1.对象冒充：

function Parent(username){    this.username = username;    this.hello = function(){         alert(this.username);    }}

function Child(username,password){    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();

2.call()方法：

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();

3.apply()方法：

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();

4.原型链：

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();

5.call()方法与原型链混合：

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();