This question

const obj = {
  dev: 'bfe',
  a: function() {
    return this.dev
  },
  b() {
    return this.dev
  },
  c: () => {
    return this.dev
  },
  d: function() {
    return (() => {
      return this.dev
    })()
  },
  e: function() {
    return this.b()
  },
  f: function() {
    return this.b
  },
  g: function() {
    return this.c()
  },
  h: function() {
    return this.c
  },
  i: function() {
    return () => {
      return this.dev
    }
  }
}

console.log(obj.a())
console.log(obj.b())
console.log(obj.c())
console.log(obj.d())
console.log(obj.e())
console.log(obj.f()())
console.log(obj.g())
console.log(obj.h()())
console.log(obj.i()())