数组去重

1    Array.prototype.unique = Array.prototype.unique || function (){
2        var arr = [];
3        for (var i = 0,len = this.length; i < len; i++){
4            if(arr.indexOf(this[i]) == -1){
5                arr.push(this[i]);
6            }
7        }
8        return arr;
9    };

 1     Array.prototype.unique = Array.prototype.unique || function (){
 2         var arr = [this[0]];
 3         for(var i = 1,len = this.length; i < len; i++){
 4             if(this.indexOf(this[i]) == i){
 5                 arr.push(this[i]);
 6             }
 7         }
 8         return arr;
 9     }; 
10     
11     console.log([1,2,3,5,2,3].unique());  //[1,2,3,5]

 1   Array.prototype.unique = Array.prototype.unique || function (){
 2       var n = {},
 3           arr = [];
 4       for(var i = 0,len = this.length; i < len; i++){
 5           if(!n[this[i]]){
 6               n[this[i]] = true;
 7               arr.push(this[i]);
 8           }
 9       }
10       return arr;
11    };
12    
13    console.log([1,2,3,5,2,3].unique()); //[1,2,3,5]