记录Javascript集合操作

　　function Set() {
        var items = {};
        /**
         * 添加元素
         * @param {[type]} value [description]
         */
        this.add = function(value) {
            if (!this.has(value)) {
                items[value] = value;
                return true;
            }
            return false;
        };
        /**
         * 删除元素
         * @param  {[type]} value [description]
         * @return {[type]}       [description]
         */
        this.remove = function(value) {
            if (this.has(value)) {
                delete items[value];
                return true;
            }
            return false;
        };
        /**
         * 判断元素是否存在集合里
         * @param  {[type]}  value [description]
         * @return {Boolean}       [description]
         */
        this.has = function(value) {
            return items.hasOwnProperty(value);
        };
        /**
         * 清空集合
         * @return {[type]} [description]
         */
        this.clear = function() {
            items = {};
        };
        /**
         * 获取集合的长度
         * @return {[type]} [description]
         */
        this.size = function() {
            return Object.keys(items).length;
        };
        /**
         * 获取集合的长度（兼容IE8）
         * @return {[type]} [description]
         */
        this.sizeLegacy = function() {
            var count = 0;
            for (var prop in items) {
                if (items.hasOwnProperty(prop))
                    ++count;
            }
            return count;
        };
        /**
         * 获取集合
         * @return {[type]} [description]
         */
        this.values = function() {
            return Object.keys(items);
        };
        /**
         * 获取集合（兼容IE8）
         * @return {[type]} [description]
         */
        this.valuesLegacy = function() {
            var keys = [];
            for (var key in items) {
                keys.push(key);
            }
            return keys;
        };
        /**
         * 并集
         * @param  {[type]} otherSet [description]
         * @return {[type]}          [description]
         */
        this.union = function(otherSet) {
            var unionSet = new Set();

            var values = this.valuesLegacy();
            for (var i = 0; i < values.length; i++) {
                unionSet.add(values[i]);
            }

            values = otherSet.valuesLegacy();
            for (var i = 0; i < values.length; i++) {
                unionSet.add(values[i]);
            }
            return unionSet;
        };
        /**
         * 交集
         * @param  {[type]} otherSet [description]
         * @return {[type]}          [description]
         */
        this.intersection = function(otherSet) {
            var intersectionSet = new Set();

            var values = this.valuesLegacy();
            for (var i = 0; i < values.length; i++) {
                if (otherSet.has(values[i])) {
                    intersectionSet.add(values[i]);
                }
            }

            return intersectionSet;
        };
        /**
         * 差集
         * @param  {[type]} otherSet [description]
         * @return {[type]}          [description]
         */
        this.difference = function(otherSet) {
            var differenceSet = new Set();

            var values = this.valuesLegacy();
            for (var i = 0; i < values.length; i++) {
                if (!otherSet.has(values[i]))
                    differenceSet.add(values[i]);
            }
            return differenceSet;
        };
        /**
         * 子集
         * @param  {[type]} otherSet [description]
         * @return {[type]}          [description]
         */
        this.subset = function(otherSet) {
            if (this.sizeLegacy() > otherSet.sizeLegacy()) {
                return false;
            } else {
                var values = this.valuesLegacy();
                for (var i = 0; i < values.length; i++) {
                    if (!otherSet.has(values[i])) {
                        return false;
                    }
                }
                return true;
            }
        }
    }

    var set = new Set();
    set.add(1);
    set.add(2);
    set.add(3);

    var set1 = new Set();
    set1.add(3);
    set1.add(4);
    set1.add(5);

    var set2 = new Set();
    set2.add(3);

    var unionSet = set.union(set1);
    console.log(unionSet.valuesLegacy());

    var intersectionSet = set.intersection(set1);
    console.log(intersectionSet.valuesLegacy());

    var differenceSet = set.difference(set1);
    console.log(differenceSet.valuesLegacy());

    console.log(set.subset(set1));
    console.log(set2.subset(set));