class基础语法

ES5声明一个类

let Animal = function (type) {

　　this.type = type

}

Animal.prototype.eat = function () {

　　console.log('eat')

}

ES6声明一个类

class Animal {

　　// 构造函数

　　constructor () {

　　　　this.type = type

　　}

　　eat () {

　　　　console.log('eat')

　　}

}

用class声明类只是ES5声明类的一个语法糖

getter setter可以控制属性的读写

let _age = 1 // 相当于私有属性，外部访问不到
class Animals {
  constructor (kind) {
    this.kind = kind
  }
  get age () {
    return _age
  }
  set age(val) {
    _age = val
  }
  shout () {
    console.log('...')
  }
}

let dog = new Animals('dog')
console.log(dog.age)
dog.age = 2
console.log(dog.age)

 类的静态方法

class Animal {
  constructor (kind) {
    this.kind = kind
  }
  static shout () {
    console.log('这里是类的静态方法')
  }
}
Animal.shout()

// 在ES5里就是 Animal.shout = function () {}

类的继承

// ES5
let Animal = function (kind) {
  this.kind = kind
}

Animal.prototype.shout = function () {
  console.log('...')
}

let Dog = function () {
  // 初始化父类的构造函数
  Animal.call(this, 'dog')
}

Dog.prototype = Animal.prototype

// ES6
class Animal {
  constructor (kind) {
    this.kind = kind
  }
  static shout () {
    console.log('这里是类的静态方法')
  }
}

class Dog extends Animal {
  constructor (kind, color) {
    super(kind)
    this.color = color
  }
}
let dog = new Dog('dog', 'white')
console.log(dog.kind)
console.log(dog.color)

dog
white