Object

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.fromEntries()

Returns a new object from an iterable of key-value pairs (reverses 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 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

Methods

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

Browser compatibility

See also

• Object initializer