大厂this面试题和箭头函数的this指向

1. this 

var name=222
var a={
  name:111,
  say:function(){
    console.log(this.name)
  }
}
 
var fun=a.say
fun() //fun.call(window) //222
a.say() //a.say.call(a) //111
 
var b={
  name:333,
  say:function(fn){
    fn()
  }
}
b.say(a.say) //fn() fun.call(window) //222
b.say=a.say //把a里的say函数直接赋值给b.say
b.say() //b.say.call(b) //333

通过使用call来确定this指向。 

2. 箭头函数的this指向