docs: function SetArr() {
    let arr = {}
    let set = {
      size: 0,
      clear() {
        set.size = 0
      },
      add(item) {
        let index = arr.indexOf(item)
        if (index !== -1) return arr
        arr.push(item)
        set.size = arr.length
        return set
      },
      delete(item) {
        let index = arr.indexOf(item)
        if (index === -1) return false
        arr.splice(index, 1)
        set.size = arr.length
        return true
      },
      [Symbol.iterator]: () => arr[Symbol.iterator]()
    }
    return set
  }