js 集合的交集、补集、差集、去重

///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);  
                 }  
             } 
         } 
     }
     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"]));