Web/JavaScript/Reference/Global objects/Object

The Object class represents one of JavaScript's data types. It is used to store various keyed collections and more complex entities. Objects can be created using the Object() constructor or the object initializer / literal syntax.

Description

Nearly all objects in JavaScript are instances of Object; a typical object inherits properties (including methods) from Object.prototype, although these properties may be shadowed (a.k.a. overridden). However, an Object may be deliberately created for which this is not true (e.g. by Object.create(null)), or it may be altered so that this is no longer true (e.g. with Object.setPrototypeOf).

Changes to the Object prototype object are seen by all objects through prototype chaining, unless the properties and methods subject to those changes are overridden further along the prototype chain. This provides a very powerful although potentially dangerous mechanism to override or extend object behavior.

The Object constructor creates an object wrapper for the given value.

If the value is null or undefined, it will create and return an empty object.
Otherwise, it will return an object of a Type that corresponds to the given value.
If the value is an object already, it will return the value.

When called in a non-constructor context, Object behaves identically to new Object().

Deleting a property from an object

There isn't any method in an Object itself to delete its own properties (such as Map.prototype.delete()). To do so, one must use the delete operator.

Constructor

Object(): Creates a new Object object. It is a wrapper for the given value.

Static methods

Object.assign(): Copies the values of all enumerable own properties from one or more source objects to a target object.
Object.create(): Creates a new object with the specified prototype object and properties.
Object.defineProperty(): Adds the named property described by a given descriptor to an object.
Object.defineProperties(): Adds the named properties described by the given descriptors to an object.
Object.entries(): Returns an array containing all of the [key, value] pairs of a given object's own enumerable string properties.
Object.freeze(): Freezes an object. Other code cannot delete or change its properties.
Object.fromEntries(): Returns a new object from an iterable of [key, value] pairs. (This is the reverse of Object.entries).
Object.getOwnPropertyDescriptor(): Returns a property descriptor for a named property on an object.
Object.getOwnPropertyDescriptors(): Returns an object containing all own property descriptors for an object.
Object.getOwnPropertyNames(): Returns an array containing the names of all of the given object's own enumerable and non-enumerable properties.
Object.getOwnPropertySymbols(): Returns an array of all symbol properties found directly upon a given object.
Object.getPrototypeOf(): Returns the prototype (internal Web/JavaScript/Reference/Global objects/Prototype property) of the specified object.
Object.is(): Compares if two values are the same value. Equates all NaN values (which differs from both Abstract Equality Comparison and Strict Equality Comparison).
Object.isExtensible(): Determines if extending of an object is allowed.
Object.isFrozen(): Determines if an object was frozen.
Object.isSealed(): Determines if an object is sealed.
Object.keys(): Returns an array containing the names of all of the given object's own enumerable string properties.
Object.preventExtensions(): Prevents any extensions of an object.
Object.seal(): Prevents other code from deleting properties of an object.
Object.setPrototypeOf(): Sets the object's prototype (its internal Web/JavaScript/Reference/Global objects/Prototype property).
Object.values(): Returns an array containing the values that correspond to all of a given object's own enumerable string properties.

Instance properties

Object.prototype.constructor: Specifies the function that creates an object's prototype.
Object.prototype.__proto__: Points to the object which was used as prototype when the object was instantiated.
[[../../../../../Archive/Web/JavaScript/Object-2|Object.prototype.__noSuchMethod__]]: Allows a function to be defined that will be executed when an undefined object member is called as a method.

Instance methods

Object.prototype.__defineGetter__(): Associates a function with a property that, when accessed, executes that function and returns its return value.
Object.prototype.__defineSetter__(): Associates a function with a property that, when set, executes that function which modifies the property.
Object.prototype.__lookupGetter__(): Returns the function associated with the specified property by the __defineGetter__() method.
Object.prototype.__lookupSetter__(): Returns the function associated with the specified property by the __defineSetter__() method.
Object.prototype.hasOwnProperty(): Returns a boolean indicating whether an object contains the specified property as a direct property of that object and not inherited through the prototype chain.
Object.prototype.isPrototypeOf(): Returns a boolean indicating whether the object this method is called upon is in the prototype chain of the specified object.
Object.prototype.propertyIsEnumerable(): Returns a boolean indicating if the internal [[Web/JavaScript/Data_structures#Properties|ECMAScript Enumerable attribute]] is set.
Object.prototype.toLocaleString(): Calls toString().
Object.prototype.toString(): Returns a string representation of the object.
[[../../../../../Archive/Web/JavaScript/Object-4|Object.prototype.unwatch()]]: Removes a watchpoint from a property of the object.
Object.prototype.valueOf(): Returns the primitive value of the specified object.
[[../../../../../Archive/Web/JavaScript/Object-5|Object.prototype.watch()]]: Adds a watchpoint to a property of the object.

Examples

Using `Object` given `undefined` and `null` types

The following examples store an empty Object object in o:

let o = new Object()

let o = new Object(undefined)

let o = new Object(null)

Using `Object` to create `Boolean` objects

The following examples store Boolean objects in o:

// equivalent to o = new Boolean(true)
let o = new Object(true)

// equivalent to o = new Boolean(false)
let o = new Object(Boolean())

Object prototypes

When altering the behavior of existing Object.prototype methods, consider injecting code by wrapping your extension before or after the existing logic. For example, this (untested) code will pre-conditionally execute custom logic before the built-in logic or someone else's extension is executed.

When a function is called, the arguments to the call are held in the array-like "variable" arguments. For example, in the call myFn(a, b, c), the arguments within myFn's body will contain 3 array-like elements corresponding to (a, b, c).

When modifying prototypes with hooks, pass this and the arguments (the call state) to the current behavior by calling apply() on the function. This pattern can be used for any prototype, such as Node.prototype, Function.prototype, etc.

var current = Object.prototype.valueOf;

// Since my property "-prop-value" is cross-cutting and isn't always
// on the same prototype chain, I want to modify Object.prototype: 
Object.prototype.valueOf = function() {
  if (this.hasOwnProperty('-prop-value')) {
    return this['-prop-value'];
  } else {
    // It doesn't look like one of my objects, so let's fall back on 
    // the default behavior by reproducing the current behavior as best we can.
    // The apply behaves like "super" in some other languages.
    // Even though valueOf() doesn't take arguments, some other hook may.
    return current.apply(this, arguments);
  }
}

Since JavaScript doesn't exactly have sub-class objects, prototype is a useful workaround to make a “base class” object of certain functions that act as objects. For example:

var Person = function(name) {
  this.name = name;
  this.canTalk = true;
};

Person.prototype.greet = function() {
  if (this.canTalk) {
    console.log('Hi, I am ' + this.name);
  }
};

var Employee = function(name, title) {
  Person.call(this, name);
  this.title = title;
};

Employee.prototype = Object.create(Person.prototype);
Employee.prototype.constructor = Employee; //If you don't set Object.prototype.constructor to Employee, 
                                           //it will take prototype.constructor of Person (parent). 
                                           //To avoid that, we set the prototype.constructor to Employee (child).


Employee.prototype.greet = function() {
  if (this.canTalk) {
    console.log('Hi, I am ' + this.name + ', the ' + this.title);
  }
};

var Customer = function(name) {
  Person.call(this, name);
};

Customer.prototype = Object.create(Person.prototype);
Customer.prototype.constructor = Customer; //If you don't set Object.prototype.constructor to Customer, 
                                           //it will take prototype.constructor of Person (parent). 
                                           //To avoid that, we set the prototype.constructor to Customer (child).


var Mime = function(name) {
  Person.call(this, name);
  this.canTalk = false;
};

Mime.prototype = Object.create(Person.prototype);
Mime.prototype.constructor = Mime; //If you don't set Object.prototype.constructor to Mime,
                                   //it will take prototype.constructor of Person (parent).
                                   //To avoid that, we set the prototype.constructor to Mime (child).


var bob = new Employee('Bob', 'Builder');
var joe = new Customer('Joe');
var rg = new Employee('Red Green', 'Handyman');
var mike = new Customer('Mike');
var mime = new Mime('Mime');

bob.greet();
// Hi, I am Bob, the Builder

joe.greet();
// Hi, I am Joe

rg.greet();
// Hi, I am Red Green, the Handyman

mike.greet();
// Hi, I am Mike

mime.greet();

Specifications

Specification
ECMAScript (ECMA-262)The definition of 'Object' 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
`Object`	Chrome Full support 1	Edge Full support 12	Firefox Full support 1	IE Full support 3	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
`Object()` constructor	Chrome Full support 1	Edge Full support 12	Firefox Full support 1	IE Full support 3	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
`assign`	Chrome Full support 45	Edge Full support 12	Firefox Full support 34	IE No support No	Opera Full support 32	Safari Full support 9	WebView Android Full support 45	Chrome Android Full support 45	Firefox Android Full support 34	Opera Android Full support 32	Safari iOS Full support 9	Samsung Internet Android Full support 5.0	nodejs Full support 4.0.0
`constructor`	Chrome Full support 1	Edge Full support 12	Firefox Full support 1	IE Full support 4	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
`create`	Chrome Full support 5	Edge Full support 12	Firefox Full support 4	IE Full support 9	Opera Full support 11.6	Safari Full support 5	WebView Android Full support 1	Chrome Android Full support 18	Firefox Android Full support 4	Opera Android Full support 12	Safari iOS Full support 5	Samsung Internet Android Full support 1.0	nodejs Full support Yes
`__defineGetter__` Deprecated'	Chrome Full support 1	Edge Full support 12	Firefox Full support 1 Notes' Full support 1 Notes' Notes' Starting with Firefox 48, this method can no longer be called at the global scope without any object. A `TypeError` will be thrown otherwise. Previously, the global object was used in these cases automatically, but this is no longer the case.	IE Full support 11	Opera Full support 9.5	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
`defineProperties`	Chrome Full support 5	Edge Full support 12	Firefox Full support 4	IE Full support 9	Opera Full support 11.6	Safari Full support 5	WebView Android Full support 1	Chrome Android Full support 18	Firefox Android Full support 4	Opera Android Full support 12	Safari iOS Full support 5	Samsung Internet Android Full support 1.0	nodejs Full support Yes
`defineProperty`	Chrome Full support 5	Edge Full support 12	Firefox Full support 4	IE Full support 9 Full support 9 Partial support 8 Notes' Notes' In Internet Explorer 8, this was only supported on DOM objects and with some non-standard behaviors. This was later fixed in Internet Explorer 9.	Opera Full support 11.6	Safari Full support 5.1 Notes' Full support 5.1 Notes' Notes' Also supported in Safari 5, but not on DOM objects.	WebView Android Full support 1	Chrome Android Full support 18	Firefox Android Full support 4	Opera Android Full support 12	Safari iOS Full support 6 Notes' Full support 6 Notes' Notes' Also supported in Safari for iOS 4.2, but not on DOM objects.	Samsung Internet Android Full support 1.0	nodejs Full support Yes
`__defineSetter__` Deprecated'	Chrome Full support 1	Edge Full support 12	Firefox Full support 1 Notes' Full support 1 Notes' Notes' Starting with Firefox 48, this method can no longer be called at the global scope without any object. A `TypeError` will be thrown otherwise. Previously, the global object was used in these cases automatically, but this is no longer the case.	IE Full support 11	Opera Full support 9.5	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
`entries`	Chrome Full support 54	Edge Full support 14	Firefox Full support 47	IE No support No	Opera Full support 41	Safari Full support 10.1	WebView Android Full support 54	Chrome Android Full support 54	Firefox Android Full support 47	Opera Android Full support 41	Safari iOS Full support 10.3	Samsung Internet Android Full support 6.0	nodejs Full support 7.0.0 Full support 7.0.0 Full support 6.5.0 Disabled' Disabled' From version 6.5.0: this feature is behind the `--harmony` runtime flag.
`freeze`	Chrome Full support 6	Edge Full support 12	Firefox Full support 4	IE Full support 9	Opera Full support 12	Safari Full support 5.1	WebView Android Full support 1	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
`fromEntries`	Chrome Full support 73	Edge Full support 79	Firefox Full support 63	IE No support No	Opera Full support 60	Safari Full support 12.1	WebView Android Full support 73	Chrome Android Full support 73	Firefox Android Full support 63	Opera Android No support No	Safari iOS Full support 12.2	Samsung Internet Android No support No	nodejs Full support 12.0.0
`getOwnPropertyDescriptor`	Chrome Full support 5	Edge Full support 12	Firefox Full support 4	IE Full support 9 Full support 9 Partial support 8 Notes' Notes' In Internet Explorer 8, this was only supported on DOM objects and with some non-standard behaviors. This was later fixed in Internet Explorer 9.	Opera Full support 12	Safari Full support 5	WebView Android Full support 1	Chrome Android Full support 18	Firefox Android Full support 4	Opera Android Full support 12	Safari iOS Full support 5	Samsung Internet Android Full support 1.0	nodejs Full support Yes
`getOwnPropertyDescriptors`	Chrome Full support 54	Edge Full support 15	Firefox Full support 50	IE No support No	Opera Full support 41	Safari Full support 10	WebView Android Full support 54	Chrome Android Full support 54	Firefox Android Full support 50	Opera Android Full support 41	Safari iOS Full support 10	Samsung Internet Android Full support 6.0	nodejs Full support 7.0.0 Full support 7.0.0 Full support 6.5.0 Disabled' Disabled' From version 6.5.0: this feature is behind the `--harmony` runtime flag.
`getOwnPropertyNames`	Chrome Full support 5	Edge Full support 12	Firefox Full support 4	IE Full support 9	Opera Full support 12	Safari Full support 5	WebView Android Full support 1	Chrome Android Full support 18	Firefox Android Full support 4	Opera Android Full support 12	Safari iOS Full support 5	Samsung Internet Android Full support 1.0	nodejs Full support Yes
`getOwnPropertySymbols`	Chrome Full support 38	Edge Full support 12	Firefox Full support 36	IE No support No	Opera Full support 25	Safari Full support 9	WebView Android Full support 38	Chrome Android Full support 38	Firefox Android Full support 36	Opera Android Full support 25	Safari iOS Full support 9	Samsung Internet Android Full support 3.0	nodejs Full support 0.12
`getPrototypeOf`	Chrome Full support 5	Edge Full support 12	Firefox Full support 3.5	IE Full support 9	Opera Full support 12.1	Safari Full support 5	WebView Android Full support 1	Chrome Android Full support 18	Firefox Android Full support 4	Opera Android Full support 12.1	Safari iOS Full support 5	Samsung Internet Android Full support 1.0	nodejs Full support Yes
`hasOwnProperty`	Chrome Full support 1	Edge Full support 12	Firefox Full support 1	IE Full support 5.5	Opera Full support 5	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
`is`	Chrome Full support 30	Edge Full support 12	Firefox Full support 22	IE No support No	Opera Full support 17	Safari Full support 9	WebView Android Full support ≤37	Chrome Android Full support 30	Firefox Android Full support 22	Opera Android Full support 18	Safari iOS Full support 9	Samsung Internet Android Full support 2.0	nodejs Full support 0.10
`isExtensible`	Chrome Full support 6	Edge Full support 12	Firefox Full support 4	IE Full support 9	Opera Full support 12	Safari Full support 5.1	WebView Android Full support 1	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
`isFrozen`	Chrome Full support 6	Edge Full support 12	Firefox Full support 4	IE Full support 9	Opera Full support 12	Safari Full support 5.1	WebView Android Full support 1	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
`isPrototypeOf`	Chrome Full support 1	Edge Full support 12	Firefox Full support 1	IE Full support 9	Opera Full support 4	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
`isSealed`	Chrome Full support 6	Edge Full support 12	Firefox Full support 4	IE Full support 9	Opera Full support 12	Safari Full support 5.1	WebView Android Full support 1	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
`keys`	Chrome Full support 5	Edge Full support 12	Firefox Full support 4	IE Full support 9	Opera Full support 12	Safari Full support 5	WebView Android Full support 1	Chrome Android Full support 18	Firefox Android Full support 4	Opera Android Full support 12	Safari iOS Full support 5	Samsung Internet Android Full support 1.0	nodejs Full support Yes
`__lookupGetter__` Deprecated'	Chrome Full support 1	Edge Full support 12	Firefox Full support 1	IE Full support 11	Opera Full support 9.5	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
`__lookupSetter__` Deprecated'	Chrome Full support 1	Edge Full support 12	Firefox Full support 1	IE Full support 11	Opera Full support 9.5	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
`preventExtensions`	Chrome Full support 6	Edge Full support 12	Firefox Full support 4	IE Full support 9	Opera Full support 12	Safari Full support 5.1	WebView Android Full support 1	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
`propertyIsEnumerable`	Chrome Full support 1	Edge Full support 12	Firefox Full support 1	IE Full support 5.5	Opera Full support 4	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
`__proto__` Deprecated'	Chrome Full support 1	Edge Full support 12	Firefox Full support 1	IE Full support 11	Opera Full support 10.5	Safari Full support 3	WebView Android Full support 1	Chrome Android Full support 18	Firefox Android Full support 4	Opera Android Full support 11	Safari iOS Full support 1	Samsung Internet Android Full support 1.0	nodejs Full support Yes
`seal`	Chrome Full support 6	Edge Full support 12	Firefox Full support 4	IE Full support 9	Opera Full support 12	Safari Full support 5.1	WebView Android Full support 1	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
`setPrototypeOf`	Chrome Full support 34	Edge Full support 12	Firefox Full support 31	IE Full support 11	Opera Full support 21	Safari Full support 9	WebView Android Full support 37	Chrome Android Full support 34	Firefox Android Full support 31	Opera Android Full support 21	Safari iOS Full support 9	Samsung Internet Android Full support 2.0	nodejs Full support 0.12
`toLocaleString`	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
`toSource` Deprecated'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 3	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
`valueOf`	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
`values`	Chrome Full support 54	Edge Full support 14	Firefox Full support 47	IE No support No	Opera Full support 41	Safari Full support 10.1	WebView Android Full support 54	Chrome Android Full support 54	Firefox Android Full support 47	Opera Android Full support 41	Safari iOS Full support 10.3	Samsung Internet Android Full support 6.0	nodejs Full support 7.0.0 Full support 7.0.0 Full support 6.5.0 Disabled' Disabled' From version 6.5.0: this feature is behind the `--harmony` runtime flag.

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.
User must explicitly enable this feature.': User must explicitly enable this feature.

Web/JavaScript/Reference/Global objects/Object

Contents

Description

Deleting a property from an object

Constructor

Static methods

Instance properties

Instance methods

Examples

Using `Object` given `undefined` and `null` types

Using `Object` to create `Boolean` objects

Object prototypes

Specifications

Browser compatibility

Legend

See also

Web/JavaScript/Reference/Global objects/Object

Description

Deleting a property from an object

Constructor

Static methods

Instance properties

Instance methods

Examples

Using Object given undefined and null types

Using Object to create Boolean objects

Object prototypes

Specifications

Browser compatibility

Legend

See also

Using `Object` given `undefined` and `null` types

Using `Object` to create `Boolean` objects