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：