javascript继承方式
1.对象冒充
function Parent(username){this.username = username;this.sayHello = function(){alert("hello,"+this.username);}}function Child(username,password){ //三行重要代码this.method = Parent;this.method(username);delete this.method;this.password = password;this.sayWorld = function(){alert("world,"+this.password);}}var parent = new Parent("wlh");var child = new Child("wlh_child","111111");parent.sayHello();child.sayHello();child.sayWorld();

2.call方法方式：call方法是Function对象中的一个方法,因此我们定义的每个函数都拥有该方法。可以通过函数名来调用call方法，call方法的第一个参数会被传递给函数中的this,从第二个参数开始，逐个赋值给函数中的参数。
1)call方法使用方式：
function test(str,str2){alert(this.name + "," +str + "," +str2);}var object = new Object();object.name = "wlh";//相当于调用了test函数test.call(object,"wlhs");//将object赋给了this

结果：
wlh,wlhs,undefined
2）call方法继承

function Parent(username){          this.username = username;          this.sayHello = function(){              alert("hello,"+this.username);          }      }      function Child(username,password){  Parent.call(this,username);this.password = password;this.sayWorld = function(){              alert("world,"+this.password);          }  }var parent = new Parent("wlh");      var child = new Child("wlh_child","111111");      parent.sayHello();        child.sayHello();      child.sayWorld();  

function Parent(username){          this.username = username;          this.sayHello = function(){              alert("hello,"+this.username);          }      }      function Child(username,password){  Parent.apply(this,new Array(username));this.password = password;this.sayWorld = function(){              alert("world,"+this.password);          }  }var parent = new Parent("wlh");      var child = new Child("wlh_child","111111");      parent.sayHello();        child.sayHello();      child.sayWorld();  

function Parent(){}Parent.prototype.username = "wlh";Parent.prototype.getUsername = function(){alert(this.username);}function Child(){}Child.prototype = new Parent();Child.prototype.password = "111111";Child.prototype.getPassword = function(){alert(this.password);}var child = new Child();child.getUsername();child.getPassword();

function Parent(username){this.username = username;}Parent.prototype.getUsername = function(){alert(this.username);}function Child(username,password){Parent.call(this,username);this.password = password;}Child.prototype = new Parent();Child.prototype.getPassword = function(){alert(this.password);}var child = new Child("wlh","111111");child.getUsername();child.getPassword();