js数组去重（多种方法）

 // js数组去重
 Array.prototype.fun1 = function(){
     var arr = this,
         result = [],
         i,
         len = arr.length;
     for(i = 0;i<len;i++){
         if(!(arr[i] in result)){
             result.push(arr[i]);
         }
     }
     return result;
 };
 Array.prototype.fun2 = function(){
     var arr = this,
         i,
         j,
         len = arr.length;
     for(i = 0;i<len;i++){
         for(j = i + 1;j<len;j++){
             if(arr[i] === arr[j]){
                 arr.splice(j, 1);
                 len --;
                 j --;
             }
         }
     }
     return arr;
 };
 Array.prototype.fun3 = function(){
     var arr = this,
         i,
         obj = {},
         result = [],
         len = arr.length;
     for(i = 0;i<len;i++){
         if(!obj[arr[i]]){
             result.push(arr[i]);
             obj[arr[i]] = 1;
         }
     }
     return result;
 };
 Array.prototype.fun4 = function(){
     //数组递归去重
 };
 Array.prototype.fun5 = function(){
     // [...new Set()]
 };
 Array.prototype.fun6 = function(){
     // map, filter
     var arr = this,
         obj = {},
         result = [];
         result = arr.filter((v, k)=>{

         });
     return result;
     // arr.map(function(v, k){
     // });
     // return arr;
 };
 var arr1 = [1,2,3,2];
 arr1.fun1();