Web/JavaScript/Reference/Global objects/Function

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 to eval. However, unlike eval, the Function 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 of Function. Use the arguments 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 provided thisArg. Arguments can be passed as an Array object.
Function.prototype.bind(thisArg[, arg1[, arg2[, ...argN])]]: Creates a new function which, when called, has its this set to the provided thisArg. 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 the Object.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

Update compatibility data on GitHub

	Desktop						Mobile						Server
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet	Node.js
`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` Deprecated'Non-standard'	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` Non-standard'	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` Non-standard'	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` Non-standard'	Chrome No support No	Edge No support No	Firefox No support 1 — 74 Notes' No support 1 — 74 Notes' Notes' Starting in Firefox 74, `toSource()` is no longer available for use by web content. It is still allowed for internal and privileged code.	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.