this

Question

What does the code snippet to the right output by console.log?

Snippet

const obj = {
  a: 1,
  b: function() {
    console.log(this.a)
  },
  c() {
    console.log(this.a)
  },
  d: () => {
    console.log(this.a)
  },
  e: (function() {
    return () => {
      console.log(this.a);
    }
  })(),
  f: function() {
    return () => {
      console.log(this.a);
    }
  }
}

console.log(obj.a)
obj.b()
;(obj.b)()
const b = obj.b
b()
obj.b.apply({a: 2})
obj.c()
obj.d()
;(obj.d)()
obj.d.apply({a:2})
obj.e()
;(obj.e)()
obj.e.call({a:2})
obj.f()()
;(obj.f())()
obj.f().call({a:2})

Source

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