• 类和构造函数一样

• 属性和方法分开写的

  // 老版本
  
  function User(name, pass) {
  
      this.name = name
  
      this.pass = pass
  
  }
  
  User.prototype.showName = function () {
  
      console.log(this.name)
  
  }
  
  User.prototype.showPass = function () {
  
      console.log(this.pass)
  
  }
  
  var u1 = new User('able', '1233')
  
  u1.showName()
  
  u1.showPass()
  
  // 老版本继承
  
  function VipUser(name, pass, level) {
  
      User.call(this, name, pass)
  
      this.level = level
  
  }
  
  VipUser.prototype = new User()
  
  VipUser.prototype.constructor = VipUser
  
  VipUser.prototype.showLevel = function () {
  
      console.log(this.level)
  
  }
  
  var v1 = new VipUser('blue', '1234', 3)
  
  v1.showName()
  
  v1.showLevel()

新版面向对象

• 有了 class 关键字、构造器

• class 里面直接加方法

• 继承，super 超类==父类

  class User {
  
      constructor(name, pass) {
  
          this.name = name
  
          this.pass = pass
  
      }
  
      showName() {
  
          console.log(this.name)
  
      }
  
      showPass() {
  
          console.log(this.pass)
  
      }
  
  }
  
  var u1 = new User('able2', '111')
  
  u1.showName()；// able2

  u1.showPass()； // 111
  
  // 新版本继承 
  class VipUser extends User {
   constructor(name, pass, level) {
       super(name, pass) 
       this.level = level 
  } 
   showLevel(){ 
     console.log(this.level) 
   } 
  } 
  v1 = new VipUser('blue', '123', 3) 
  v1.showLevel()；// 3