Object 建構式可用於建立物件包裝(object wrapper)。


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

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


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


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().

也可以參考 object initializer / literal syntax.

Object 建構式屬性

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

Object 建構式方法

Creates a new object by copying the values of all enumerable own properties from one or more source objects to a target object.
Creates a new object with the specified prototype object and properties.
Adds the named property described by a given descriptor to an object.
Adds the named properties described by the given descriptors to an object.
Object.entries() (en-US)
Returns an array of a given object's own enumerable property [key, value] pairs.
Freezes an object: other code can't delete or change any properties.
Object.getOwnPropertyDescriptor() (en-US)
Returns a property descriptor for a named property on an object.
Object.getOwnPropertyDescriptors() (en-US)
Returns an object containing all own property descriptors for an object.
Object.getOwnPropertyNames() (en-US)
Returns an array containing the names of all of the given object's own enumerable and non-enumerable properties.
Object.getOwnPropertySymbols() (en-US)
Returns an array of all symbol properties found directly upon a given object.
Returns the prototype of the specified object.
Object.is() (en-US)
Compares if two values are distinguishable (ie. the same)
Object.isExtensible() (en-US)
Determines if extending of an object is allowed.
Object.isFrozen() (en-US)
Determines if an object was frozen.
Object.isSealed() (en-US)
Determines if an object is sealed.
Returns an array containing the names of all of the given object's own enumerable properties.
Prevents any extensions of an object.
Object.seal() (en-US)
Prevents other code from deleting properties of an object.
Object.setPrototypeOf() (en-US)
Sets the prototype (i.e., the internal [[Prototype]] property)
Object.values() (en-US)
Returns an array of a given object's own enumerable values.

Object 物件實體與 Object 原型物件

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.


Object.prototype.constructor (en-US)
Specifies the function that creates an object's prototype.
Object.prototype.__proto__ (en-US)
Points to the object which was used as prototype when the object was instantiated.
Allows a function to be defined that will be executed when an undefined object member is called as a method.
Object.prototype.__count__ This is an obsolete API and is no longer guaranteed to work.
Used to return the number of enumerable properties directly on a user-defined object, but has been removed.
Object.prototype.__parent__ This is an obsolete API and is no longer guaranteed to work.
Used to point to an object's context, but has been removed.


Object.prototype.__defineGetter__() (en-US)
Associates a function with a property that, when accessed, executes that function and returns its return value.
Object.prototype.__defineSetter__() (en-US)
Associates a function with a property that, when set, executes that function which modifies the property.
Object.prototype.__lookupGetter__() (en-US)
Returns the function associated with the specified property by the __defineGetter__ (en-US) method.
Object.prototype.__lookupSetter__() (en-US)
Returns the function associated with the specified property by the __defineSetter__ (en-US) method.
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() (en-US)
Returns a boolean indication whether the specified object is in the prototype chain of the object this method is called upon.
Object.prototype.propertyIsEnumerable() (en-US)
Returns a boolean indicating if the internal ECMAScript DontEnum attribute is set.
Object.prototype.toSource() (en-US)
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() (en-US)
Calls toString() (en-US).
Object.prototype.toString() (en-US)
Returns a string representation of the object.
Removes a watchpoint from a property of the object.
Object.prototype.valueOf() (en-US)
Returns the primitive value of the specified object.
Adds a watchpoint to a property of the object.
Object.prototype.eval() This is an obsolete API and is no longer guaranteed to work.
Used to evaluate a string of JavaScript code in the context of the specified object, but has been removed.


Using Object given undefined and null types


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

Using Object to create Boolean objects

下面例子儲存 Boolean 物件在 o:

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


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.
ECMAScript 2015 (6th Edition, ECMA-262)
The definition of 'Object' in that specification.
Standard Added Object.assign, Object.getOwnPropertySymbols, Object.setPrototypeOf, Object.is
ECMAScript (ECMA-262)
The definition of 'Object' in that specification.
Living Standard Added Object.entries, Object.values and Object.getOwnPropertyDescriptors.


We're converting our compatibility data into a machine-readable JSON format. This compatibility table still uses the old format, because we haven't yet converted the data it contains. Find out how you can help! (en-US)
Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari
Basic support (Yes) (Yes) (Yes) (Yes) (Yes)
Feature Android Chrome for Android Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile
Basic support (Yes) (Yes) (Yes) (Yes) (Yes) (Yes)