Object

Table of Contents

  1. Summary
  2. Syntax
    1. Parameters
  3. Description
  4. Properties
  5. Methods
  6. Object instances
    1. Properties
    2. Methods
  7. Examples
    1. Example: Using Object given undefined and null types
    2. Example: Using Object to create Boolean objects
  8. Browser compatibility

Summary

Creates an object wrapper.

Syntax

new Object( [ value ] )

Parameters

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.

When called in a non-constructor context, Object behaves identically.

Properties

For properties available on Object instances, see Properties of Object instances.

prototype
Allows the addition of properties to all objects of type Object.
Properties inherited from Function:

Methods

For methods available on Object instances, see Methods of Object instances.
create Requires JavaScript 1.8.5
Creates a new object with the specified prototype object and properties.
defineProperty Requires JavaScript 1.8.5
Adds the named property described by a given descriptor to an object.
defineProperties Requires JavaScript 1.8.5
Adds the named properties described by the given descriptors to an object.
getOwnPropertyDescriptor Requires JavaScript 1.8.5
Returns a property descriptor for a named property on an object.
keys Requires JavaScript 1.8.5
Returns an array containing the names of all of the given object's own enumerable properties.
getOwnPropertyNames Requires JavaScript 1.8.5
Returns an array containing the names of all of the given object's own enumerable and non-enumerable properties.
getPrototypeOf Requires JavaScript 1.8.1
Returns the prototype of the specified object.
preventExtensions Requires JavaScript 1.8.5
Prevents any extensions of an object.
isExtensible Requires JavaScript 1.8.5
Determine if extending of an object is allowed.
seal Requires JavaScript 1.8.5
Prevents other code from deleting properties of an object.
is New in Firefox 22
Compares if two values are distingushiable (ie. the same)
isSealed Requires JavaScript 1.8.5
Determine if an object is sealed.
freeze Requires JavaScript 1.8.5
Freezes an object: other code can't delete or change any properties.
isFrozen Requires JavaScript 1.8.5
Determine if an object was frozen.
Methods inherited from Function:

Object instances

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

constructor
Specifies the function that creates an object's prototype.
__count__ Obsolete since JavaScript 1.8.5
Returns the number of enumerable properties directly on a user-defined object.
__parent__ Obsolete since JavaScript 1.8.5
Points to an object's context.
__proto__ Non-standard
Points to the object which was used as prototype when the object was instantiated.

Methods

__defineGetter__ Non-standard
Associates a function with a property that, when accessed, executes that function and returns its return value.
__defineSetter__ Non-standard
Associates a function with a property that, when set, executes that function which modifies the property.
eval Obsolete since JavaScript 1.8.5
Evaluates a string of JavaScript code in the context of the specified object.
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.
isPrototypeOf
Returns a boolean indication whether the specified object is in the prototype chain of the object this method is called upon.
__lookupGetter__ Non-standard
Returns the function associated with the specified property by the __defineGetter__ method.
__lookupSetter__ Non-standard
Returns the function associated with the specified property by the __defineSetter__ method.
__noSuchMethod__ Non-standard
Allows a function to be defined that will be executed when an undefined object member is called as a method.
propertyIsEnumerable
Returns a boolean indicating if the internal ECMAScript DontEnum attribute is set.
toSource Non-standard
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.
toLocaleString
Calls toString.
toString
Returns a string representation of the object.
unwatch Non-standard
Removes a watchpoint from a property of the object.
valueOf
Returns the primitive value of the specified object.
watch Non-standard
Adds a watchpoint to a property of the object.

Examples

Example: 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);

Example: 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());

Browser compatibility

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
Basic support (Yes) (Yes) ? ? ?
Feature Android Firefox Mobile (Gecko) IE Phone Opera Mobile Safari Mobile
Basic support ? (Yes) ? ? (Yes)

 

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