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The Object constructor creates an object wrapper.

Syntax

// Object initialiser or literal
{ [ nameValuePair1[, nameValuePair2[, ...nameValuePairN] ] ] }

// Called as a constructor
new Object([value])

Parameters

nameValuePair1, nameValuePair2, ... nameValuePairN
Pairs of names (strings) and values (any value) where the name is separated from the value by a colon.
value
Any value.

Description

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().

See also the object initializer / literal syntax.

Properties of the Object constructor

Object.length
Has a value of 1.
Object.prototype
Allows the addition of properties to all objects of type Object.

Methods of the Object constructor

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 can't delete or change any properties.
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 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 prototype (i.e., the internal [[Prototype]] property)
Object.values()
Returns an array containing the values that correspond to all of a given object's own enumerable string properties.

Object instances and Object prototype object

All objects in JavaScript are descended from Object; all objects inherit methods and properties from Object.prototype, although they may be overridden. For example, other constructors' prototypes override the constructor property and provide their own toString() methods. Changes to the Object prototype object are propagated to all objects unless the properties and methods subject to those changes are overridden further along the prototype chain.

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.
Object.prototype.__noSuchMethod__
Allows a function to be defined that will be executed when an undefined object member is called as a method.
Object.prototype.__count__
Used to return the number of enumerable properties directly on a user-defined object, but has been removed.
Object.prototype.__parent__
Used to point to an object's context, but has been removed.

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 ECMAScript [[Enumerable]] attribute is set.
Object.prototype.toSource()
Returns string containing the source of an object literal representing the object that this method is called upon; you can use this value to create a new object.
Object.prototype.toLocaleString()
Calls toString().
Object.prototype.toString()
Returns a string representation of the object.
Object.prototype.unwatch()
Removes a watchpoint from a property of the object.
Object.prototype.valueOf()
Returns the primitive value of the specified object.
Object.prototype.watch()
Adds a watchpoint to a property of the object.
Object.prototype.eval()
Used to evaluate a string of JavaScript code in the context of the specified object, but has been removed.

Deleting a property from an object

There isn't any method in an Object itself to delete its own properties (e.g. like Map.prototype.delete()). To do so one has to use the delete operator.

Examples

Using Object given undefined and null types

The following examples store an empty Object object in o:

var o = new Object();
var o = new Object(undefined);
var o = new Object(null);

Using Object to create Boolean objects

The following examples store Boolean objects in o:

// equivalent to o = new Boolean(true);
var o = new Object(true);
// equivalent to o = new Boolean(false);
var o = new Object(Boolean());

Specifications

Specification Status Comment
ECMAScript 1st Edition (ECMA-262) Standard Initial definition. Implemented in JavaScript 1.0.
ECMAScript 5.1 (ECMA-262)
The definition of 'Object' in that specification.
Standard  
ECMAScript 2015 (6th Edition, ECMA-262)
The definition of 'Object' in that specification.
Standard Added Object.assign, Object.getOwnPropertySymbols, Object.setPrototypeOf, Object.is
ECMAScript Latest Draft (ECMA-262)
The definition of 'Object' in that specification.
Draft Added Object.entries, Object.values and Object.getOwnPropertyDescriptors.

Browser compatibility

FeatureChromeEdgeFirefoxInternet ExplorerOperaSafari
Basic support Yes Yes1 Yes Yes Yes
prototype Yes Yes1 Yes Yes Yes
__count__ No No No No No No
__noSuchMethod__ No No1 — 43 No No No
__parent__ No No No No No No
__proto__ Yes Yes111 Yes Yes
constructor Yes Yes1 Yes Yes Yes
assign45 Yes34 No329
create5 Yes4911.65
defineProperties5 Yes4911.65
defineProperty5 Yes49111.65.12
entries54 Yes47 No4110.1
freeze6 Yes49125.1
getNotifier36 — 52 No No No No No
getOwnPropertyDescriptor5 Yes48125
getOwnPropertyDescriptors54 Yes50 No4110
getOwnPropertyNames5 Yes49125
getOwnPropertySymbols38 Yes36 No259
getPrototypeOf5 Yes3.5912.15
is30 Yes22 No Yes9
isExtensible6 Yes49125.1
isFrozen6 Yes49125.1
isSealed6 Yes49125.1
keys5 Yes49125
observe36 — 52 No No No No No
preventExtensions6 Yes49125.1
__defineGetter__ Yes Yes1311 Yes Yes
__defineSetter__ Yes Yes1311 Yes Yes
__lookupGetter__ Yes Yes111 Yes Yes
__lookupSetter__ Yes Yes111 Yes Yes
eval No No No No No No
hasOwnProperty Yes Yes1 Yes Yes Yes
isPrototypeOf Yes Yes Yes Yes Yes Yes
propertyIsEnumerable Yes Yes Yes Yes Yes Yes
toLocaleString Yes Yes1 Yes Yes Yes
toSource No No1 No No No
toString Yes Yes1 Yes Yes Yes
unwatch No No1 — 58 No No No
valueOf Yes Yes1 Yes Yes Yes
watch No No1 — 58 No No No
seal6 Yes49125.1
setPrototypeOf34 Yes3111 Yes9
unobserve36 — 52 No No No No No
values54 Yes47 No4110.1
FeatureAndroid webviewChrome for AndroidEdge mobileFirefox for AndroidOpera AndroidiOS SafariSamsung Internet
Basic support Yes Yes Yes4 Yes Yes Yes
prototype Yes Yes Yes4 Yes Yes Yes
__count__ No No No No No No No
__noSuchMethod__ No No No4 — 43 No No No
__parent__ No No No No No No No
__proto__ Yes Yes Yes4 Yes Yes Yes
constructor Yes Yes Yes4 Yes Yes Yes
assign No45 Yes34 No Yes5.0
create Yes Yes Yes411.5 Yes Yes
defineProperties Yes Yes Yes411.5 Yes Yes
defineProperty Yes Yes Yes411.5 Yes Yes
entries5454 Yes4741 No6.0
freeze Yes Yes Yes4 Yes Yes Yes
getNotifier No No No No No No No
getOwnPropertyDescriptor Yes Yes Yes4 Yes Yes Yes
getOwnPropertyDescriptors ?54 Yes50 ? ?6.0
getOwnPropertyNames Yes Yes Yes4 Yes Yes Yes
getOwnPropertySymbols5.138 Yes36259 Yes
getPrototypeOf Yes Yes Yes4 Yes Yes Yes
is Yes Yes Yes22 Yes9 Yes
isExtensible Yes Yes Yes4 Yes Yes Yes
isFrozen Yes Yes Yes4 Yes Yes Yes
isSealed Yes Yes Yes4 Yes Yes Yes
keys Yes Yes Yes4 Yes Yes Yes
observe No No No No No No No
preventExtensions Yes Yes Yes4 Yes Yes Yes
__defineGetter__ Yes Yes Yes4 Yes Yes Yes
__defineSetter__ Yes Yes Yes4 Yes Yes Yes
__lookupGetter__ Yes Yes Yes4 Yes Yes Yes
__lookupSetter__ Yes Yes Yes4 Yes Yes Yes
eval No No No No No No No
hasOwnProperty Yes Yes Yes4 Yes Yes Yes
isPrototypeOf Yes Yes Yes Yes Yes Yes Yes
propertyIsEnumerable Yes Yes Yes Yes Yes Yes Yes
toLocaleString Yes Yes Yes4 Yes Yes Yes
toSource No No No4 No No No
toString Yes Yes Yes4 Yes Yes Yes
unwatch No No No4 — 58 No No No
valueOf Yes Yes Yes4 Yes Yes Yes
watch No No No4 — 58 No No No
seal Yes Yes Yes4 Yes Yes Yes
setPrototypeOf Yes Yes Yes31 Yes Yes Yes
unobserve No No No No No No No
values5454 Yes474110.36.0

1. Also supported in Internet Explorer 8, but only on DOM objects and with some non-standard behaviors.

2. Also supported in Safari 5, but not on DOM objects.

3. 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.

See also

Document Tags and Contributors

 Contributors to this page: rwaldron
 Last updated by: rwaldron,