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Closures - JavaScript
in javascript,
closures are created every time a function is created, at function creation time.
... the reason is that functions in javascript form
closures.
... add5 and add10 are both
closures.
...And 18 more matches
Warning: expression closures are deprecated - JavaScript
the javascript warning "expression
closures are deprecated" occurs when the non-standard expression closure syntax (shorthand function syntax) is used.
... message warning: expression
closures are deprecated error type warning.
... examples deprecated syntax expression
closures omit curly braces or return statements from function declarations or from method definitions in objects.
...And 2 more matches
Functions
(nameexpressions are basic expressions like string and x that would eat up a huge amount of run time if the engine weren't smart enough to avoid symbol table lookups.) general
closures are the base case.
...general
closures force the interpreter to verify the whole scope chain.
...null
closures.
...And 6 more matches
Avoiding leaks in JavaScript XPCOM components
however, it's easy to inadvertently create this same type of leak when using
closures.
... to understand
closures a little better before examining how they can cause leaks, consider the following example, in which there are two pairs of function objects, and each pair has an instance of the private_data variable: // this function returns an array containing two functions.
...ubles first private_data to 2 fns1[1]() + ", " + // doubles first private_data to 4 fns2[1]() + ", " + // doubles second private_data to 0 fns1[0]() + ", " + // increments first private_data to 5 fns2[0]() + ", " + // increments second private_data to 1 fns1[1]() + "."; // doubles first private_data to 10 } this shows that
closures are quite powerful.
...And 2 more matches
Functions - JavaScript
the stack-like behavior can be seen in the following example: function foo(i) { if (i < 0) return; console.log('begin: ' + i); foo(i - 1); console.log('end: ' + i); } foo(3); // output: // begin: 3 // begin: 2 // begin: 1 // begin: 0 // end: 0 // end: 1 // end: 2 // end: 3 nested functions and
closures you may nest a function within another function.
... both functions b and c form
closures here.
... thus, the
closures can contain multiple scopes; they recursively contain the scope of the functions containing it.
...And 2 more matches
Private Properties - Archive of obsolete content
this article discusses two common techniques: one using prefixes, the other
closures.
... using
closures another common technique, is to define private properties as variables and their getter and setter functions as a closure over these variables: 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; }; } n...
...however, the use of
closures makes private properties too restrictive: since there is no way to access variables in one closure from within another closure, there is no way for objects of the same class to access each other's private properties.
... using weakmaps the techniques above are either not restrictive enough (prefixes) or too restrictive (
closures), however the recent introduction of weakmaps provides a solution.
A re-introduction to JavaScript (JS tutorial) - JavaScript
closures this leads us to one of the most powerful abstractions that javascript has to offer — but also the most potentially confusing.
...
closures let you save state — as such, they can often be used in place of objects.
... you can find several excellent introductions to
closures.
JavaScript Daemons Management - Archive of obsolete content
the architecture of the daemon constructor explicitly avoids the use of
closures.
... advantages of this approch: abstraction passage of this object to javascript timers (both setinterval and settimeout) optimisation (avoiding
closures) modularity the code the code of this framework is split into three files: daemon.js (the core) daemon-safe.js (an extension of the core which adds a replacement of setinterval with a recursive invocation of settimeout) daemon-methods.js (a wide and highly scalable collection of methods) the only independent module is daemon.js: both the daemon-safe.js module and the daemon-methods.js module require daemon.js to work.
Index - Archive of obsolete content
this article discusses two common techniques: one using prefixes, the other
closures.
... 2010 expression
closures function, javascript, language feature, non-standard, obsolete, operator, reference expression
closures are a shorthand function syntax for writing simple functions.
How to build custom form controls - Learn web development
nitialized selectlist.foreach(function (select) { // as well as all its `option` elements var optionlist = select.queryselectorall('.option'); // each time a user hovers their mouse over an option, we highlight the given option optionlist.foreach(function (option) { option.addeventlistener('mouseover', function () { // note: the `select` and `option` variable are
closures // available in the scope of our function call.
... // we toggle the visibility of the list of options toggleoptlist(select); }); // in case the control gains focus // the control gains the focus each time the user clicks on it or each time // they use the tabulation key to access the control select.addeventlistener('focus', function (event) { // note: the `select` and `selectlist` variable are
closures // available in the scope of our function call.
Functions — reusable blocks of code - Learn web development
the lions, zebras, tigers, and penguins are kept in their own en
closures, and only have access to the things inside their en
closures — in the same manner as the function scopes.
... if they were able to get into other en
closures, problems would occur.
JSFunction
different
closures (function objects) generated from the same source code may share the same jsfunction.
... as a result, some apis (such as js_callfunction) that operate on jsfunctions do not work properly with
closures.
nsIFeedEntry
en
closures nsiarray an array of all the en
closures included in the entry.
... mediacontent nsiarray an array of all the en
closures or other media that might be displayed inline in the entry.
let - JavaScript
for example: var x = 'global'; let y = 'global'; console.log(this.x); // "global" console.log(this.y); // undefined emulating private members in dealing with constructors it is possible to use the let bindings to share one or more private members without using
closures: var thing; { let privatescope = new weakmap(); let counter = 0; thing = function() { this.someproperty = 'foo'; privatescope.set(this, { hidden: ++counter, }); }; thing.prototype.showpublic = function() { return this.someproperty; }; thing.prototype.showprivate = function() { return privatescope.get(this).hidden; }; } console.log(typeof privatesco...
...pe); // "undefined" var thing = new thing(); console.log(thing); // thing {someproperty: "foo"} thing.showpublic(); // "foo" thing.showprivate(); // 1 the same privacy pattern with
closures over local variables can be created with var, but those need a function scope (typically an iife in the module pattern) instead of just a block scope like in the example above.
Guides - Archive of obsolete content
private properties learn how private properties can be implemented in javascript using prefixes,
closures, and weakmaps, and how the sdk supports private properties by using namespaces (which are a generalization of weakmaps).
Use Case - Archive of obsolete content
use cases between rss aggregators and rss feeds polling rss feeds figuring out which version of rss 0.91 you have how to handle en
closures http mime type handling use cases between users and rss feeds subscribing to an rss feed ...
E4X for templating - Archive of obsolete content
while it may be obvious after a study of the basics of e4x that it can be used for this purpose, if one adds a few common purpose functions (especially along with the convenience of javascript 1.8 expression
closures), the templates can function more dynamically, offering the power and readability of templating languages such as smarty for php (though admittedly without the currently wider cross-browser support of xslt or the strictly-xml approach of phptal or seethrough templating).
Archived JavaScript Reference - Archive of obsolete content
see also the newer version of date.prototype.tolocaledatestring().ecmascript 2016 to es.next support in mozillaexpression
closuresexpression
closures are a shorthand function syntax for writing simple functions.for each...inthe for each...in statement iterates a specified variable over all values of object's properties.
asm.js - Game development
it does not allow objects, strings,
closures, and basically anything that requires heap allocation.
Bytecode Descriptions
the optimization that puts bindings in stack slots has to prove that the bindings won't need to be captured by
closures or accessed using jsop::{get,bind,set,del}name instructions.
JS_GetFunctionFlags
jsfun_heavyweight the function uses language features such as
closures, with, or eval that require extra work on the part of the interpreter.
JS_GetFunctionObject
however, for other functions, and particularly for javascript
closures, many jsobjects may share the same jsfunction.
Parser API
note: expression
closures are spidermonkey-specific.
SpiderMonkey 1.8
new javascript language features javascript 1.8 adds array.reduce() and reduceright(), expression
closures, and generator expressions.
nsIFeed
enclosurecount long indicates the number of en
closures associated with a feed.
Using Objective-C from js-ctypes
probably used in more * complex block scenarios involving actual closure variables needing storage * (in `nodobjc`, javascript
closures are leveraged instead).
Memory Management
closures you also need to be sure to retain references to any javascript code that native code may call back into.
JavaScript Guide - JavaScript
ar and types basic syntax & comments declarations variable scope variable hoisting data structures and types literals control flow and error handling if...else switch try/catch/throw error objects loops and iteration for while do...while break/continue for..in for..of functions defining functions calling functions function scope
closures arguments & parameters arrow functions expressions and operators assignment & comparisons arithmetic operators bitwise & logical operators conditional (ternary) operator numbers and dates number literals number object math object date object text formatting string literals string object template literals internationalization regular expressions ...
SyntaxError: missing } after function body - JavaScript
examples forgotten closing curly bracket oftentimes, there is a missing curly bracket in your function code: var charge = function() { if (sunny) { usesolarcells(); } else { promptbikeride(); }; correct would be: var charge = function() { if (sunny) { usesolarcells(); } else { promptbikeride(); } }; it can be more obscure when using iife,
closures, or other constructs that use a lot of different parenthesis and curly brackets, for example.
JavaScript error reference - JavaScript
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 ...
AsyncFunction - JavaScript
note: async functions created with the asyncfunction constructor do not create
closures to their creation contexts; they are always created in the global scope.
Function.prototype.apply() - JavaScript
for alternative methods, please consider one of the following approaches: using object.__proto__: function.prototype.construct = function (aargs) { let onew = {}; onew.__proto__ = this.prototype; this.apply(onew, aargs); return onew; }; using
closures: function.prototype.construct = function(aargs) { let fconstructor = this, fnewconstr = function() { fconstructor.apply(this, aargs); }; fnewconstr.prototype = fconstructor.prototype; return new fnewconstr(); }; using the function constructor: function.prototype.construct = function (aargs) { let fnewconstr = new function(""); fnewconstr.prototype = this.prototype; let onew =...
Function - JavaScript
examples difference between function constructor and function declaration functions created with the function constructor do not create
closures to their creation contexts; they always are created in the global scope.
GeneratorFunction - JavaScript
note: generator function created with the generatorfunction constructor do not create
closures to their creation contexts; they are always created in the global scope.
WeakRef - JavaScript
the javascript engine may hold references to things which look like they are unreachable (e.g., in
closures, or inline caches).
eval() - JavaScript
} , false);
closures are also helpful as a way to create parameterized functions without concatenating strings.
return - JavaScript
function counter() { for (var count = 1; ; count++) { // infinite loop console.log(count + 'a'); // until 5 if (count === 5) { return; } console.log(count + 'b'); // until 4 } console.log(count + 'c'); // never appears } counter(); // output: // 1a // 1b // 2a // 2b // 3a // 3b // 4a // 4b // 5a returning a function see also the article about
closures.
var - JavaScript
the scope of a variable declared with var is its current execution context and
closures thereof, which is either the enclosing function and functions declared within it, or, for variables declared outside any function, global.
JavaScript
closures a closure is the combination of a function and the lexical environment within which that function was declared.