Object | JavaScript

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描述
构造函数
静态方法
实例特性
实例方法
范例
规范
浏览器兼容性
另请参阅
相关话题

Object class represents one of JavaScript 的数据类型 . It is used to store various keyed collections and more complex entities. Objects can be created using the Object() constructor or the 对象初始化器/文字句法 .

描述

Nearly all objects in JavaScript are instances of Object ; a typical object inherits properties (including methods) from Object.prototype , although these properties may be shadowed (a.k.a. overridden). However, an Object may be deliberately created for which this is not true (e.g. by Object.create(null) ), or it may be altered so that this is no longer true (e.g. with Object.setPrototypeOf ).

Changes to the Object prototype object are seen by all objects through prototype chaining, unless the properties and methods subject to those changes are overridden further along the prototype chain. This provides a very powerful although potentially dangerous mechanism to override or extend object behavior.

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() .

另请参阅对象初始化器/文字句法 .

从对象删除特性

There isn't any method in an Object itself to delete its own properties (such as Map.prototype.delete() ). To do so, one must use the delete operator .

构造函数

Object(): 创建新的 Object object. It is a wrapper for the given value.

静态方法

Object.assign()
Object.create()
Object.defineProperty()
Object.defineProperties()
Object.entries(): Returns an array containing all of the [key, value] pairs of a given object's own enumerable string properties.
Object.freeze()
Object.fromEntries(): Returns a new object from an iterable of [key, value] pairs. (This is the reverse of Object.entries ).
Object.getOwnPropertyDescriptor()
Object.getOwnPropertyDescriptors()
Object.getOwnPropertyNames(): Returns an array containing the names of all of the given object's own enumerable and non-enumerable properties.
Object.getOwnPropertySymbols()
Object.getPrototypeOf(): Returns the prototype (internal [[Prototype]] property) 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()
Object.isFrozen()
Object.isSealed()
Object.keys(): Returns an array containing the names of all of the given object's own enumerable string properties.
Object.preventExtensions()
Object.seal()
Object.setPrototypeOf(): Sets the object's prototype (its internal [[Prototype]] property).
Object.values(): Returns an array containing the values that correspond to all of a given object's own enumerable string properties.

实例特性

Object.prototype.constructor
Object.prototype.__proto__
Object.prototype.__noSuchMethod__

实例方法

Object.prototype.__defineGetter__()
Object.prototype.__defineSetter__()
Object.prototype.__lookupGetter__(): Returns the function associated with the specified property by the __defineGetter__() 方法。
Object.prototype.__lookupSetter__(): Returns the function associated with the specified property by the __defineSetter__() 方法。
Object.prototype.hasOwnProperty()
Object.prototype.isPrototypeOf()
Object.prototype.propertyIsEnumerable(): Returns a boolean indicating if the internal ECMAScript [[Enumerable]] attribute 有设置。
Object.prototype.toLocaleString(): 调用 toString() .
Object.prototype.toString()
Object.prototype.unwatch()
Object.prototype.valueOf()
Object.prototype.watch()

范例

使用 `Object` given `undefined` and `null` types

The following examples store an empty Object object in o :

let o = new Object()

let o = new Object(undefined)

let o = new Object(null)

使用 `Object` to create `布尔` 对象

The following examples store 布尔 objects in o :

// equivalent to o = new Boolean(true)
let o = new Object(true)

// equivalent to o = new Boolean(false)
let o = new Object(Boolean())

对象原型

When altering the behavior of existing Object.prototype methods, consider injecting code by wrapping your extension before or after the existing logic. For example, this (untested) code will pre-conditionally execute custom logic before the built-in logic or someone else's extension is executed.

When a function is called, the arguments to the call are held in the array-like "variable" arguments . For example, in the call myFn(a, b, c) , the arguments within myFn 's body will contain 3 array-like elements corresponding to (a, b, c) .

When modifying prototypes with hooks, pass this and the arguments (the call state) to the current behavior by calling apply() on the function. This pattern can be used for any prototype, such as Node.prototype , Function.prototype ，等。

var current = Object.prototype.valueOf;
// Since my property "-prop-value" is cross-cutting and isn't always
// on the same prototype chain, I want to modify Object.prototype:
Object.prototype.valueOf = function() {
  if (this.hasOwnProperty('-prop-value')) {
    return this['-prop-value'];
  } else {
    // It doesn't look like one of my objects, so let's fall back on
    // the default behavior by reproducing the current behavior as best we can.
    // The apply behaves like "super" in some other languages.
    // Even though valueOf() doesn't take arguments, some other hook may.
    return current.apply(this, arguments);
  }
}

Since JavaScript doesn't exactly have sub-class objects, prototype is a useful workaround to make a “base class” object of certain functions that act as objects. For example:

var Person = function(name) {
  this.name = name;
  this.canTalk = true;
};
Person.prototype.greet = function() {
  if (this.canTalk) {
    console.log('Hi, I am ' + this.name);
  }
};
var Employee = function(name, title) {
  Person.call(this, name);
  this.title = title;
};
Employee.prototype = Object.create(Person.prototype);
Employee.prototype.constructor = Employee; //If you don't set Object.prototype.constructor to Employee,
                                           //it will take prototype.constructor of Person (parent).
                                           //To avoid that, we set the prototype.constructor to Employee (child).
Employee.prototype.greet = function() {
  if (this.canTalk) {
    console.log('Hi, I am ' + this.name + ', the ' + this.title);
  }
};
var Customer = function(name) {
  Person.call(this, name);
};
Customer.prototype = Object.create(Person.prototype);
Customer.prototype.constructor = Customer; //If you don't set Object.prototype.constructor to Customer,
                                           //it will take prototype.constructor of Person (parent).
                                           //To avoid that, we set the prototype.constructor to Customer (child).
var Mime = function(name) {
  Person.call(this, name);
  this.canTalk = false;
};
Mime.prototype = Object.create(Person.prototype);
Mime.prototype.constructor = Mime; //If you don't set Object.prototype.constructor to Mime,
                                   //it will take prototype.constructor of Person (parent).
                                   //To avoid that, we set the prototype.constructor to Mime (child).
var bob = new Employee('Bob', 'Builder');
var joe = new Customer('Joe');
var rg = new Employee('Red Green', 'Handyman');
var mike = new Customer('Mike');
var mime = new Mime('Mime');
bob.greet();
// Hi, I am Bob, the Builder
joe.greet();
// Hi, I am Joe
rg.greet();
// Hi, I am Red Green, the Handyman
mike.greet();
// Hi, I am Mike
mime.greet();

规范

规范
ECMAScript (ECMA-262) 在该规范中的 Object 定义。

浏览器兼容性

The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request. 更新 GitHub 上的兼容性数据

	Desktop						Mobile						Server
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet	Node.js
`Object`	Chrome 1	Edge 12	Firefox 1	IE 3	Opera 3	Safari 1	WebView Android 1	Chrome Android 18	Firefox Android 4	Opera Android 10.1	Safari iOS 1	Samsung Internet Android 1.0	nodejs Yes
`Object()` 构造函数	Chrome 1	Edge 12	Firefox 1	IE 3	Opera 3	Safari 1	WebView Android 1	Chrome Android 18	Firefox Android 4	Opera Android 10.1	Safari iOS 1	Samsung Internet Android 1.0	nodejs Yes
`assign`	Chrome 45	Edge 12	Firefox 34	IE No	Opera 32	Safari 9	WebView Android 45	Chrome Android 45	Firefox Android 34	Opera Android 32	Safari iOS 9	Samsung Internet Android 5.0	nodejs 4.0.0
`构造函数`	Chrome 1	Edge 12	Firefox 1	IE 4	Opera 4	Safari 1	WebView Android 1	Chrome Android 18	Firefox Android 4	Opera Android 10.1	Safari iOS 1	Samsung Internet Android 1.0	nodejs Yes
`create`	Chrome 5	Edge 12	Firefox 4	IE 9	Opera 11.6	Safari 5	WebView Android 1	Chrome Android 18	Firefox Android 4	Opera Android 12	Safari iOS 5	Samsung Internet Android 1.0	nodejs Yes
`__defineGetter__` 弃用	Chrome 1	Edge 12	Firefox 1 1 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.	IE 11	Opera 9.5	Safari 3	WebView Android 1	Chrome Android 18	Firefox Android 4	Opera Android 10.1	Safari iOS 1	Samsung Internet Android 1.0	nodejs Yes
`defineProperties`	Chrome 5	Edge 12	Firefox 4	IE 9	Opera 11.6	Safari 5	WebView Android 1	Chrome Android 18	Firefox Android 4	Opera Android 12	Safari iOS 5	Samsung Internet Android 1.0	nodejs Yes
`defineProperty`	Chrome 5	Edge 12	Firefox 4	IE 9 9 部分支持 8 In Internet Explorer 8, this was only supported on DOM objects and with some non-standard behaviors. This was later fixed in Internet Explorer 9.	Opera 11.6	Safari 5.1 5.1 Also supported in Safari 5, but not on DOM objects.	WebView Android 1	Chrome Android 18	Firefox Android 4	Opera Android 12	Safari iOS 6 6 Also supported in Safari for iOS 4.2, but not on DOM objects.	Samsung Internet Android 1.0	nodejs Yes
`__defineSetter__` 弃用	Chrome 1	Edge 12	Firefox 1 1 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.	IE 11	Opera 9.5	Safari 3	WebView Android 1	Chrome Android 18	Firefox Android 4	Opera Android 10.1	Safari iOS 1	Samsung Internet Android 1.0	nodejs Yes
`entries`	Chrome 54	Edge 14	Firefox 47	IE No	Opera 41	Safari 10.1	WebView Android 54	Chrome Android 54	Firefox Android 47	Opera Android 41	Safari iOS 10.3	Samsung Internet Android 6.0	nodejs 7.0.0 7.0.0 6.5.0 Disabled Disabled From version 6.5.0: this feature is behind the `--harmony` runtime flag.
`freeze`	Chrome 6	Edge 12	Firefox 4	IE 9	Opera 12	Safari 5.1	WebView Android 1	Chrome Android 18	Firefox Android 4	Opera Android 12	Safari iOS 6	Samsung Internet Android 1.0	nodejs Yes
`fromEntries`	Chrome 73	Edge 79	Firefox 63	IE No	Opera 60	Safari 12.1	WebView Android 73	Chrome Android 73	Firefox Android 63	Opera Android No	Safari iOS 12.2	Samsung Internet Android No	nodejs 12.0.0
`getOwnPropertyDescriptor`	Chrome 5	Edge 12	Firefox 4	IE 9 9 部分支持 8 In Internet Explorer 8, this was only supported on DOM objects and with some non-standard behaviors. This was later fixed in Internet Explorer 9.	Opera 12	Safari 5	WebView Android 1	Chrome Android 18	Firefox Android 4	Opera Android 12	Safari iOS 5	Samsung Internet Android 1.0	nodejs Yes
`getOwnPropertyDescriptors`	Chrome 54	Edge 15	Firefox 50	IE No	Opera 41	Safari 10	WebView Android 54	Chrome Android 54	Firefox Android 50	Opera Android 41	Safari iOS 10	Samsung Internet Android 6.0	nodejs 7.0.0 7.0.0 6.5.0 Disabled Disabled From version 6.5.0: this feature is behind the `--harmony` runtime flag.
`getOwnPropertyNames`	Chrome 5	Edge 12	Firefox 4	IE 9	Opera 12	Safari 5	WebView Android 1	Chrome Android 18	Firefox Android 4	Opera Android 12	Safari iOS 5	Samsung Internet Android 1.0	nodejs Yes
`getOwnPropertySymbols`	Chrome 38	Edge 12	Firefox 36	IE No	Opera 25	Safari 9	WebView Android 38	Chrome Android 38	Firefox Android 36	Opera Android 25	Safari iOS 9	Samsung Internet Android 3.0	nodejs 0.12
`getPrototypeOf`	Chrome 5	Edge 12	Firefox 3.5	IE 9	Opera 12.1	Safari 5	WebView Android 1	Chrome Android 18	Firefox Android 4	Opera Android 12.1	Safari iOS 5	Samsung Internet Android 1.0	nodejs Yes
`hasOwnProperty`	Chrome 1	Edge 12	Firefox 1	IE 5.5	Opera 5	Safari 3	WebView Android 1	Chrome Android 18	Firefox Android 4	Opera Android 10.1	Safari iOS 1	Samsung Internet Android 1.0	nodejs Yes
`is`	Chrome 30	Edge 12	Firefox 22	IE No	Opera 17	Safari 9	WebView Android ≤37	Chrome Android 30	Firefox Android 22	Opera Android 18	Safari iOS 9	Samsung Internet Android 2.0	nodejs 0.10
`isExtensible`	Chrome 6	Edge 12	Firefox 4	IE 9	Opera 12	Safari 5.1	WebView Android 1	Chrome Android 18	Firefox Android 4	Opera Android 12	Safari iOS 6	Samsung Internet Android 1.0	nodejs Yes
`isFrozen`	Chrome 6	Edge 12	Firefox 4	IE 9	Opera 12	Safari 5.1	WebView Android 1	Chrome Android 18	Firefox Android 4	Opera Android 12	Safari iOS 6	Samsung Internet Android 1.0	nodejs Yes
`isPrototypeOf`	Chrome 1	Edge 12	Firefox 1	IE 9	Opera 4	Safari 3	WebView Android 1	Chrome Android 18	Firefox Android 4	Opera Android 10.1	Safari iOS 1	Samsung Internet Android 1.0	nodejs Yes
`isSealed`	Chrome 6	Edge 12	Firefox 4	IE 9	Opera 12	Safari 5.1	WebView Android 1	Chrome Android 18	Firefox Android 4	Opera Android 12	Safari iOS 6	Samsung Internet Android 1.0	nodejs Yes
`keys`	Chrome 5	Edge 12	Firefox 4	IE 9	Opera 12	Safari 5	WebView Android 1	Chrome Android 18	Firefox Android 4	Opera Android 12	Safari iOS 5	Samsung Internet Android 1.0	nodejs Yes
`__lookupGetter__` 弃用	Chrome 1	Edge 12	Firefox 1	IE 11	Opera 9.5	Safari 3	WebView Android 1	Chrome Android 18	Firefox Android 4	Opera Android 10.1	Safari iOS 1	Samsung Internet Android 1.0	nodejs Yes
`__lookupSetter__` 弃用	Chrome 1	Edge 12	Firefox 1	IE 11	Opera 9.5	Safari 3	WebView Android 1	Chrome Android 18	Firefox Android 4	Opera Android 10.1	Safari iOS 1	Samsung Internet Android 1.0	nodejs Yes
`preventExtensions`	Chrome 6	Edge 12	Firefox 4	IE 9	Opera 12	Safari 5.1	WebView Android 1	Chrome Android 18	Firefox Android 4	Opera Android 12	Safari iOS 6	Samsung Internet Android 1.0	nodejs Yes
`propertyIsEnumerable`	Chrome 1	Edge 12	Firefox 1	IE 5.5	Opera 4	Safari 3	WebView Android 1	Chrome Android 18	Firefox Android 4	Opera Android 10.1	Safari iOS 1	Samsung Internet Android 1.0	nodejs Yes
`__proto__` 弃用	Chrome 1	Edge 12	Firefox 1	IE 11	Opera 10.5	Safari 3	WebView Android 1	Chrome Android 18	Firefox Android 4	Opera Android 11	Safari iOS 1	Samsung Internet Android 1.0	nodejs Yes
`seal`	Chrome 6	Edge 12	Firefox 4	IE 9	Opera 12	Safari 5.1	WebView Android 1	Chrome Android 18	Firefox Android 4	Opera Android 12	Safari iOS 6	Samsung Internet Android 1.0	nodejs Yes
`setPrototypeOf`	Chrome 34	Edge 12	Firefox 31	IE 11	Opera 21	Safari 9	WebView Android 37	Chrome Android 34	Firefox Android 31	Opera Android 21	Safari iOS 9	Samsung Internet Android 2.0	nodejs 0.12
`toLocaleString`	Chrome 1	Edge 12	Firefox 1	IE 5.5	Opera 4	Safari 1	WebView Android 1	Chrome Android 18	Firefox Android 4	Opera Android 10.1	Safari iOS 1	Samsung Internet Android 1.0	nodejs Yes
`toSource` 弃用非标	Chrome No	Edge No	Firefox 1 — 74 1 — 74 Starting in Firefox 74, `toSource()` is no longer available for use by web content. It is still allowed for internal and privileged code.	IE No	Opera No	Safari No	WebView Android No	Chrome Android No	Firefox Android 4	Opera Android No	Safari iOS No	Samsung Internet Android No	nodejs No
`toString()`	Chrome 1	Edge 12	Firefox 1	IE 3	Opera 3	Safari 1	WebView Android 1	Chrome Android 18	Firefox Android 4	Opera Android 10.1	Safari iOS 1	Samsung Internet Android 1.0	nodejs Yes
`valueOf`	Chrome 1	Edge 12	Firefox 1	IE 4	Opera 3	Safari 1	WebView Android 1	Chrome Android 18	Firefox Android 4	Opera Android 10.1	Safari iOS 1	Samsung Internet Android 1.0	nodejs Yes
`值`	Chrome 54	Edge 14	Firefox 47	IE No	Opera 41	Safari 10.1	WebView Android 54	Chrome Android 54	Firefox Android 47	Opera Android 41	Safari iOS 10.3	Samsung Internet Android 6.0	nodejs 7.0.0 7.0.0 6.5.0 Disabled Disabled From version 6.5.0: this feature is behind the `--harmony` runtime flag.

图例

完整支持
不支持

弃用。不要用于新网站。

用户必须明确启用此特征。

另请参阅

对象初始化器

元数据

最后修改： May 20, 2020

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描述