Every JavaScript function is actually a Function
object. This can be seen with the code (function(){}).constructor === Function
, which returns true.
Constructor
Function()
- Creates a new
Function
object. Calling the constructor directly can create functions dynamically but suffers from security and similar (but far less significant) performance issues toeval
. However, unlike eval, theFunction
constructor creates functions that execute in the global scope only.
Instance properties
Function.arguments
- An array corresponding to the arguments passed to a function.
This is deprecated as a property ofFunction
. Use thearguments
object (available within the function) instead. Function.caller
- Specifies the function that invoked the currently executing function.
This property is deprecated, and is only functional for some non-strict functions. Function.displayName
- The display name of the function.
Function.length
- Specifies the number of arguments expected by the function.
Function.name
- The name of the function.
Instance methods
Function.prototype.apply(thisArg [, argsArray])
- Calls a function and sets its
this
to the providedthisArg
. Arguments can be passed as anArray
object. Function.prototype.bind(thisArg[, arg1[, arg2[, ...argN]]])
- Creates a new function which, when called, has its
this
set to the providedthisArg
. Optionally, a given sequence of arguments will be prepended to arguments provided the newly-bound function is called. Function.prototype.call(thisArg[, arg1, arg2, ...argN])
- Calls a function and sets its
this
to the provided value. Arguments can be passed as they are. Function.prototype.toString()
- Returns a string representing the source code of the function.
Overrides theObject.prototype.toString
method.
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. When running them, they will only be able to access their own local variables and global ones, not the ones from the scope in which the Function
constructor was created. This is different from using eval
with code for a function expression.
var x = 10; function createFunction1() { var x = 20; return new Function('return x;'); // this |x| refers global |x| } function createFunction2() { var x = 20; function f() { return x; // this |x| refers local |x| above } return f; } var f1 = createFunction1(); console.log(f1()); // 10 var f2 = createFunction2(); console.log(f2()); // 20
While this code works in web browsers, f1()
will produce a ReferenceError
in Node.js, as x
will not be found. This is because the top-level scope in Node is not the global scope, and x
will be local to the module.
Specifications
Specification |
---|
ECMAScript (ECMA-262) The definition of 'Function' in that specification. |
Browser compatibility
The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request.
Desktop | Mobile | Server | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Function | Chrome Full support 1 | Edge Full support 12 | Firefox Full support 1 | IE Full support 4 | Opera Full support 3 | Safari Full support 1 | WebView Android Full support 1 | Chrome Android Full support 18 | Firefox Android Full support 4 | Opera Android Full support 10.1 | Safari iOS Full support 1 | Samsung Internet Android Full support 1.0 | nodejs Full support Yes |
Function() constructor | Chrome Full support 1 | Edge Full support 12 | Firefox Full support 1 | IE Full support 4 | Opera Full support 3 | Safari Full support 1 | WebView Android Full support 1 | Chrome Android Full support 18 | Firefox Android Full support 4 | Opera Android Full support 10.1 | Safari iOS Full support 1 | Samsung Internet Android Full support 1.0 | nodejs Full support Yes |
apply | Chrome Full support 1 | Edge Full support 12 | Firefox Full support 1 | IE Full support 5.5 | Opera Full support 4 | Safari Full support 1 | WebView Android Full support 1 | Chrome Android Full support 18 | Firefox Android Full support 4 | Opera Android Full support 10.1 | Safari iOS Full support 1 | Samsung Internet Android Full support 1.0 | nodejs Full support Yes |
arguments | Chrome Full support 1 | Edge Full support 12 | Firefox Full support 1 | IE Full support 4 | Opera Full support 3 | Safari Full support 1 | WebView Android Full support 1 | Chrome Android Full support 18 | Firefox Android Full support 4 | Opera Android Full support 10.1 | Safari iOS Full support 1 | Samsung Internet Android Full support 1.0 | nodejs Full support Yes |
bind | Chrome Full support 7 | Edge Full support 12 | Firefox Full support 4 | IE Full support 9 | Opera Full support 11.6 | Safari Full support 5.1 | WebView Android Full support 4 | Chrome Android Full support 18 | Firefox Android Full support 4 | Opera Android Full support 12 | Safari iOS Full support 6 | Samsung Internet Android Full support 1.0 | nodejs Full support Yes |
call | Chrome Full support 1 | Edge Full support 12 | Firefox Full support 1 | IE Full support 5.5 | Opera Full support 4 | Safari Full support 1 | WebView Android Full support 1 | Chrome Android Full support 18 | Firefox Android Full support 4 | Opera Android Full support 10.1 | Safari iOS Full support 1 | Samsung Internet Android Full support 1.0 | nodejs Full support Yes |
caller | Chrome Full support 1 | Edge Full support 12 | Firefox Full support 1 | IE Full support 8 | Opera Full support 9.6 | Safari Full support 3 | WebView Android Full support 1 | Chrome Android Full support 18 | Firefox Android Full support 4 | Opera Android Full support 10.1 | Safari iOS Full support 1 | Samsung Internet Android Full support 1.0 | nodejs Full support Yes |
displayName | Chrome No support No | Edge No support No | Firefox Full support 13 | IE No support No | Opera No support No | Safari No support No | WebView Android No support No | Chrome Android No support No | Firefox Android Full support 14 | Opera Android No support No | Safari iOS No support No | Samsung Internet Android No support No | nodejs No support No |
length | Chrome Full support 1 | Edge Full support 12 | Firefox Full support 1 | IE Full support 4 | Opera Full support 3 | Safari Full support 1 | WebView Android Full support 1 | Chrome Android Full support 18 | Firefox Android Full support 4 | Opera Android Full support 10.1 | Safari iOS Full support 1 | Samsung Internet Android Full support 1.0 | nodejs Full support Yes |
name | Chrome Full support 15 | Edge Full support 14 | Firefox Full support 1 | IE No support No | Opera Full support 10.5 | Safari Full support 6 | WebView Android Full support 1 | Chrome Android Full support 18 | Firefox Android Full support 4 | Opera Android Full support 11 | Safari iOS Full support 6 | Samsung Internet Android Full support 1.0 | nodejs Full support Yes |
toSource | Chrome No support No | Edge No support No | Firefox
No support
1 — 74
| IE No support No | Opera No support No | Safari No support No | WebView Android No support No | Chrome Android No support No | Firefox Android Full support 4 | Opera Android No support No | Safari iOS No support No | Samsung Internet Android No support No | nodejs No support No |
toString | Chrome Full support 1 | Edge Full support 12 | Firefox Full support 1 | IE Full support 5 | Opera Full support 3 | Safari Full support 1 | WebView Android Full support 1 | Chrome Android Full support 18 | Firefox Android Full support 4 | Opera Android Full support 10.1 | Safari iOS Full support 1 | Samsung Internet Android Full support 1.0 | nodejs Full support Yes |
Legend
- Full support
- Full support
- No support
- No support
- Non-standard. Expect poor cross-browser support.
- Non-standard. Expect poor cross-browser support.
- Deprecated. Not for use in new websites.
- Deprecated. Not for use in new websites.
- See implementation notes.
- See implementation notes.
See also
- Functions and function scope
function
statementfunction
expressionfunction*
statementfunction*
expressionAsyncFunction
GeneratorFunction