js实现继承的5种方式

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strfunction 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();