js差集 ，并集，交集等

交集

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;
        }

console.log(Array.intersect(["1", "2", "3"], ["2", "3", "4", "5", "6"]));//[2,3]

数组对象取交集

var a = [
      { id: "001", name: "zhangsan" },
      { id: "002", name: "tom" },
      { id: "003", name: "jack" },
      { id: "004", name: "fei" },
      { id: "005", name: "ming" }
    ];
    var b = [
      { id: "003", name: "jack" },
      { id: "005", name: "ming" },
      { id: "007", name: "hello" },
      { id: "008", name: "milk" }
    ];
    var obj={};
    var arr=a.concat(b);
    arr.reduce(function(pre, cur) {
      obj.hasOwnProperty(cur.id) ? pre.push(cur) : (obj[cur.id] = cur);
      return pre;
    }, []);
    console.log(Object.values(obj))

 去重

去重
        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;
        }
console.log([1, 2, 3, 2, 3, 4, 5, 6].uniquelize());//[1,2,3,4,5,6]

 并集

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

交集

arr1=[1,2,3] arr2=[2,3,4]

var arr3 = arr2.filter(function(v){
            return arr1.indexOf(v)!==-1 // 利用filter方法来遍历是否有相同的元素
        })

差集

var result = arr2.concat(arr3 ).filter(function (v) {
                return arr2.indexOf(v)===-1 || arr3 .indexOf(v)===-1
            })