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 of a given object's own enumerable property
[key, value]
pairs. 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 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 of a given object's own enumerable values.
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.
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. |
Living Standard | Added Object.entries, Object.values and Object.getOwnPropertyDescriptors. |
Browser compatibility
Feature | Chrome | Edge | Firefox (Gecko) | Internet Explorer | Opera | Safari |
---|---|---|---|---|---|---|
Basic support | (Yes) | (Yes) | (Yes) | (Yes) | (Yes) | (Yes) |
Feature | Android | Chrome for Android | Edge | Firefox Mobile (Gecko) | IE Mobile | Opera Mobile | Safari Mobile |
---|---|---|---|---|---|---|---|
Basic support | (Yes) | (Yes) | (Yes) | (Yes) | (Yes) | (Yes) | (Yes) |