이 문서는 아직 자원 봉사자들이 한국어로 번역하지 않았습니다. 참여해서 번역을 마치도록 도와 주세요!
English (US)의 문서도 읽어보세요.

The toString() method returns a string representing the source code of the function.

Syntax

function.toString()

Return value

A string representing the source code of the function.

Description

The Function object overrides the toString method inherited from Object; it does not inherit 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. It will also throw for Proxy objects, for example.

Function.prototype.toString.call('foo'); // TypeError

var proxy = new Proxy(function() {}, {});
Function.prototype.toString.call(proxy); // TypeError

If the toString() method is called on built-in function objects or a function created by Function.prototype.bind, toString() returns a native function string which looks like

"function () {\n    [native code]\n}"

If the toString() method is called on a function created by the Function constructor, toString() returns the source code of a synthesized function declaration named "anonymous" using the provided parameters and function body.

Examples

Function Function.prototype.toString result
function f(){}
"function f(){}"
class A { a(){} }
"class A { a(){} }"
function* g(){}
"function* g(){}"
a => a
"a => a"
({ a(){} }.a)
"a(){}"
({ *a(){} }.a)
"*a(){}"
({ [0](){} }[0])
"[0](){}"
Object.getOwnPropertyDescriptor({
    get a(){}
}, "a").get
"get a(){}"
Object.getOwnPropertyDescriptor({
    set a(x){}
}, "a").set
"set a(x){}"
Function.prototype.toString
"function toString() { [native code] }"
(function f(){}.bind(0))
"function () { [native code] }"
Function("a", "b")
"function anonymous(a\n) {\nb\n}"

Specifications

Specification Status Comment
ECMAScript 1st Edition (ECMA-262) Standard Initial definition. Implemented in JavaScript 1.1.
ECMAScript 2015 (6th Edition, ECMA-262)
The definition of 'Function.prototype.toString' in that specification.
Standard Added more specific requirements for the string representation.
Function.prototype.toString revision Draft Standardizes native function string, line endings.
ECMAScript Latest Draft (ECMA-262)
The definition of 'Function.prototype.toString' in that specification.
Living Standard  

Browser compatibility

FeatureChromeEdgeFirefoxInternet ExplorerOperaSafari
Basic support Yes Yes Yes Yes Yes Yes
Support of toString revision No No54 No No No
FeatureAndroid webviewChrome for AndroidEdge mobileFirefox for AndroidIE mobileOpera AndroidiOS Safari
Basic support Yes Yes Yes Yes Yes Yes Yes
Support of toString revision No No No54 No No No

Firefox-specific notes

  • Since Firefox 17, Function.prototype.toString() has been implemented by saving the function's source. The decompiler was removed, so that the indentation parameter is not needed any more. See bug 761723 for more details.
  • Starting with Firefox 38, Function.prototype.toString() throws for Proxy objects (bug 1100936).

See also

문서 태그 및 공헌자

 최종 변경: michaelficarra,