This feature is obsolete. Although it may still work in some browsers, its use is discouraged since it could be removed at any time. Try to avoid using it.

The toSource() method returns a string representing the source code of the object.



Return value

A string representing the source code of the object.


The toSource() method returns the following values:

  • For the built-in Object object, toSource() returns the following string indicating that the source code is not available:
    function Object() {
        [native code]
  • For instances of Object, toSource() returns a string representing the source code.

You can call toSource() while debugging to examine the contents of an object.

Overriding the toSource() method

It is safe for objects to override the toSource() method. For example:

function Person(name) {
  this.name = name;

Person.prototype.toSource = function Person_toSource() {
  return 'new Person(' + uneval(this.name) + ')';

console.log(new Person('Joe').toSource()); // ---> new Person("Joe")

Built-in toSource() methods

Each core JavaScript type has its own toSource() method. These objects are:

Limitations on cyclical objects

In the case of objects that contain references to themselves, e.g. a cyclically linked list or a tree that can be traversed both ways, toSource() will not recreate the self-reference, as of Firefox 24. For example:

var obj1 = {};
var obj2 = { a: obj1 };
obj1.b = obj2;

console.log('Cyclical: ' + (obj1.b.a == obj1));

var objSource = obj1.toSource(); // returns "({b:{a:{}}})"

obj1 = eval(objSource);

console.log('Cyclical: ' + (obj1.b.a == obj1));

If a cyclical structure is employed and toSource() is needed, the object must provide an override to toSource(), either using a reference to a constructor or providing an anonymous function.


Using toSource()

The following code defines the Dog object type and creates theDog, an object of type Dog:

function Dog(name, breed, color, sex) {
  this.name = name;
  this.breed = breed;
  this.color = color;
  this.sex = sex;

theDog = new Dog('Gabby', 'Lab', 'chocolate', 'female');

Calling the toSource() method of theDog displays the JavaScript source that defines the object:

// returns ({name:"Gabby", breed:"Lab", color:"chocolate", sex:"female"})


Not part of any standard.

Browser compatibility

ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung InternetNode.js
Chrome No support NoEdge No support NoFirefox No support 1 — 74
No support 1 — 74
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 NoOpera No support NoSafari No support NoWebView Android No support NoChrome Android No support NoFirefox Android Full support 4Opera Android No support NoSafari iOS No support NoSamsung Internet Android No support Nonodejs No support No


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