototype's region. addons creating sandboxes whose expected lifetime is tied to that of a content window object will want to use samezoneas instead. samezoneas a javascript object in whose garbage collection region the sandbox should be created in. this helps to improve memory usage by allowing sandboxes to be discarded when that zone goes away. content scripts should pass the window they're running ...
...ces in the future). this property is optional, but very useful for tracking memory usage of add-ons and other javascript compartments. a recommended value for this property is an absolute path to the script responsible for creating the sandbox. as of gecko 13 (firefox 13.0 / thunderbird 13.0 / seamonkey 2.10), if you don't specify a sandbox name it will default to the caller's filename. sandboxprototype a prototype object for the sandbox. the sandbox will inherit the contents of this object if it's provided. passing a content window object, setting wantxrays:true (default) and using an extended principal provides a clean, isolated execution environment in which javascript code that needs web apis (such as accessing the window's dom) can be executed without interference from untrusted conten...
... sandbox to be freed immediately. example executing in current tab scope more ways to load scripts into a sandbox can be found on the loading scripts page. this example is to be run from scratchpad with environemnt set to browser. it alerts the dollar sign function. this code was tested on twitter.com and gets access to the jquery $. var sandboxscript = 'alert($)'; var options = { sandboxprototype: content, wantxrays: false // only set this to false if you need direct access to the page's javascript. true provides a safer, isolated context. }; var sandbox = cu.sandbox(content, options); cu.evalinsandbox(sandboxscript, sandbox); cu.nukesandbox(sandbox); ...

Debugger.Memory - Firefox Developer Tools
memory.maxallocationsloglength. censuses a census is a complete traversal of the graph of all reachable memory items belonging to a particular debugger‘s debuggees. it produces a count of those items, broken down by various criteria. ifdbg is a debugger instance, you can call dbg.memory.takecensus to conduct a census of its debuggees’ possessions. accessor properties of the debugger.memory.prototype object ifdbg is a debugger instance, then <i>dbg</i>.memory is a debugger.memory instance, which inherits the following accessor properties from its prototype: trackingallocationsites a boolean value indicating whether this debugger.memory instance is capturing the javascript execution stack when each object is allocated. this accessor property has both a getter and setter: assigning to it...
...es the allocation site tracking. reading the accessor produces true if the debugger is capturing stacks for object allocations, and false otherwise. allocation site tracking is initially disabled in a new debugger. assignment is fallible: if the debugger cannot track allocation sites, it throws an error instance. you can retrieve the allocation site for a given object with the debugger.object.prototype.allocationsite accessor property. allocationsamplingprobability a number between 0 and 1 that indicates the probability with which each new allocation should be entered into the allocations log. 0 is equivalent to “never”, 1 is “always”, and .05 would be “one out of twenty”. the default is 1, or logging every allocation. note that in the presence of multiple debugger instanc...
...ll gc was necessary. otherwise, null is returned. known values include the following: “gc mode” “malloc bytes trigger” “allocation trigger” “requested” gccyclenumber the gc cycle’s “number”. does not correspond to the number of gc cycles that have run, but is guaranteed to be monotonically increasing. function properties of the debugger.memory.prototype object memory use analysis exposes implementation details memory analysis may yield surprising results, because browser implementation details that are transparent to content javascript often have visible effects on memory consumption. web developers need to know their pages’ actual memory consumption on real browsers, so it is correct for the tool to expose these behaviors, as long as it i...

Debugger.Script - Firefox Developer Tools
vior of the property or method differs between the instance referring to a jsscript or to a block of webassembly code, the text will be split into two sections, headed by “if the instance refers to a jsscript” and “if the instance refers to webassembly code”, respectively. if the behavior does not differ, no such emphasized headings will appear. accessor properties of the debugger.script prototype object a debugger.script instance inherits the following accessor properties from its prototype: isgeneratorfunction true if this instance refers to a jsscript for a function defined with a function* expression or statement. false otherwise. isasyncfunction true if this instance refers to a jsscript for an async function, defined with an async function expression or statement. false otherw...
...ebassembly code, throw a typeerror. url if the instance refers to a jsscript, the filename or url from which this script’s code was loaded. for scripts created by eval or the function constructor, this may be a synthesized filename, starting with a valid url and followed by information tracking how the code was introduced into the system; the entire string is not a valid url. for function.prototype’s script, this is null. if this debugger.script’s source property is non-null, then this is equal to source.url. if the instance refers to webassembly code, throw a typeerror. startline if the instance refers to a jsscript, the number of the line at which this script’s code starts, within the file or document named by url. linecount if the instance refers to a jsscript, the number o...
...e referring to the global object in whose scope this script runs. the result refers to the global directly, not via a wrapper or a windowproxy (“outer window”, in firefox). if the instance refers to webassembly code, throw a typeerror. format if the instance refers to a jsscript, "js". if the instance refers to webassembly code, "wasm". function properties of the debugger.script prototype object the functions described below may only be called with a this value referring to a debugger.script instance; they may not be used as methods of other kinds of objects. getalloffsets() if the instance refers to a jsscript, return an arrayl describing the relationship between bytecode instruction offsets and source code positions in this script.l is sparse, and indexed by source line n...

Debugger.Source - Firefox Developer Tools
operty or method differs between the instance referring to javascript source or to a block of webassembly code, the text will be split into two sections, headed by “if the instance refers to javascript source” and “if the instance refers to webassembly code”, respectively. if the behavior does not differ, no such emphasized headings will appear. accessor properties of the debugger.source prototype object a debugger.source instance inherits the following accessor properties from its prototype: text if the instance refers to javascript source, the javascript source code, as a string. the value satisfies the program, functiondeclaration, or functionexpression productions in the ecmascript standard. if the instance refers to webassembly code, the serialized text representation. the fo...
...ains the webassembly bytecode. url if the instance refers to javascript source, the filename or url from which this script’s code was loaded. for scripts created by eval or the function constructor, this may be a synthesized filename, starting with a valid url and followed by information tracking how the code was introduced into the system; the entire string is not a valid url. for function.prototype’s script, this is null. source may be loaded from a url in the following ways: the url may appear as the src attribute of a <script> element in markup text. the url may be passed to the worker web worker constructor, or the web worker importscripts function. the url may be the name of a xpcom javascript module or subscript. (note that code passed to eval, the f...
...ibute, this is the name of that attribute, a string. otherwise, this is undefined. introductiontype if the instance refers to javascript source, a string indicating how this source code was introduced into the system. this accessor returns one of the following values: "eval", for code passed to eval. "function", for code passed to the function constructor. "function.prototype", for function.prototype internally generated code. "worker", for code loaded by calling the web worker constructor—the worker’s main script. "importscripts", for code by calling importscripts in a web worker. "eventhandler", for code assigned to dom elements’ event handler idl attributes as a string. "scriptelement", for code belonging to <script> elemen...

Blob - Web APIs
set of another blob's data, use the slice() method. to obtain a blob object for a file on the user's file system, see the file documentation. the apis accepting blob objects are also listed in the file documentation. constructor blob() returns a newly created blob object which contains a concatenation of all of the data in the array passed into the constructor. instance properties blob.prototype.size read only the size, in bytes, of the data contained in the blob object. blob.prototype.type read only a string indicating the mime type of the data contained in the blob. if the type is unknown, this string is empty. instance methods blob.prototype.arraybuffer() returns a promise that resolves with an arraybuffer containing the entire contents of the blob as binary data. blob.pro...
...he mime type of the data contained in the blob. if the type is unknown, this string is empty. instance methods blob.prototype.arraybuffer() returns a promise that resolves with an arraybuffer containing the entire contents of the blob as binary data. blob.prototype.slice() returns a new blob object containing the data in the specified range of bytes of the blob on which it's called. blob.prototype.stream() returns a readablestream that can be used to read the contents of the blob. blob.prototype.text() returns a promise that resolves with a usvstring containing the entire contents of the blob interpreted as utf-8 text. examples creating a blob the blob() constructor can create blobs from other objects. for example, to construct a blob from a json string: const obj = {hello: 'world'...
...tent of a blob as a typed array: const reader = new filereader(); reader.addeventlistener('loadend', () => { // reader.result contains the contents of blob as a typed array }); reader.readasarraybuffer(blob); another way to read content from a blob is to use a response. the following code reads the content of a blob as text: const text = await (new response(blob)).text(); or by using blob.prototype.text(): const text = await blob.text(); by using other methods of filereader, it is possible to read the contents of a blob as a string or a data url. specifications specification status comment file apithe definition of 'the blob interface' in that specification. working draft initial definition. ...

ChildNode.remove() - Web APIs
living standard initial definition. ...
... living standard initial definition. ...
... living standard initial definition. ...

Element.closest() - Web APIs
> div"); // returns the closest ancestor which is a div and has a parent article, here it is the div-01 var r4 = el.closest(":not(div)"); // returns the closest ancestor which is not a div, here it is the outmost article polyfill for browsers that do not support element.closest(), but carry support for element.matches() (or a prefixed equivalent, meaning ie9+), a polyfill exists: if (!element.prototype.matches) { element.prototype.matches = element.prototype.msmatchesselector || element.prototype.webkitmatchesselector; } if (!element.prototype.closest) { element.prototype.closest = function(s) { var el = this; do { if (element.prototype.matches.call(el, s)) return el; el = el.parentelement || el.parentnode; } while (el !== null && el.nodetype === 1); re...
... return el; el = el.parentelement || el.parentnode; } while (el !== null && el.nodetype === 1); return null; }; } however, if you really do require ie 8 support, then the following polyfill will do the job very slowly, but eventually. however, it will only support css 2.1 selectors in ie 8, and it can cause severe lag spikes in production websites. ...
...telement || el.parentnode; } while (el !== null && el.nodetype === 1); return null; }; } however, if you really do require ie 8 support, then the following polyfill will do the job very slowly, but eventually. however, it will only support css 2.1 selectors in ie 8, and it can cause severe lag spikes in production websites. ...

EventTarget - Web APIs
in mozilla chrome codebase mozilla includes a couple of extensions for use by js-implemented event targets to implement onevent properties. see also webidl bindings. ...
...ludes a couple of extensions for use by js-implemented event targets to implement onevent properties. see also webidl bindings. ...
... handler) eventhandler geteventhandler(domstring type) example simple implementation of eventtarget var eventtarget = function() { this.listeners = {}; }; eventtarget.prototype.listeners = null; eventtarget.prototype.addeventlistener = function(type, callback) { if (!(type in this.listeners)) { this.listeners[type] = []; } this.listeners[type].push(callback); }; eventtarget.prototype.removeeventlistener = function(type, callback) { if (!(type in this.listeners)) { return; } var stack = this.listeners[type]; for (var i = 0, l = stack.length; i < l; i++) { if (stack[i] === callback){ stack.splice(i, 1); return; } } }; eventtarget.prototype.dispatchevent = function(event) { if (!(event.type in this.listeners)) { return true; } var sta...

NonDocumentTypeChildNode.nextElementSibling - Web APIs
e following into the console when it loads: siblings of div-01: div script polyfill for internet explorer 8 this property is unsupported prior to ie9, so the following snippet can be used to add support to ie8: // source: https://github.com/alhadis/snippets/blob/master/js/polyfills/ie8-child-elements.js if(!("nextelementsibling" in document.documentelement)){ object.defineproperty(element.prototype, "nextelementsibling", { get: function(){ var e = this.nextsibling; while(e && 1 !== e.nodetype) e = e.nextsibling; return e; } }); } polyfill for internet explorer 9+ and safari // source: https://github.com/jserz/js_piece/blob/master/dom/nondocumenttypechildnode/nextelementsibling/nextelementsibling.md (function (arr) { ...
... living standard split the elementtraversal interface in childnode, parentnode, and nondocumenttypechildnode. this method is now defined on the former. the element and characterdata interfaces implemented the new inter...
... living standard split the elementtraversal interface in childnode, parentnode, and nondocumenttypechildnode. this method is now defined on the former. the element and characterdata interfaces implemented the new interface. element tr...

NonDocumentTypeChildNode.previousElementSibling - Web APIs
s: siblings of div-03 1. li 2. li 3. div 4. ...
... living standard splitted the elementtraversal interface in childnode, parentnode, and nondocumenttypechildnode. this method is now defined on the former. the element and characterdata interfaces im...
... living standard splitted the elementtraversal interface in childnode, parentnode, and nondocumenttypechildnode. this method is now defined on the former. the element and characterdata interfaces implemented the new interfa...

ParentNode.childElementCount - Web APIs
representing a document, documentfragment, or element. example var foo = document.getelementbyid('foo'); if (foo.childelementcount > 0) { // do something } polyfill for ie8 & ie9 & safari this property is completely unsupported prior to ie9. in ie9 and safari, it is unsupported in the document and documentfragment objects. ...
...entfragment, or element. example var foo = document.getelementbyid('foo'); if (foo.childelementcount > 0) { // do something } polyfill for ie8 & ie9 & safari this property is completely unsupported prior to ie9. in ie9 and safari, it is unsupported in the document and documentfragment objects. ...
... if (foo.childelementcount > 0) { // do something } polyfill for ie8 & ie9 & safari this property is completely unsupported prior to ie9. in ie9 and safari, it is unsupported in the document and documentfragment objects. ...

XMLHttpRequest.sendAsBinary() - Web APIs
can create the binary string using the filereader method readasbinarystring(). the string is converted to binary for transfer by removing the high-order byte of each character. return value undefined. polyfill since sendasbinary() is an experimental feature, here is a polyfill for browsers that don't support the sendasbinary() method but support typed arrays. ...
...igh-order byte of each character. return value undefined. polyfill since sendasbinary() is an experimental feature, here is a polyfill for browsers that don't support the sendasbinary() method but support typed arrays. ...
...value undefined. polyfill since sendasbinary() is an experimental feature, here is a polyfill for browsers that don't support the sendasbinary() method but support typed arrays. ...

About JavaScript - JavaScript
what is javascript? javascript® (often shortened to js) is a lightweight, interpreted, object-oriented language with first-class functions, and is best known as the scripting language for web pages, but it's used in many non-browser environments as well. it is a prototype-based, multi-paradigm scripting language that is dynamic, and supports object-oriented, imperative, and functional programming styles. javascript runs on the client side of the web, which can be used to design / program how the web pages behave on the occurrence of an event. javascript is an easy to learn and also powerful scripting language, widely used for controlling web page behavior. contrary to popular misconception, javascript is not "interpreted java". in a nutshell, javascript is a dynamic scripting language supporti...
...javascript runs on the client side of the web, which can be used to design / program how the web pages behave on the occurrence of an event. javascript is an easy to learn and also powerful scripting language, widely used for controlling web page behavior. contrary to popular misconception, javascript is not "interpreted java". in a nutshell, javascript is a dynamic scripting language supporting prototype based object construction. the basic syntax is intentionally similar to both java and c++ to reduce the number of new concepts required to learn the language. language constructs, such as if statements, for and while loops, and switch and try ... catch blocks function the same as in these languages (or nearly so). javascript can function as both a procedural and an object oriented language. obje...
...se languages (or nearly so). javascript can function as both a procedural and an object oriented language. objects are created programmatically in javascript, by attaching methods and properties to otherwise empty objects at run time, as opposed to the syntactic class definitions common in compiled languages like c++ and java. once an object has been constructed it can be used as a blueprint (or prototype) for creating similar objects. javascript's dynamic capabilities include runtime object construction, variable parameter lists, function variables, dynamic script creation (via eval), object introspection (via for ... in), and source code recovery (javascript programs can decompile function bodies back into their source text). for a more in depth discussion of javascript programming follow the ...

Closures - JavaScript
p(text.help); } }); } setuphelp(); performance considerations it is unwise to unnecessarily create functions within other functions if closures are not needed for a particular task, as it will negatively affect script performance both in terms of processing speed and memory consumption. for instance, when creating a new object/class, methods should normally be associated to the object's prototype rather than defined into the object constructor. the reason is that whenever the constructor is called, the methods would get reassigned (that is, for every object creation). consider the following case: function myobject(name, message) { this.name = name.tostring(); this.message = message.tostring(); this.getname = function() { return this.name; }; this.getmessage = function() {...
... function() { return this.name; }; this.getmessage = function() { return this.message; }; } because the previous code does not take advantage of the benefits of using closures in this particular instance, we could instead rewrite it to avoid using closure as follows: function myobject(name, message) { this.name = name.tostring(); this.message = message.tostring(); } myobject.prototype = { getname: function() { return this.name; }, getmessage: function() { return this.message; } }; however, redefining the prototype is not recommended. the following example instead appends to the existing prototype: function myobject(name, message) { this.name = name.tostring(); this.message = message.tostring(); } myobject.prototype.getname = function() { return this.na...
...function() { return this.name; }, getmessage: function() { return this.message; } }; however, redefining the prototype is not recommended. the following example instead appends to the existing prototype: function myobject(name, message) { this.name = name.tostring(); this.message = message.tostring(); } myobject.prototype.getname = function() { return this.name; }; myobject.prototype.getmessage = function() { return this.message; }; in the two previous examples, the inherited prototype can be shared by all objects and the method definitions need not occur at every object creation. see details of the object model for more. ...

Indexed collections - JavaScript
ot share all of their methods. the arguments object provides a length attribute but does not implement the foreach() method, for example. array methods cannot be called directly on array-like objects. ...
...vides a length attribute but does not implement the foreach() method, for example. array methods cannot be called directly on array-like objects. function printarguments() { arguments.foreach(function(item) { // typeerror: arguments.foreach is not a function console.log(item); }); } but you can call them indirectly using function.prototype.call(). ...
...methods cannot be called directly on array-like objects. function printarguments() { arguments.foreach(function(item) { // typeerror: arguments.foreach is not a function console.log(item); }); } but you can call them indirectly using function.prototype.call(). function printarguments() { array.prototype.foreach.call(arguments, function(item) { console.log(item); }); } array prototype methods can be used on strings as well, since they provide sequential access to their characters in a similar way to arrays: array.prototype.foreach.call('a string', function(chr) { console.log(chr) }) typed arrays javascript typed arrays are array-like objects and provide a mechanism for accessing raw binary data. as you already know, array objects grow and shrink dynamically and can have ...

JavaScript error reference - JavaScript
uality (==) mistyped as assignment (=)?syntaxerror: unterminated string literaltypeerror: "x" has no propertiestypeerror: "x" is (not) "y"typeerror: "x" is not a constructortypeerror: "x" is not a functiontypeerror: "x" is not a non-null objecttypeerror: "x" is read-onlytypeerror: 'x' is not iterabletypeerror: more arguments neededtypeerror: reduce of empty array with no initial valuetypeerror: x.prototype.y called on incompatible typetypeerror: can't access dead objecttypeerror: can't access property "x" of "y"typeerror: can't assign to property "x" on "y": not an objecttypeerror: can't define property "x": "obj" is not extensibletypeerror: can't delete non-configurable array elementtypeerror: can't redefine non-configurable property "x"typeerror: cannot use "in" operator to search for "x" in "y"t...
... "x" of "y"typeerror: can't assign to property "x" on "y": not an objecttypeerror: can't define property "x": "obj" is not extensibletypeerror: can't delete non-configurable array elementtypeerror: can't redefine non-configurable property "x"typeerror: cannot use "in" operator to search for "x" in "y"typeerror: cyclic object valuetypeerror: invalid "instanceof" operand "x"typeerror: invalid array.prototype.sort argumenttypeerror: invalid argumentstypeerror: invalid assignment to const "x"typeerror: property "x" is non-configurable and can't be deletedtypeerror: setting getter-only property "x"typeerror: variable "x" redeclares argumenturierror: malformed uri sequencewarning: 08/09 is not a legal ecma-262 octal constantwarning: -file- is being assigned a //# sourcemappingurl, but already has onewarn...
...menttypeerror: invalid argumentstypeerror: invalid assignment to const "x"typeerror: property "x" is non-configurable and can't be deletedtypeerror: setting getter-only property "x"typeerror: variable "x" redeclares argumenturierror: malformed uri sequencewarning: 08/09 is not a legal ecma-262 octal constantwarning: -file- is being assigned a //# sourcemappingurl, but already has onewarning: date.prototype.tolocaleformat is deprecatedwarning: javascript 1.6's for-each-in loops are deprecatedwarning: string.x is deprecated; use string.prototype.x insteadwarning: expression closures are deprecatedwarning: unreachable code after return statement ...

The arguments object - JavaScript
em as follows: arguments[0] // first argument arguments[1] // second argument arguments[2] // third argument each argument can also be set or reassigned: arguments[1] = 'new value'; the arguments object is not an array. it is similar, but lacks all array properties except length. for example, it does not have the pop() method. ...
...iterator] returns a new array iterator object that contains the values for each index in arguments. examples defining a function that concatenates several strings this example defines a function that concatenates several strings. the function's only formal argument is a string containing the characters that separate the items to concatenate. function myconcat(separator) { let args = array.prototype.slice.call(arguments, 1); return args.join(separator); } you can pass as many arguments as you like to this function. it returns a string list using each argument in the list: // returns "red, orange, blue" myconcat(', ', 'red', 'orange', 'blue'); // returns "elephant; giraffe; lion; cheetah" myconcat('; ', 'elephant', 'giraffe', 'lion', 'cheetah'); // returns "sage. basil. oregano. pepper.
... defining a function that creates html lists this example defines a function that creates a string containing html for a list. the only formal argument for the function is a string that is "u" if the list is to be unordered (bulleted), or "o" if the list is to be ordered (numbered). the function is defined as follows: function list(type) { var html = '<' + type + 'l><li>'; var args = array.prototype.slice.call(arguments, 1); html += args.join('</li><li>'); html += '</li></' + type + 'l>'; // end list return html; } you can pass any number of arguments to this function, and it adds each argument as a list item to a list of the type indicated. for example: let listhtml = list('u', 'one', 'two', 'three'); /* listhtml is: "<ul><li>one</li><li>two</li><li>three</li></ul>" */ rest, defau...

Array.isArray() - JavaScript
ed; otherwise, false is. see the article “determining with absolute accuracy whether or not a javascript object is an array” for more details. given a typedarray instance, false is always returned. polyfill running the following code before any other code will create array.isarray() if it's not natively available. ...
...it's not natively available. ...
...{ array.isarray = function(arg) { return object.prototype.tostring.call(arg) === '[object array]'; }; } examples using array.isarray // all following calls return true array.isarray([]); array.isarray([1]); array.isarray(new array()); array.isarray(new array('a', 'b', 'c', 'd')); array.isarray(new array(3)); // little known fact: array.prototype itself is an array: array.isarray(array.prototype); // all following calls return false array.isarray(); array.isarray({}); array.isarray(null); array.isarray(undefined); array.isarray(17); array.isarray('array'); array.isarray(true); array.isarray(false); array.isarray(new uint8array(32)); array.isarray({ __proto__: array.prototype }); instanceof vs isarray when checking for array instance, array.isarray is preferred over instanceof because...

BigInt - JavaScript
12n 0n && 12n // ↪ 0n boolean(0n) // ↪ false boolean(12n) // ↪ true !12n // ↪ false !0n // ↪ true constructor bigint() creates a new bigint value. static methods bigint.asintn() wraps a bigint value to a signed integer between -2width-1 and 2width-1 - 1. bigint.asuintn() wraps a bigint value to an unsigned integer between 0 and 2width - 1. instance methods bigint.prototype.tolocalestring() returns a string with a language-sensitive representation of this number. overrides the object.prototype.tolocalestring() method. bigint.prototype.tostring() returns a string representing the specified object in the specified radix (base). overrides the object.prototype.tostring() method. bigint.prototype.valueof() returns the primitive value of the specified object. overrid...
... usage recommendations coercion because coercing between number and bigint can lead to loss of precision, it is recommended to only use bigint when values greater than 253 are reasonably expected and not to coerce between the two types. ...
...easonably expected and not to coerce between the two types. cryptography the operations supported on bigints are not constant time. bigint is therefore unsuitable for use in cryptography. use within json using json.stringify() with any bigint value will raise a typeerror as bigint values aren't serialized in json by default. ...

Intl.Collator - JavaScript
ve examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request. constructor intl.collator() creates a new collator object. static methods intl.collator.supportedlocalesof() returns an array containing those of the provided locales that are supported without having to fall back to the runtime's default locale. instance methods intl.collator.prototype.compare getter function that compares two strings according to the sort order of this intl.collator object. intl.collator.prototype.resolvedoptions() returns a new object with properties reflecting the locale and collation options computed during initialization of the object. examples using collator the following example demonstrates the different potential results for a string occurring b...
...('c', 'a')); // → a positive value console.log(new intl.collator().compare('a', 'a')); // → 0 note that the results shown in the code above can vary between browsers and browser versions. this is because the values are implementation-specific. that is, the specification requires only that the before and after values are negative and positive. using locales the results provided by collator.prototype.compare() vary between languages. in order to get the sort order of the language used in the user interface of your application, make sure to specify that language (and possibly some fallback languages) using the locales argument: // in german, ä sorts with a console.log(new intl.collator('de').compare('ä', 'z')); // → a negative value // in swedish, ä sorts after z console.log(new intl.co...
... of your application, make sure to specify that language (and possibly some fallback languages) using the locales argument: // in german, ä sorts with a console.log(new intl.collator('de').compare('ä', 'z')); // → a negative value // in swedish, ä sorts after z console.log(new intl.collator('sv').compare('ä', 'z')); // → a positive value using options the results provided by collator.prototype.compare() can be customized using the options argument: // in german, ä has a as the base letter console.log(new intl.collator('de', { sensitivity: 'base' }).compare('ä', 'a')); // → 0 // in swedish, ä and a are separate base letters console.log(new intl.collator('sv', { sensitivity: 'base' }).compare('ä', 'a')); // → a positive value specifications specification ec...

Number - JavaScript
in javascript (-(253 - 1)). number.min_value the smallest positive representable number—that is, the positive number closest to zero (without actually being zero). number.nan special "not a number" value. number.negative_infinity special value representing negative infinity. returned on overflow. number.positive_infinity special value representing infinity. returned on overflow. number.prototype allows the addition of properties to the number object. static methods number.isnan() determine whether the passed value is nan. number.isfinite() determine whether the passed value is a finite number. number.isinteger() determine whether the passed value is an integer. number.issafeinteger() determine whether the passed value is a safe integer (number between -(253 - 1) and 253 - 1)...
...ite number. number.isinteger() determine whether the passed value is an integer. number.issafeinteger() determine whether the passed value is a safe integer (number between -(253 - 1) and 253 - 1). number.parsefloat(string) this is the same as the global parsefloat() function. number.parseint(string, [radix]) this is the same as the global parseint() function. instance methods number.prototype.toexponential(fractiondigits) returns a string representing the number in exponential notation. number.prototype.tofixed(digits) returns a string representing the number in fixed-point notation. number.prototype.tolocalestring([locales [, options]]) returns a string with a language sensitive representation of this number. overrides the object.prototype.tolocalestring() method. number.protot...
... string representing the number in fixed-point notation. number.prototype.tolocalestring([locales [, options]]) returns a string with a language sensitive representation of this number. overrides the object.prototype.tolocalestring() method. number.prototype.toprecision(precision) returns a string representing the number to a specified precision in fixed-point or exponential notation. number.prototype.tostring([radix]) returns a string representing the specified object in the specified radix ("base"). overrides the object.prototype.tostring() method. number.prototype.valueof() returns the primitive value of the specified object. overrides the object.prototype.valueof() method. examples using the number object to assign values to numeric variables the following example uses the number ob...

Object.assign() - JavaScript
key. later sources' properties overwrite earlier ones. the object.assign() method only copies enumerable and own properties from a source object to a target object. it uses [[get]] on the source and [[set]] on the target, so it will invoke getters and setters. therefore it assigns properties, versus copying or defining new properties. this may make it unsuitable for merging new properties into a prototype if the merge sources contain getters. for copying property definitions (including their enumerability) into prototypes, use object.getownpropertydescriptor() and object.defineproperty() instead. both string and symbol properties are copied. in case of an error, for example if a property is non-writable, a typeerror is raised, and the target object is changed if any properties are added before ...
...ow new typeerror('cannot convert undefined or null to object'); } var to = object(target); for (var index = 1; index < arguments.length; index++) { var nextsource = arguments[index]; if (nextsource !== null && nextsource !== undefined) { for (var nextkey in nextsource) { // avoid bugs when hasownproperty is shadowed if (object.prototype.hasownproperty.call(nextsource, nextkey)) { to[nextkey] = nextsource[nextkey]; } } } } return to; }, writable: true, configurable: true }); } examples cloning an object const obj = { a: 1 }; const copy = object.assign({}, obj); console.log(copy); // { a: 1 } warning for deep clone for deep cloning, we need to use alterna...
... c: 3 } the properties are overwritten by other objects that have the same properties later in the parameters order. copying symbol-typed properties const o1 = { a: 1 }; const o2 = { [symbol('foo')]: 2 }; const obj = object.assign({}, o1, o2); console.log(obj); // { a : 1, [symbol("foo")]: 2 } (cf. bug 1207182 on firefox) object.getownpropertysymbols(obj); // [symbol(foo)] properties on the prototype chain and non-enumerable properties cannot be copied const obj = object.create({ foo: 1 }, { // foo is on obj's prototype chain. bar: { value: 2 // bar is a non-enumerable property. }, baz: { value: 3, enumerable: true // baz is an own enumerable property. } }); const copy = object.assign({}, obj); console.log(copy); // { baz: 3 } primitives will be wrapped to objects c...

Object.getOwnPropertyDescriptors() - JavaScript
le true if and only if this property shows up during enumeration of the properties on the corresponding object. ...
...as the object.assign() method will only copy enumerable and own properties from a source object to a target object, you are able to use this method and object.create() for a shallow copy between two unknown objects: object.create( object.getprototypeof(obj), object.getownpropertydescriptors(obj) ); creating a subclass a typical way of creating a subclass is to define the subclass, set its prototype to an instance of the superclass, and then define properties on that instance. this can get awkward especially for getters and setters. ...
...etween two unknown objects: object.create( object.getprototypeof(obj), object.getownpropertydescriptors(obj) ); creating a subclass a typical way of creating a subclass is to define the subclass, set its prototype to an instance of the superclass, and then define properties on that instance. this can get awkward especially for getters and setters. instead, you can use this code to set the prototype: function superclass() {} superclass.prototype = { // define your methods and properties here }; function subclass() {} subclass.prototype = object.create( superclass.prototype, { // define your methods and properties here } ); specifications specification ecmascript (ecma-262)the definition of 'object.getownpropertydescriptors' in that specification. ...

RangeError - JavaScript
the rangeerror object indicates an error when a value is not in the set or range of allowed values. description a rangeerror is thrown when trying to pass a value as an argument to a function that does not allow a range that includes the value. this can be encountered when: passing a value that is not one of the allowed string values to string.prototype.normalize(), or when attempting to create an array of an illegal length with the array constructor, or when passing bad values to the numeric methods number.prototype.toexponential(), number.prototype.tofixed() or number.prototype.toprecision(). constructor rangeerror() creates a new rangeerror object. instance properties rangeerror.prototype.message error message. although ecma-262 specifies that rangeerror should provide its o...
...r when passing bad values to the numeric methods number.prototype.toexponential(), number.prototype.tofixed() or number.prototype.toprecision(). constructor rangeerror() creates a new rangeerror object. instance properties rangeerror.prototype.message error message. although ecma-262 specifies that rangeerror should provide its own message property, in spidermonkey, it inherits error.prototype.message. rangeerror.prototype.name error name. inherited from error. rangeerror.prototype.filename path to file that raised this error. inherited from error. rangeerror.prototype.linenumber line number in file that raised this error. inherited from error. rangeerror.prototype.columnnumber column number in line that raised this error. ...
...inherited from error. ...

Reflect - JavaScript
es the following static functions which have the same names as the proxy handler methods. some of these methods are also the same as corresponding methods on object, although they do have some subtle differences between them. static methods reflect.apply(target, thisargument, argumentslist) calls a target function with arguments as specified by the argumentslist parameter. see also function.prototype.apply(). reflect.construct(target, argumentslist[, newtarget]) the new operator as a function. equivalent to calling new target(...argumentslist). also provides the option to specify a different prototype. reflect.defineproperty(target, propertykey, attributes) similar to object.defineproperty(). returns a boolean that is true if the property was successfully defined. reflect.deleteproperty(...
...arget[propertykey]. reflect.get(target, propertykey[, receiver]) returns the value of the property. works like getting a property from an object (target[propertykey]) as a function. reflect.getownpropertydescriptor(target, propertykey) similar to object.getownpropertydescriptor(). returns a property descriptor of the given property if it exists on the object, undefined otherwise. reflect.getprototypeof(target) same as object.getprototypeof(). reflect.has(target, propertykey) returns a boolean indicating whether the target has the property. either as own or inherited. works like the in operator as a function. reflect.isextensible(target) same as object.isextensible(). returns a boolean that is true if the target is extensible. reflect.ownkeys(target) returns an array of the target objec...
...wnkeys(target) returns an array of the target object's own (not inherited) property keys. reflect.preventextensions(target) similar to object.preventextensions(). returns a boolean that is true if the update was successful. reflect.set(target, propertykey, value[, receiver]) a function that assigns values to properties. returns a boolean that is true if the update was successful. reflect.setprototypeof(target, prototype) a function that sets the prototype of an object. returns a boolean that is true if the update was successful. examples detecting whether an object contains certain properties const duck = { name: 'maurice', color: 'white', greeting: function() { console.log(`quaaaack! my name is ${this.name}`); } } reflect.has(duck, 'color'); // true reflect.has(duck, 'hairc...