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最劲项目需要用到js数组去重和交集的一些运算，我的数组元素个数可能到达1000以上，网上的实现方式都是2次循环，性能不适合我的需求，1000*1000那次数太多了，所以我这里采用对象object来做处理，用空间换时间，code 如下：

        ///集合取交集
        Array.intersect = function () {
            var result = new Array();
            var obj = {};
            for (var i = 0; i < arguments.length; i++) {
                for (var j = 0; j < arguments[i].length; j++) {
                    var str = arguments[i][j];
                    if (!obj[str]) {
                        obj[str] = 1;
                    }
                    else {
                        obj[str]++;
                        if (obj[str] == arguments.length)
                        {
                            result.push(str);
                        }
                    }//end else
                }//end for j
            }//end for i
            return result;
        }

        //集合去掉重复
        Array.prototype.uniquelize = function () {
            var tmp = {},
                ret = [];
            for (var i = 0, j = this.length; i < j; i++) {
                if (!tmp[this[i]]) {
                    tmp[this[i]] = 1;
                    ret.push(this[i]);
                }
            }

            return ret;
        }
        //并集
        Array.union = function () {
            var arr = new Array();
            var obj = {};
            for (var i = 0; i < arguments.length; i++) {
                for (var j = 0; j < arguments[i].length; j++)
                {
                    var str=arguments[i][j];
                    if (!obj[str])
                    {
                        obj[str] = 1;
                        arr.push(str);
                    }
                }//end for j
            }//end for i
            return arr;
        }

        //2个集合的差集 在arr不存在
        Array.prototype.minus = function (arr) {
            var result = new Array();
            var obj = {};
            for (var i = 0; i < arr.length; i++) {
                obj[arr[i]] = 1;
            }
            for (var j = 0; j < this.length; j++) {
                if (!obj[this[j]])
                {
                    obj[this[j]] = 1;
                    result.push(this[j]);
                }
            }
            return result;
        };

        console.log(Array.intersect(["1", "2", "3"], ["2", "3", "4", "5", "6"]));//[2,3]
        console.log([1, 2, 3, 2, 3, 4, 5, 6].uniquelize());//[1,2,3,4,5,6]
        console.log(Array.union(["1", "2", "3"], ["2", "3", "4", "5", "6"], ["5", "6", "7", "8", "9"]))
        console.log(["2", "3", "4", "5", "6"].minus(["1", "2", "3"]));