笔试题--JS中的this

getThisRes.js

var name = 0;
var a = {
  name: 1,
  f1: function(){
    this.name = 2;
  },
  f2: function(){
    this.name = 3;
    return null
  },
  f3: function(){
    this.name = 4;
    return {}
  },
  f4: function(){
    var name = 5;
    console.log(this.name);
  },
  f5: () => {
    var name = 6;
    console.log(this.name);
  }
}

var o1 = new a.f1;
console.log(o1.name); // 2

var o2 = new a.f2();
console.log(o2.name); // 3

var o3 = new a.f3;
console.log(o3) // 因为f3中return了{}，此时会正常返回{}，所以o3.name就是undefined
console.log(o3.name); // undefined

a.f4(); // 1
f4 = a.f4;
f4(); // 0
f4.call(a); // 1

console.log(a.f5) // 因为a.f5会返回这个箭头函数() => {var name = 6;console.log(this.name);}，而此时箭头函数中的this指向了window，所以a.f5()会返回0
a.f5(); // 0