let obj1 = {
  name: 'oli',
  child: {
    name: 'oliver'
  }
}

let obj2 = {
  [Symbol('name')]: 'alice'
}

let obj3 = Object.defineProperty({}, 'name', {
  value: 'alice',
  enumerable: false
})

let obj4 = Object.create(null)

// 我們需要一個(gè)函數(shù)，判斷是否不含自有屬性

isEmpty(obj1) // false
isEmpty(obj2) // false
isEmpty(obj3) // false
isEmpty(obj4) // true

const isEmptyObj = object => {
  if (!!Object.getOwnPropertySymbols(object).length) {
    return false
  }
  for (const key in object) {
    if (object.hasOwnProperty(key)) {
      return false
    }
  }
  return true
}

const isEmptyObj = object => {
  if (!!Object.getOwnPropertySymbols(object).length) {
    return false
  }
  if (Object.keys(object).length) {
    return false
  }
  return true
}

const isEmptyObj = object => {
  if (!!Object.getOwnPropertySymbols(object).length) {
    return false
  }
  return JSON.stringify(object) === '{}'
}

。

const isEmptyObj = object => {
  if (!!Object.getOwnPropertySymbols(object).length) {
    return false
  }
  if (!!Object.getOwnPropertyNames(object).length) {
    return false
  }
  return true
}

const isEmptyObj = object => !Object.getOwnPropertySymbols(object).length && !Object.getOwnPropertyNames(object).length