1. 使用对象冒充实现继承

function Person(username){    this.username=username;    this.sayHello=function(){        alert(this.username);    }}function Child(username,password){    this.superUserName=Person;    this.superUserName(username);    delete this.superUserName;        this.sayWord=function(){        alert(password);    }}var a=new Person('a');a.sayHello();var b=new Child('b','2b');b.sayHello();b.sayWord();

2. 使用Function的call方法

function Person(username){    this.username=username;    this.sayHello=function(){        alert(this.username);    }}function Child(username,password){    Person.call(this,username);        this.sayWord=function(){        alert(password);    }}var a=new Person('a');a.sayHello();var b=new Child('b','2b');b.sayHello();b.sayWord();

3.使用Function的apply方法

function Person(username){    this.username=username;    this.sayHello=function(){        alert(this.username);    }}function Child(username,password){    Person.apply(this,[username]);        this.sayWord=function(){        alert(password);    }}var a=new Person('a');a.sayHello();var b=new Child('b','2b');b.sayHello();b.sayWord();

4.原型方式实现继承(无法实现参数传递)

function Person(){}Person.prototype.username='hello';Person.prototype.sayHello=function(){    alert(this.username);}function Child(){    }Child.prototype=new Person();Child.prototype.password='word';Child.prototype.sayWord=function(){    alert(this.password);}var a=new Person();a.sayHello();var b=new Child();b.sayHello();b.sayWord();

5.原型混合方式实现继承

function Person(username){    this.username=username;}Person.prototype.sayHello=function(){    alert(this.username);}function Child(username,password){    this.password=password;    Person.call(this,username);}Child.prototype=new Person();Child.prototype.sayWord=function(){ //放在new Person后面，不然会被覆盖    alert(this.password);}var a=new Person('a');a.sayHello();var b=new Child('b','2b');b.sayHello();b.sayWord();