5种js实现继承的方式实例分享

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();