箭头函数不会修改this

function Person () {
  this.name = 'little bear',
  this.age = 18
  setTimeout(()=>{
	console.log(this
)
})
}
var a = new Person()

setTimeout里的this代表new Person出来的对象

function Person () {
  this.name = 'little bear',
  this.age = 18
  setTimeout(function(){
	console.log(this
)
})
}
var a = new Person()

setTimeout里的this代表window

由于箭头函数不改变this，所以setTimeout里面的箭头函数this，不能改变