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js继承有5种实现方式： 

function Parent(username){     this.username = username;     this.hello = function(){       alert(this.username);     }   }   function Child(username,password){     //通过以下3行实现将Parent的属性和方法追加到Child中，从而实现继承     //第一步：this.method是作为一个临时的属性，并且指向Parent所指向的对象，     //第二步：执行this.method方法，即执行Parent所指向的对象函数     //第三步：销毁this.method属性，即此时Child就已经拥有了Parent的所有属性和方法     this.method = Parent;     this.method(username);//最关键的一行     delete this.method;     this.password = password;     this.world = function(){       alert(this.password);     }   }   var parent = new Parent("zhangsan");   var child = new Child("lisi","123456");   parent.hello();   child.hello();   child.world(); 

function test(str){     alert(this.name + " " + str);   }   var object = new Object();   object.name = "zhangsan";   test.call(object,"langsin");//此时，第一个参数值object传递给了test类(即方法)中出现的this，而第二个参数"langsin"则赋值给了test类(即方法)的str   function Parent(username){     this.username = username;     this.hello = function(){       alert(this.username);     }   }   function Child(username,password){     Parent.call(this,username);         this.password = password;     this.world = function(){       alert(this.password);     }   }   var parent = new Parent("zhangsan");   var child = new Child("lisi","123456");   parent.hello();   child.hello();   child.world(); 

function Parent(username){     this.username = username;     this.hello = function(){       alert(this.username);     }   }   function Child(username,password){     Parent.apply(this,new Array(username));         this.password = password;     this.world = function(){       alert(this.password);     }   }   var parent = new Parent("zhangsan");   var child = new Child("lisi","123456");   parent.hello();   child.hello();   child.world(); 

function Person(){   }   Person.prototype.hello = "hello";   Person.prototype.sayHello = function(){     alert(this.hello);   }     function Child(){   }   Child.prototype = new Person();//这行的作用是：将Parent中将所有通过prototype追加的属性和方法都追加到Child，从而实现了继承   Child.prototype.world = "world";   Child.prototype.sayWorld = function(){     alert(this.world);   }     var c = new Child();   c.sayHello();   c.sayWorld(); 

function Parent(hello){     this.hello = hello;   }   Parent.prototype.sayHello = function(){     alert(this.hello);   }   function Child(hello,world){     Parent.call(this,hello);//将父类的属性继承过来     this.world = world;//新增一些属性   }   Child.prototype = new Parent();//将父类的方法继承过来   Child.prototype.sayWorld = function(){//新增一些方法     alert(this.world);   }   var c = new Child("zhangsan","lisi");   c.sayHello();   c.sayWorld();

js原型和继承详解

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