编辑代码

// 集合 无序不重复的一种数据结构

class MockSet {
    constructor() {
        this.items = {}
    }

    add(element) {
        if(!has(element)) {
            Object.assign(this.items, element);
        }
    }

    delete() {
        // delete ...
    }

    size() {
        return Object.keys(this.items).length;
    }

    values() {
        return Object.values(this.items);
    }

    clear() {
        this.items = {};
    }

    has(element) {
        return Object.prototype.hasOwnProperty.call(this.items, element)
    }
}

// union 两个
//intersection has
// difference !has
// subSet loop every has if any one no then no