js 数组去重复的方法

数组去重复是js中常用的方法，归纳了四种如下：

1. for + indexOf  去重复

       var arr = [3,5,5,4,1,1,2,3,7,2,5];
       var target = [];
       for(var i=0,len=arr.length;i<len;i++){
         if( target.indexOf(arr[i])==-1 ){
           target.push(arr[i]);
         }
       };
       console.log(target);

2. forEach + indexOf 去重复

       var arr = [3,5,5,4,1,1,2,3,7,2,5];
       var target = [];
       arr.forEach(function(val){
         if(this.indexOf(val)==-1){
           this.push(val);
         };
       },target);
       console.log(target);

3.原型对象 prototype + for + indexOf 去重复

       Array.prototype.quchong = function(){
         var target = [] ;
         for(var i=0,len=this.length;i<len;i++){
           if(target.indexOf(this[i])==-1){
             target.push(this[i]);
           }
         };
         return target;
       };
       var arr = [3,5,5,4,1,1,2,3,7,2,5];
       console.log(arr.quchong());

4.原型对象 prototype + forEach + indexOf 去重复

       Array.prototype.quchong = function(){
         var target = [];
         this.forEach(function(val){
           if(this.indexOf(val)==-1){
             this.push(val);
           }
         },target);
         return target;
       };
       var arr = [3,5,5,4,1,1,2,3,7,2,5];
       console.log(arr.quchong());

运行结果：