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Revision 640413 of Object.create()

  • 版本网址缩略名： Web/JavaScript/Reference/Global_Objects/Object/create
  • 版本标题： create
  • 版本 id： 640413
  • 创建于：
  • 创建者： AlexChao
  • 是否是当前版本？ 否
  • 评论
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修订内容

{{JSRef("Global_Objects", "Object")}}

概述

创建一个拥有指定原型和若干个指定属性的对象。

语法

Object.create(proto [, propertiesObject ])

参数

proto
一个对象，作为新创建对象的原型。
propertiesObject
一个对象值,可以包含若干个属性,属性名为新建对象的属性名,属性值为那个属性的属性描述符对象.

抛出异常

如果 proto 参数不是 null 或一个对象值，则抛出一个 {{jsxref("Global_Objects/TypeError", "TypeError")}} 异常。

例子

使用Object.create

var o;

// 创建一个原型为null的空对象
o = Object.create(null);


o = {};
// 以字面量方式创建的空对象就相当于:
o = Object.create(Object.prototype);


o = Object.create(Object.prototype, {
  // foo会成为所创建对象的数据属性
  foo: { writable:true, configurable:true, value: "hello" },
  // bar会成为所创建对象的访问器属性
  bar: {
    configurable: false,
    get: function() { return 10 },
    set: function(value) { console.log("Setting `o.bar` to", value) }
}})


function Constructor(){}
o = new Constructor();
// 上面的一句就相当于:
o = Object.create(Constructor.prototype);
// 当然,如果在Constructor函数中有一些初始化代码,Object.create不能执行那些代码


// 创建一个以另一个空对象为原型,且拥有一个属性p的对象
o = Object.create({}, { p: { value: 42 } })

// 省略了的属性特性默认为false,所以属性p是不可写,不可枚举,不可配置的:
o.p = 24
o.p
//42

o.q = 12
for (var prop in o) {
   console.log(prop)
}
//"q"

delete o.p
//false

//创建一个可写的,可枚举的,可配置的属性p
o2 = Object.create({}, { p: { value: 42, writable: true, enumerable: true, configurable: true } });

使用Object.create实现原型继承

下面的例子演示了如何使用Object.create来实现单继承.

//Shape - superclass
function Shape() {
  this.x = 0;
  this.y = 0;
}

Shape.prototype.move = function(x, y) {
    this.x += x;
    this.y += y;
    console.info("Shape moved.");
};

// Rectangle - subclass
function Rectangle() {
  Shape.call(this); //call super constructor.
}

Rectangle.prototype = Object.create(Shape.prototype);

var rect = new Rectangle();

rect instanceof Rectangle //true.
rect instanceof Shape //true.

rect.move(); //Outputs, "Shape moved."

如果你希望能继承到多个对象,则可以使用混入的方式.

function MyClass() {
     SuperClass.call(this);
     OtherSuperClass.call(this);
}

MyClass.prototype = Object.create(SuperClass.prototype); //inherit
mixin(MyClass.prototype, OtherSuperClass.prototype); //mixin

MyClass.prototype.myMethod = function() {
     // do a thing
};

mixin函数会把超类原型上的函数拷贝到子类原型上,这里mixin函数没有给出,需要由你实现.

Polyfill

这个polyfill只实现了创建一个指定原型的对象的功能，而不能同时添加特定的属性，也就是没有实现原生的Object.create函数中的第二个参数。

if (typeof Object.create != 'function') {
    (function () {
        var F = function () {};
        Object.create = function (o) {
            if (arguments.length > 1) { 
              throw Error('Second argument not supported');
            }
            if (o === null) { 
              throw Error('Cannot set a null [[Prototype]]');
            }
            if (typeof o != 'object') { 
              throw TypeError('Argument must be an object');
            }
            F.prototype = o;
            return new F();
        };
    })();
}

规范

规范版本 规范状态 注解
{{SpecName('ES5.1', '#sec-15.2.3.5', 'Object.create')}} {{Spec2('ES5.1')}} Initial definition. Implemented in JavaScript 1.8.5
{{SpecName('ES6', '#sec-object.create', 'Object.create')}} {{Spec2('ES6')}}  

浏览器兼容性

{{ CompatibilityTable() }}

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari
Basic support 5 {{ CompatGeckoDesktop("2") }} 9 11.60 5
Feature Firefox Mobile (Gecko) Android IE Mobile Opera Mobile Safari Mobile
Basic support {{ CompatGeckoDesktop("2") }} {{ CompatVersionUnknown() }} {{ CompatUnknown() }} 11.50 {{ CompatVersionUnknown() }}

相关链接

  • {{jsxref("Object.defineProperty")}}
  • {{jsxref("Object.defineProperties")}}
  • {{jsxref("Object.prototype.isPrototypeOf")}}
  • John Resig's post on getPrototypeOf

修订版来源

 
<p name="Summary">{{JSRef("Global_Objects", "Object")}}</p>
<h2 id="Summary" name="Summary">概述</h2>
<p>创建一个拥有指定原型和若干个指定属性的对象。</p>
<h2 id="Syntax" name="Syntax">语法</h2>
<pre class="syntaxbox">
<code>Object.create(<em>proto</em> [, <em>propertiesObject</em> ])</code></pre>
<h2 id="Parameters" name="Parameters">参数</h2>
<dl>
 <dt>
  proto</dt>
 <dd>
  一个对象，作为新创建对象的原型。</dd>
 <dt>
  propertiesObject</dt>
 <dd>
  一个对象值,可以包含若干个属性,属性名为新建对象的属性名,属性值为那个属性的属性描述符对象.</dd>
</dl>
<h3 id="Description" name="Description">抛出异常</h3>
<p>如果 proto 参数不是 <code>null </code>或一个对象值，则抛出一个 {{jsxref("Global_Objects/TypeError", "TypeError")}} 异常。</p>
<h2 id="Examples" name="Examples">例子</h2>
<h4 id=".E4.BD.BF.E7.94.A8Object.create">使用Object.create</h4>
<pre class="brush: js">
var o;

// 创建一个原型为null的空对象
o = Object.create(null);


o = {};
// 以字面量方式创建的空对象就相当于:
o = Object.create(Object.prototype);


o = Object.create(Object.prototype, {
  // foo会成为所创建对象的数据属性
  foo: { writable:true, configurable:true, value: "hello" },
  // bar会成为所创建对象的访问器属性
  bar: {
    configurable: false,
    get: function() { return 10 },
    set: function(value) { console.log("Setting `o.bar` to", value) }
}})


function Constructor(){}
o = new Constructor();
// 上面的一句就相当于:
o = Object.create(Constructor.prototype);
// 当然,如果在Constructor函数中有一些初始化代码,Object.create不能执行那些代码


// 创建一个以另一个空对象为原型,且拥有一个属性p的对象
o = Object.create({}, { p: { value: 42 } })

// 省略了的属性特性默认为false,所以属性p是不可写,不可枚举,不可配置的:
o.p = 24
o.p
//42

o.q = 12
for (var prop in o) {
   console.log(prop)
}
//"q"

delete o.p
//false

//创建一个可写的,可枚举的,可配置的属性p
o2 = Object.create({}, { p: { value: 42, writable: true, enumerable: true, configurable: true } });
</pre>
<h4 id=".E4.BD.BF.E7.94.A8Object.create.E5.AE.9E.E7.8E.B0.E5.8E.9F.E5.9E.8B.E7.BB.A7.E6.89.BF">使用Object.create实现原型继承</h4>
<p>下面的例子演示了如何使用Object.create来实现单继承.</p>
<div class="highlight">
 <pre class="brush: js">
//Shape - superclass
function Shape() {
  this.x = 0;
  this.y = 0;
}

Shape.prototype.move = function(x, y) {
    this.x += x;
    this.y += y;
    console.info("Shape moved.");
};

// Rectangle - subclass
function Rectangle() {
  Shape.call(this); //call super constructor.
}

Rectangle.prototype = Object.create(Shape.prototype);

var rect = new Rectangle();

rect instanceof Rectangle //true.
rect instanceof Shape //true.

rect.move(); //Outputs, "Shape moved."
</pre>
</div>
<p>如果你希望能继承到多个对象,则可以使用<span class="short_text" id="result_box" lang="zh-CN"><span>混入的方式</span></span>.</p>
<div class="highlight">
 <pre class="brush: js">
function MyClass() {
     SuperClass.call(this);
     OtherSuperClass.call(this);
}

MyClass.prototype = Object.create(SuperClass.prototype); //inherit
mixin(MyClass.prototype, OtherSuperClass.prototype); //mixin

MyClass.prototype.myMethod = function() {
     // do a thing
};
</pre>
</div>
<p>mixin函数会把超类原型上的函数拷贝到子类原型上,这里mixin函数没有给出,需要由你实现.</p>
<h3 id="Polyfill" style="line-height: 24px;">Polyfill</h3>
<p>这个polyfill只实现了创建一个指定原型的对象的功能，而不能同时添加特定的属性，也就是没有实现原生的Object.create函数中的第二个参数。</p>
<pre class="brush: js  language-js" data-number="" style="padding: 1em 0px 1em 30px; border-left-width: 6px; border-left-style: solid; border-left-color: rgba(0, 83, 159, 0.65098); font-family: Consolas, Monaco, 'Andale Mono', monospace; font-size: 14px; direction: ltr; white-space: normal; word-break: normal; tab-size: 4; text-shadow: none; background-image: url(https://developer.cdn.mozilla.net/media/redesign/img/blueprint-dark.png); background-color: rgba(234, 239, 242, 0.247059); background-position: 50% 0%;">
<code class="language-js" style="font-family: Consolas, Monaco, 'Andale Mono', monospace; direction: ltr; white-space: pre; word-spacing: normal; word-break: normal; tab-size: 4; color: inherit; text-shadow: none;"><span class="token keyword" style="color: rgb(0, 119, 170);">if</span> <span class="token punctuation" style="color: rgb(153, 153, 153);">(</span><span class="token keyword" style="color: rgb(0, 119, 170);">typeof</span> Object<span class="token punctuation" style="color: rgb(153, 153, 153);">.</span>create <span class="token operator" style="color: rgb(166, 127, 89); background: rgba(255, 255, 255, 0.498039);">!</span><span class="token operator" style="color: rgb(166, 127, 89); background: rgba(255, 255, 255, 0.498039);">=</span> <span class="token string" style="color: rgb(102, 153, 0);">'function'</span><span class="token punctuation" style="color: rgb(153, 153, 153);">)</span> <span class="token punctuation" style="color: rgb(153, 153, 153);">{</span>
    <span class="token punctuation" style="color: rgb(153, 153, 153);">(</span><span class="token keyword" style="color: rgb(0, 119, 170);">function</span> <span class="token punctuation" style="color: rgb(153, 153, 153);">(</span><span class="token punctuation" style="color: rgb(153, 153, 153);">)</span> <span class="token punctuation" style="color: rgb(153, 153, 153);">{</span>
        <span class="token keyword" style="color: rgb(0, 119, 170);">var</span> F <span class="token operator" style="color: rgb(166, 127, 89); background: rgba(255, 255, 255, 0.498039);">=</span> <span class="token keyword" style="color: rgb(0, 119, 170);">function</span> <span class="token punctuation" style="color: rgb(153, 153, 153);">(</span><span class="token punctuation" style="color: rgb(153, 153, 153);">)</span> <span class="token punctuation" style="color: rgb(153, 153, 153);">{</span><span class="token punctuation" style="color: rgb(153, 153, 153);">}</span><span class="token punctuation" style="color: rgb(153, 153, 153);">;</span>
        Object<span class="token punctuation" style="color: rgb(153, 153, 153);">.</span>create <span class="token operator" style="color: rgb(166, 127, 89); background: rgba(255, 255, 255, 0.498039);">=</span> <span class="token keyword" style="color: rgb(0, 119, 170);">function</span> <span class="token punctuation" style="color: rgb(153, 153, 153);">(</span>o<span class="token punctuation" style="color: rgb(153, 153, 153);">)</span> <span class="token punctuation" style="color: rgb(153, 153, 153);">{</span>
            <span class="token keyword" style="color: rgb(0, 119, 170);">if</span> <span class="token punctuation" style="color: rgb(153, 153, 153);">(</span>arguments<span class="token punctuation" style="color: rgb(153, 153, 153);">.</span>length &gt; <span class="token number" style="color: rgb(153, 0, 85);">1</span><span class="token punctuation" style="color: rgb(153, 153, 153);">)</span> <span class="token punctuation" style="color: rgb(153, 153, 153);">{</span> 
              throw <span class="token function">Error<span class="token punctuation" style="color: rgb(153, 153, 153);">(</span></span><span class="token string" style="color: rgb(102, 153, 0);">'Second argument not supported'</span><span class="token punctuation" style="color: rgb(153, 153, 153);">)</span><span class="token punctuation" style="color: rgb(153, 153, 153);">;</span>
            <span class="token punctuation" style="color: rgb(153, 153, 153);">}</span>
            <span class="token keyword" style="color: rgb(0, 119, 170);">if</span> <span class="token punctuation" style="color: rgb(153, 153, 153);">(</span>o <span class="token operator" style="color: rgb(166, 127, 89); background: rgba(255, 255, 255, 0.498039);">==</span><span class="token operator" style="color: rgb(166, 127, 89); background: rgba(255, 255, 255, 0.498039);">=</span> <span class="token keyword" style="color: rgb(0, 119, 170);">null</span><span class="token punctuation" style="color: rgb(153, 153, 153);">)</span> <span class="token punctuation" style="color: rgb(153, 153, 153);">{</span> 
              throw <span class="token function">Error<span class="token punctuation" style="color: rgb(153, 153, 153);">(</span></span><span class="token string" style="color: rgb(102, 153, 0);">'Cannot set a null [[Prototype]]'</span><span class="token punctuation" style="color: rgb(153, 153, 153);">)</span><span class="token punctuation" style="color: rgb(153, 153, 153);">;</span>
            <span class="token punctuation" style="color: rgb(153, 153, 153);">}</span>
            <span class="token keyword" style="color: rgb(0, 119, 170);">if</span> <span class="token punctuation" style="color: rgb(153, 153, 153);">(</span><span class="token keyword" style="color: rgb(0, 119, 170);">typeof</span> o <span class="token operator" style="color: rgb(166, 127, 89); background: rgba(255, 255, 255, 0.498039);">!</span><span class="token operator" style="color: rgb(166, 127, 89); background: rgba(255, 255, 255, 0.498039);">=</span> <span class="token string" style="color: rgb(102, 153, 0);">'object'</span><span class="token punctuation" style="color: rgb(153, 153, 153);">)</span> <span class="token punctuation" style="color: rgb(153, 153, 153);">{</span> 
              throw <span class="token function">TypeError<span class="token punctuation" style="color: rgb(153, 153, 153);">(</span></span><span class="token string" style="color: rgb(102, 153, 0);">'Argument must be an object'</span><span class="token punctuation" style="color: rgb(153, 153, 153);">)</span><span class="token punctuation" style="color: rgb(153, 153, 153);">;</span>
            <span class="token punctuation" style="color: rgb(153, 153, 153);">}</span>
            F<span class="token punctuation" style="color: rgb(153, 153, 153);">.</span>prototype <span class="token operator" style="color: rgb(166, 127, 89); background: rgba(255, 255, 255, 0.498039);">=</span> o<span class="token punctuation" style="color: rgb(153, 153, 153);">;</span>
            <span class="token keyword" style="color: rgb(0, 119, 170);">return</span> <span class="token keyword" style="color: rgb(0, 119, 170);">new</span> <span class="token class-name">F</span><span class="token punctuation" style="color: rgb(153, 153, 153);">(</span><span class="token punctuation" style="color: rgb(153, 153, 153);">)</span><span class="token punctuation" style="color: rgb(153, 153, 153);">;</span>
        <span class="token punctuation" style="color: rgb(153, 153, 153);">}</span><span class="token punctuation" style="color: rgb(153, 153, 153);">;</span>
    <span class="token punctuation" style="color: rgb(153, 153, 153);">}</span><span class="token punctuation" style="color: rgb(153, 153, 153);">)</span><span class="token punctuation" style="color: rgb(153, 153, 153);">(</span><span class="token punctuation" style="color: rgb(153, 153, 153);">)</span><span class="token punctuation" style="color: rgb(153, 153, 153);">;</span>
<span class="token punctuation" style="color: rgb(153, 153, 153);">}</span></code></pre>
<h2 id="Specifications" style="margin-bottom: 20px; line-height: 30px;">规范</h2>
<table class="standard-table">
 <tbody>
  <tr>
   <th scope="col">规范版本</th>
   <th scope="col">规范状态</th>
   <th scope="col">注解</th>
  </tr>
  <tr>
   <td>{{SpecName('ES5.1', '#sec-15.2.3.5', 'Object.create')}}</td>
   <td>{{Spec2('ES5.1')}}</td>
   <td>Initial definition. Implemented in JavaScript 1.8.5</td>
  </tr>
  <tr>
   <td>{{SpecName('ES6', '#sec-object.create', 'Object.create')}}</td>
   <td>{{Spec2('ES6')}}</td>
   <td>&nbsp;</td>
  </tr>
 </tbody>
</table>
<h2 id=".E6.B5.8F.E8.A7.88.E5.99.A8.E5.85.BC.E5.AE.B9.E6.80.A7">浏览器兼容性</h2>
<p>{{ CompatibilityTable() }}</p>
<div id="compat-desktop">
 <table class="compat-table">
  <tbody>
   <tr>
    <th>Feature</th>
    <th>Chrome</th>
    <th>Firefox (Gecko)</th>
    <th>Internet Explorer</th>
    <th>Opera</th>
    <th>Safari</th>
   </tr>
   <tr>
    <td>Basic support</td>
    <td>5</td>
    <td>{{ CompatGeckoDesktop("2") }}</td>
    <td>9</td>
    <td>11.60</td>
    <td>5</td>
   </tr>
  </tbody>
 </table>
</div>
<div id="compat-mobile">
 <table class="compat-table">
  <tbody>
   <tr>
    <th>Feature</th>
    <th>Firefox Mobile (Gecko)</th>
    <th>Android</th>
    <th>IE Mobile</th>
    <th>Opera Mobile</th>
    <th>Safari Mobile</th>
   </tr>
   <tr>
    <td>Basic support</td>
    <td>{{ CompatGeckoDesktop("2") }}</td>
    <td>{{ CompatVersionUnknown() }}</td>
    <td>{{ CompatUnknown() }}</td>
    <td>11.50</td>
    <td>{{ CompatVersionUnknown() }}</td>
   </tr>
  </tbody>
 </table>
</div>
<h2 id="See_also" name="See_also" style="margin-bottom: 20px; line-height: 30px;">相关链接</h2>
<ul>
 <li>{{jsxref("Object.defineProperty")}}</li>
 <li>{{jsxref("Object.defineProperties")}}</li>
 <li>{{jsxref("Object.prototype.isPrototypeOf")}}</li>
 <li>John Resig's post on&nbsp;<a class="external external-icon" href="https://ejohn.org/blog/objectgetprototypeof/" style="white-space: pre-line;" title="https://ejohn.org/blog/objectgetprototypeof/">getPrototypeOf</a></li>
</ul>
恢复到这个版本