js_question

q1.js

var name = 'window'

var person1 = {
  name: 'person1',
  foo1: function () {
    console.log(this.name)
  },
  foo2: () => console.log(this.name),
  foo3: function () {
    return function () {
      console.log(this.name)
    }
  },
  foo4: function () {
    return () => {
      console.log(this.name)
    }
  }
}

var person2 = { name: 'person2' }

person1.foo4.call(person2)()         // 为什么输出的是'person2'