JavaScript对象的constructor属性介绍

   <p>constructor 属性始终指向创建当前对象的构造函数。比如下面例子：</p>    <pre>  <code class="language-javascript">// 等价于 var foo = new Array(1, 56, 34, 12);    var arr = [1, 56, 34, 12];    console.log(arr.constructor === Array); // true    // 等价于 var foo = new Function();    var Foo = function() { };    console.log(Foo.constructor === Function); // true    // 由构造函数实例化一个obj对象    var obj = new Foo();    console.log(obj.constructor === Foo); // true    // 将上面两段代码合起来，就得到下面的结论    console.log(obj.constructor.constructor === Function); // true </code></pre>    <p>但是当constructor遇到prototype时，有趣的事情就发生了。</p>    <p>我们知道每个函数都有一个默认的属性prototype，而这个prototype的constructor默认指向这个函数。如下例所示：</p>    <pre>  <code class="language-javascript">function Person(name) {        this.name = name;    };    Person.prototype.getName = function() {        return this.name;    };    var p = new Person("ZhangSan");    console.log(p.constructor === Person);  // true    console.log(Person.prototype.constructor === Person); // true    // 将上两行代码合并就得到如下结果    console.log(p.constructor.prototype.constructor === Person); // true </code></pre>    <p>当时当我们重新定义函数的prototype时（注意：和上例的区别，这里不是修改而是覆盖），constructor属性的行为就有点奇怪了，如下示例：</p>    <pre>  <code class="language-javascript">function Person(name) {        this.name = name;    };    Person.prototype = {        getName: function() {            return this.name;        }    };    var p = new Person("ZhangSan");    console.log(p.constructor === Person);  // false    console.log(Person.prototype.constructor === Person); // false    console.log(p.constructor.prototype.constructor === Person); // false </code></pre>    <p>为什么呢？</p>    <p>原来是因为覆盖Person.prototype时，等价于进行如下代码操作：</p>    <pre>  <code class="language-javascript">Person.prototype = new Object({        getName: function() {            return this.name;        }    });</code></pre>    <p>而constructor属性始终指向创建自身的构造函数，所以此时Person.prototype.constructor === Object，即是：</p>    <pre>  <code class="language-javascript">function Person(name) {        this.name = name;    };    Person.prototype = {        getName: function() {            return this.name;        }    };    var p = new Person("ZhangSan");    console.log(p.constructor === Object);  // true    console.log(Person.prototype.constructor === Object); // true    console.log(p.constructor.prototype.constructor === Object); // true </code></pre>    <p>怎么修正这种问题呢？方法也很简单，重新覆盖Person.prototype.constructor即可：</p>    <pre>  <code class="language-javascript">function Person(name) {        this.name = name;    };    Person.prototype = new Object({        getName: function() {            return this.name;        }    });    Person.prototype.constructor = Person;    var p = new Person("ZhangSan");    console.log(p.constructor === Person);  // true    console.log(Person.prototype.constructor === Person); // true    console.log(p.constructor.prototype.constructor === Person); // true </code></pre>    <p> </p>    <p>来自：http://webexpressor.github.io/JavaScript/2012/09/24/the-constructor-of-javascripts-object.html</p>    <p> </p>