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集合的特点
1.无序
2.唯一性
3.不可重复

集合相对于前面几种数据结构，比较简单好理解，看看代码实现就能知道他的用法了

集合的创建

function MySet() {this.item = {};
}
MySet.prototype.has = function (value) {return value in this.item;
};

//增
MySet.prototype.add = function (value) {if (this.has(value)) return false;this.item[value] = value;return true;
};

//删
MySet.prototype.remove = function (value) {if (!this.has(value)) return false;delete this.item[value];return true;
};

//清空
MySet.prototype.clear = function () {this.item = {};
};

//长度
MySet.prototype.size = function () {return Object.keys(this.item).length;
};

//获取值
MySet.prototype.values = function () {let arr = [];console.log("🚀 ~ Object.keys(this.item):", Object.keys(this.item));for (i = 0; i < Object.keys(this.item).length; i++) {const key = Object.keys(this.item)[i];arr.push(this.item[key]);}return arr;
};

//查询
MySet.prototype.print = function () {console.log(this.item);return this.item;
};

//集合的操作

//求并集
MySet.prototype.addUnion = function (data) {let newSet = new MySet();let values = this.values();for (let i = 0; i < values.length; i++) {newSet.add(values[i]);}let values2 = data.values();for (let i = 0; i < values2.length; i++) {newSet.add(values2[i]);}return newSet.values();
};

//求交集

MySet.prototype.interSection = function (data) {const interSection = new MySet();const oldValues = this.values();for (let i = 0; i < oldValues.length; i++) {if (data.has(oldValues[i])) {interSection.add(oldValues[i]);}}return interSection.values();
};

//求差集

MySet.prototype.diff = function (data) {const diff = new MySet();const oldValues = this.values();for (let i = 0; i < oldValues.length; i++) {if (!data.has(oldValues[i])) {diff.add(oldValues[i]);}}return diff.values();
};

测试

const set = new MySet()set.add('a',1)set.add('b',2)console.log(set.print())console.log('values',set.values())//测试求并集const set1 = new MySet()set1.add(1)set1.add(2)set1.add(3)const set2 = new MySet()set2.add(3)set2.add(4)set2.add(5)set2.add(6)set2.add(7)const result = set1.addUnion(set2)console.log(result)  //[1, 2, 3, 4, 5, 6, 7]//求交集const set3 = new MySet()set3.add(1)set3.add(2)set3.add(3)const set4 = new MySet()set4.add(3)set4.add(4)set4.add(5)set4.add(6)const result2 = set3.interSection(set4)console.log("🚀 ~ result2:", result2)//求差集const set5 = new MySet()set5.add(1)set5.add(2)set5.add(3)const set6 = new MySet()set6.add(3)set6.add(4)const result3 = set5.diff(set6)console.log("🚀 ~ result3:", result3)

可以参照着练习下，其实不难，这个知识点！！