bind、call、apply

this 指向谁
var name = "freemen"
function sayAuthor(){
  var name = 'mkw'
  console.log(`this.name`,this.name)
}
sayAuthor()              //freemen
window.sayAuthor() //freemen




//小王去面试
//小王去招聘会现场参加面试 招聘的企业是腾讯和阿里
//腾讯和阿里的面试官分别是 freemen 和 vinko ,阿里的vinko 临时有事请腾讯的fenmen来帮忙
//freemen 来到阿里的面试现场 谁  你好 我是vinko 我的公司是阿里



const Tencent = {
  name:"freemen",
  company:"Tencent",
  time:"2021-11-31",
  address:"BeiJing",
  say(company){
     console.log(`my name is`,this.name)
     console.log(`my company is`,company)
  }
}

const Alibaba = {
  name:"Vinko",
  time:"2021-11-31",
  address:"BeiJing",
  say(company){
     console.log(`my name is`,this.name)
     console.log(`my company is`,company)
  }
}


Tencent.say('Tencent')
\\ my name is Tencent 
\\my company is Tencent

//freemen 替 vinko 面试
Tencent.say.call(Alibaba,'Alibaba')
//my name is Vinko
//my company is Alibaba
Tencent.say.apply(Alibaba,['Alibaba'])

const say = Tencent.say.bind(Alibaba,'Alibaba')
say()


//总结
//call 和 apply 传参方式不同
//bind返回值是函数 和 call 传参一样 

使用场景
//判断数据类型
const array = [1,2,3,4]
const type = Object.prototype.toString.call(array)

类 数组:
const arrayLike = {
 0：“name”,
 1:   “age”，
  2：“gender”，
  length:3
}
const res = Array.prototype.slice.call(arrayLike)
['name','age','gender']