面試總結 - 基礎編程 - 實現繼承3.js

用es5實現一個繼承

類式繼承

function Person () {
  this.name = 'Person'
  this.sex = 'male'
  this.say = function () {
    console.log('Person say')
  }
}

function Student () {
  Person.call(this) // 問題關鍵，改變執行上下文
  this.name = 'Student'
  this.privateAttr = '學生類的私有屬性'
  this.say = function () {
    console.log('Student say')
  }
}

var stu = new Student()
var person = new Person()

原型繼承

function Animal () {
  this.name = 'Animal'
  this.sex = 'male'
}
Animal.prototype.say = function () {
  console.log('Animal Say')
}
function Pig () {
  this.name = 'Pig'
  this.privateAttr = '豬的私有屬性'
}
Pig.prototype = new Animal()
Pig.prototype.constructor = Pig
Pig.prototype.eat = function () {
  console.log(`${this.name} eat`)
}

var pig = new Pig()
var animal = new Animal()

組合繼承

function Fe () {
  this.name = 'Fe'
  this.zhName = '鐵'
}
Fe.prototype.say = function () {
  console.log(this.name)
}
function Fe3O4 () {
  Fe.call(this)
  this.name = 'Fe3O4'
  this.privateAttr = '四氧化三鐵 的私有屬性'
}
Fe3O4.prototype = new Fe()
Fe3O4.prototype.constructor = Fe3O4

var fe3o4 = new Fe3O4()
var fe = new Fe()

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