The Function
object provides methods for functions. In JavaScript, every function is actually a Function
object.
The Function
object provides methods for functions. In JavaScript, every function is actually a Function
object.
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.
These properties are defined on Function.prototype
and shared by all Function
instances.
Function.prototype.arguments
Deprecated Non-standard
Represents the arguments passed to this function. For strict, arrow, async, and generator functions, accessing the arguments
property throws a TypeError
. Use the arguments
object inside function closures instead.
Function.prototype.caller
Deprecated Non-standard
Represents the function that invoked this function. For strict, arrow, async, and generator functions, accessing the caller
property throws a TypeError
.
Function.prototype.constructor
The constructor function that created the instance object. For Function
instances, the initial value is the Function
constructor.
These properties are own properties of each Function
instance.
displayName
Non-standard Optional
The display name of the function.
length
Specifies the number of arguments expected by the function.
name
The name of the function.
prototype
Used when the function is used as a constructor with the new
operator. It will become the new object's prototype.
Function.prototype.apply()
Calls a function with a given this
value and optional arguments provided as an array (or an array-like object).
Function.prototype.bind()
Creates a new function that, when called, has its this
keyword set to a provided value, optionally with a given sequence of arguments preceding any provided when the new function is called.
Function.prototype.call()
Calls a function with a given this
value and optional arguments.
Function.prototype.toString()
Returns a string representing the source code of the function. Overrides the Object.prototype.toString
method.
Function.prototype[@@hasInstance]()
Specifies the default procedure for determining if a constructor function recognizes an object as one of the constructor's instances. Called by the instanceof
operator.
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.
// Create a global property with `var` var x = 10; function createFunction1() { const x = 20; return new Function("return x;"); // this `x` refers to global `x` } function createFunction2() { const x = 20; function f() { return x; // this `x` refers to the local `x` above } return f; } const f1 = createFunction1(); console.log(f1()); // 10 const 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.
Specification |
---|
ECMAScript Language Specification # sec-function-objects |
Desktop | Mobile | Server | ||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Chrome | Edge | Firefox | Opera | Safari | Chrome Android | Firefox for Android | Opera Android | Safari on IOS | Samsung Internet | WebView Android | Deno | Node.js | ||
@@hasInstance |
50 | 15 | 50 | 37 | 10 | 50 | 50 | 37 | 10 | 5.0 | 50 | 1.0 | 6.5.0 | |
Function |
1 | 12 | 1 | 3 | 1 | 18 | 4 | 10.1 | 1 | 1.0 | 4.4 | 1.0 | 0.10.0 | |
Function |
1 | 12 | 1 | 3 | 1 | 18 | 4 | 10.1 | 1 | 1.0 | ≤37 | 1.0 | 0.10.0 | |
apply |
1 | 12 | 1 | 4 | 1 | 18 | 4 | 10.1 | 1 | 1.0 | 4.4 | 1.0 | 0.10.0 | |
arguments |
1 | 12 | 1 | 3 | 1 | 18 | 4 | 10.1 | 1 | 1.0 | 4.4 | 1.0 | 0.10.0 | |
bind |
7 | 12 | 4 | 11.6 | 5.1 | 18 | 4 | 12 | 6 | 1.0 | 4 | 1.0 | 0.10.0 | |
call |
1 | 12 | 1 | 4 | 1 | 18 | 4 | 10.1 | 1 | 1.0 | 4.4 | 1.0 | 0.10.0When calling this method,thisArg does not default to the global object. |
|
caller |
1 | 12 | 1 | 9.6 | 3 | 18 | 4 | 10.1 | 1 | 1.0 | 4.4 | 1.0 | 0.10.0 | |
displayName |
No | No | 13 | No | No | No | 14 | No | No | No | No | No | No | |
length |
1 | 12 | 1 | 3 | 1 | 18 | 4 | 10.1 | 1 | 1.0 | 4.4 | 1.0 | 0.10.0 | |
name |
15 | 14 | 1 | 10.5 | 6 | 18 | 4 | 11 | 6 | 1.0 | 4.4 | 1.0 | 0.10.0 | |
toString |
1 | 12 | 1 | 3 | 1 | 18 | 4 | 10.1 | 1 | 1.0 | 4.4 | 1.0 | 0.10.0 |
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https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function