js是门灵活的语言，实现一种功能往往有多种做法,ECMAScript没有明确的继承机制，而是通过模仿实现的，根据js语言的本身的特性,js实现继承有以下通用的几种方式
1.使用对象冒充实现继承(该种实现方式可以实现多继承)
实现原理:让父类的构造函数成为子类的方法,然后调用该子类的方法,通过this关键字给所有的属性和方法赋值
<script> function Parent(firstname){ this.fname = firstname; this.age = 40; this.sayAge = function(){ console.log(this.age); } } function Child(firstname){ this.parent = Parent;//把Parent函数作为成员方法 this.parent(firstname);//执行成员方法 // 相当于下面 // this.fname = firstname; // this.age = 40; // this.sayAge = function(){ // console.log(this.age); // } delete this.Parent;//删除Parent,这样构造出的对象就没有Parent了 this.saySomeThing = function(){ console.log(this.fname); this.sayAge(); } } var mychild = new Child(‘李‘); mychild.saySomeThing(); </script>
2.采用call方法改变函数上下文实现继承(该种方式不能继承原型链,若想继承原型链，则采用5混合模式)
实现原理:改变函数内部的函数上下文this,使它指向传入函数的具体对象
<script> function Parent(firstname){ this.fname = firstname; this.age = 40; this.sayAge = function(){ console.log(this.age); } } function Child(firstname){ this.saySomeThing = function(){ console.log(this.fname); this.sayAge(); } this.getName = function(){ return firstname; } } var child = new Child(‘张‘); Parent.call(child,child.getName()); child.saySomeThing(); </script>
3.采用Apply方法改变函数上下文实现继承(该种方式不能继承原型链,若想继承原型链，则采用5混合模式)
实现原理:改变函数内部的函数上下文this,使它指向传入函数的具体对象
<script> function Parent(firstname){ this.fname = firstname; this.age = 40; this.sayAge = function(){ console.log(this.age); } } function Child(firstname){ this.saySomeThing = function(){ console.log(this.fname); this.sayAge(); } this.getName = function(){ return firstname; } } var child = new Child(‘张‘); Parent.apply(child,[child.getName()]); child.saySomeThing(); </script>
4.采用原型链的方式实现继承
实现原理:使子类原型对象指向父类的实例以实现继承,即重写类的原型,弊端是不能直接实现多继承
<script> function Parent(){ this.sayAge = function(){ console.log(this.age); } } function Child(firstname){ this.fname = firstname; this.age = 40; this.saySomeThing = function(){ console.log(this.fname); this.sayAge(); } } Child.prototype = new Parent(); var child = new Child(‘张‘); child.saySomeThing(); </script>
5.采用混合模式实现继承
<script> function Parent(){ this.sayAge = function(){ console.log(this.age); } } Parent.prototype.sayParent = function(){ console.log(‘this is parentmethod!!!‘) } function Child(firstname){ Parent.call(this); this.fname = firstname; this.age = 40; this.saySomeThing = function(){ console.log(this.fname); this.sayAge(); } } Child.prototype = new Parent(); var child = new Child(‘张‘); child.saySomeThing(); child.sayParent(); </script>
原文：http://www.cnblogs.com/xie-zhan/p/6372239.html