实现 es6 中的 Set

Question

class MySet {
    constructor(iterator = []) {
        if (typeof iterator[Symbol.iterator] !== 'function') {
            throw new Error('arguments must be iteratorable')
        }
        this._data = []
        for (const item of iterator) {
            this.add(item)
        }
    }

    add(data) {
        if (!this.has(data)) {
            this._data.push(data)
        }
    }
    has(data) {
        for (const idx in this._data) {
            const item = this._data[idx]
            if (this.isEqual(item, data)) {
                this._data.splice(idx, 1)
                return true
            }
        }
        return false
    }
    clear() {
        this._data.length = 0
    }
    forEach(callback, thisArg) {
        for (const item of this._data) {
            callback.call(thisArg, item, item, this)
        }
    }
    get size() {
        return this._data.length
    }


    delete(data) {
        for (const item of this._data) {
            if (this.isEqual(item, data)) {
                return true
            }
        }
    }
   *[Symbol.iterator]() {
      for (const item of this._datas) {
        yield item
      }
    }

    isEqual(a, b) {
        // NaN
        if (a !== a && b !== b) {
            return true
        }
        return a === b

    }
}