实现一个 Set 的 polyfill

[lovelmh13]

const MySet = function (iterator) {
  this._value = []
  this.size = 0

  init = () => {
    if (iterator[Symbol.iterator]) {
      for (const [index, item] of iterator.entries()) {
        this.add(item)
      }
    } else {
      throw new TypeError(
        `${typeof iterator} is not iterable (cannot read property Symbol(Symbol.iterator))`
      )
    }
  }

  init()
}

MySet.prototype.add = function (value) {
  if (this._value.indexOf(value) === -1) {
    // 保证了唯一性
    this._value.push(value)
    this.size++
  }
  return this // 返回 this 本身
}

MySet.prototype.has = function (value) {
  return this._value.indexOf(value) !== -1
}

MySet.prototype.delete = function (value) {
  const index = this._value.indexOf(value)
  if (index !== -1) {
    this._value.splice(index, 1)
    this.size--
    return true
  } else {
    return false
  }
}

// 还有一些方法，暂时没有实现

// -------------- 测试 --------------
const bar = ['a', 'b', 'c', 'd']
const bar1 = ['a1', 'b1', 'c1', 'd1']

const res1 = new MySet(bar)
console.log(res1)

// const res2 = new MySet(bar1)
// res2.add('e1')
// console.log('res2: ', res2)
// console.log('res1: ', res1)
res1.delete('c')
console.log(res1)

// https://juejin.cn/post/6844903639962632200#heading-0