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+---
+title: Object.prototype.constructor
+slug: Web/JavaScript/Reference/Global_Objects/Object/constructor
+tags:
+  - JavaScript
+  - Object
+  - Property
+  - Prototype
+translation_of: Web/JavaScript/Reference/Global_Objects/Object/constructor
+---
+<p>{{JSRef}}</p>
+
+<p>返回创建实例对象的 {{jsxref("Object")}} 构造函数的引用。注意，此属性的值是对函数本身的引用，而不是一个包含函数名称的字符串。对原始类型来说，如<code>1</code>，<code>true</code>和<code>"test"</code>，该值只可读。</p>
+
+<h2 id="Description" name="Description">描述</h2>
+
+<p>所有对象都会从它的原型上继承一个 <code>constructor</code> 属性：</p>
+
+<pre class="brush: js">var o = {};
+o.constructor === Object; // true
+
+var o = new Object;
+o.constructor === Object; // true
+
+var a = [];
+a.constructor === Array; // true
+
+var a = new Array;
+a.constructor === Array // true
+
+var n = new Number(3);
+n.constructor === Number; // true</pre>
+
+<h2 id="Examples" name="Examples">示例</h2>
+
+<h3 id="Example_Displaying_the_constructor_of_an_object" name="Example:_Displaying_the_constructor_of_an_object">打印一个对象的构造函数</h3>
+
+<p>以下示例创建一个原型，<code>Tree</code>，以及该类型的对象，即<code>theTree</code>。 然后打印<code>theTree</code>对象的<code>constructor</code>属性。</p>
+
+<pre class="brush:js">function Tree(name) {
+   this.name = name;
+}
+
+var theTree = new Tree("Redwood");
+console.log( "theTree.constructor is " + theTree.constructor );</pre>
+
+<p>打印输出：</p>
+
+<pre class="brush:js">theTree.constructor is function Tree(name) {
+    this.name = name;
+}</pre>
+
+<h3 id="Example_Changing_the_constructor_of_an_object" name="Example:_Changing_the_constructor_of_an_object">改变对象的 constructor</h3>
+
+<p>下面的例子展示了如何修改基本类型对象的 <code>constructor</code> 属性的值。只有 <code>true</code>, <code>1</code> 和 <code>"test"</code> 的不受影响，因为创建他们的是只读的原生构造函数（native constructors）。这个例子也说明了依赖一个对象的 <code>constructor</code> 属性并不安全。</p>
+
+<pre class="brush:js">function Type() { };
+
+var	types = [
+	new Array,
+    [],
+	new Boolean,
+    true,        // remains unchanged
+	new Date,
+	new Error,
+	new Function,
+	function(){},
+	Math,
+	new Number,
+	1,           // remains unchanged
+	new Object,
+	{},
+	new RegExp,
+	/(?:)/,
+	new String,
+	"test"       // remains unchanged
+];
+
+for(var i = 0; i &lt; types.length; i++) {
+	types[i].constructor = Type;
+	types[i] = [ types[i].constructor, types[i] instanceof Type, types[i].toString() ];
+};
+
+console.log( types.join("\n") );
+</pre>
+
+<p>此示例显示以下输出：</p>
+
+<pre class="brush: js">function Type() {},false,
+function Type() {},false,
+function Type() {},false,false
+function Boolean() {
+    [native code]
+},false,true
+function Type() {},false,Mon Sep 01 2014 16:03:49 GMT+0600
+function Type() {},false,Error
+function Type() {},false,function anonymous() {
+
+}
+function Type() {},false,function () {}
+function Type() {},false,[object Math]
+function Type() {},false,0
+function Number() {
+    [native code]
+},false,1
+function Type() {},false,[object Object]
+function Type() {},false,[object Object]
+function Type() {},false,/(?:)/
+function Type() {},false,/(?:)/
+function Type() {},false,
+function String() {
+    [native code]
+},false,test
+</pre>
+
+
+
+<h3 id="改变函数的_constructor">改变函数的 constructor</h3>
+
+<p>大多数情况下，此属性用于定义一个构造函数，并使用<strong>new</strong>和继承原型链进一步调用它。</p>
+
+<pre class="brush: js">function Parent() {}
+Parent.prototype.parentMethod = function parentMethod() {};
+
+function Child() {}
+Child.prototype = Object.create(Parent.prototype); // re-define child prototype to Parent prototype
+
+Child.prototype.constructor = Child; // return original constructor to Child</pre>
+
+<p>但为什么我们需要在这里执行最后一行？很不幸正确答案是 - 看情况而定。</p>
+
+<p>让我们来尝试定义在哪些情况下，重新分配原始构造函数会发挥重要作用，以及在什么时候它就是额外的未使用的（无效的）代码行。</p>
+
+<p>试想下一种情况：该对象具有创建自身的<strong>create</strong>方法。</p>
+
+<pre class="brush: js">function Parent() {};
+function CreatedConstructor() {}
+
+CreatedConstructor.prototype = Object.create(Parent.prototype);
+
+CreatedConstructor.prototype.create = function create() {
+  return new this.constructor();
+}
+
+new CreatedConstructor().create().create(); // error undefined is not a function since constructor === Parent
+</pre>
+
+<p>在上面的示例中，将显示异常，因为构造函数链接到Parent。</p>
+
+<p>为了避免它，只需分配您将要使用的必要构造函数。</p>
+
+<pre class="brush: js">function Parent() {};
+function CreatedConstructor() {}
+
+CreatedConstructor.prototype = Object.create(Parent.prototype);
+CreatedConstructor.prototype.constructor = CreatedConstructor; // set right constructor for further using
+
+CreatedConstructor.prototype.create = function create() {
+  return new this.constructor();
+}
+
+new CreatedConstructor().create().create(); // it's pretty fine</pre>
+
+<p>好的，现在很清楚为什么更改构造函数会很有用。</p>
+
+<p>让我们再考虑一个案例。</p>
+
+<pre class="brush: js">function ParentWithStatic() {}
+
+ParentWithStatic.startPosition = { x: 0, y:0 };
+ParentWithStatic.getStartPosition = function getStartPosition() {
+  return this.startPosition;
+}
+
+function Child(x, y) {
+  this.position = {
+    x: x,
+    y: y
+  };
+}
+
+Child.prototype = Object.create(ParentWithStatic.prototype);
+Child.prototype.constructor = Child;
+
+Child.prototype.getOffsetByInitialPosition = function getOffsetByInitialPosition() {
+  var position = this.position;
+  var startPosition = this.constructor.getStartPosition(); // error undefined is not a function, since the constructor is Child
+
+  return {
+    offsetX: startPosition.x - position.x,
+    offsetY: startPosition.y - position.y
+  }
+};</pre>
+
+<p>对于此示例，我们需要保持父构造函数继续正常工作。</p>
+
+<p><strong>总结</strong>：手动设置或更新构造函数可能会导致不同且有时令人困惑的后果。为了防止它，只需在每个特定情况下定义构造函数的角色。在大多数情况下，不使用构造函数，并且不需要重新分配构造函数。</p>
+
+<h2 id="规范" style="margin-bottom: 20px; line-height: 30px;">规范</h2>
+
+<table class="standard-table">
+ <tbody>
+  <tr>
+   <th scope="col">Specification</th>
+   <th scope="col">Status</th>
+   <th scope="col">Comment</th>
+  </tr>
+  <tr>
+   <td>{{SpecName('ES1')}}</td>
+   <td>{{Spec2('ES1')}}</td>
+   <td>Initial definition. Implemented in JavaScript 1.1.</td>
+  </tr>
+  <tr>
+   <td>{{SpecName('ES5.1', '#sec-15.2.4.1', 'Object.prototype.constructor')}}</td>
+   <td>{{Spec2('ES5.1')}}</td>
+   <td></td>
+  </tr>
+  <tr>
+   <td>{{SpecName('ES6', '#sec-object.prototype.constructor', 'Object.prototype.constructor')}}</td>
+   <td>{{Spec2('ES6')}}</td>
+   <td></td>
+  </tr>
+  <tr>
+   <td>{{SpecName('ESDraft', '#sec-object.prototype.constructor', 'Object.prototype.constructor')}}</td>
+   <td>{{Spec2('ESDraft')}}</td>
+   <td></td>
+  </tr>
+ </tbody>
+</table>
+
+<h2 id="浏览器兼容">浏览器兼容</h2>
+
+<div class="hidden">The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out <a href="https://github.com/mdn/browser-compat-data">https://github.com/mdn/browser-compat-data</a> and send us a pull request.</div>
+
+<p>{{Compat("javascript.builtins.Object.constructor")}}</p>