用js怎么过滤相同值？

Question

如题：有一个下拉框selectFlag，用js获得下拉框var selectFlag = document.getElementById('selectFlag');
然后遍历该下拉框：for(var i=0;i<selectFlag.length;i++){
             var current = selectFlag.options[i];            
             if(current.value=="all"){ 
             for(var j=0;j<allmember.length;j++){            
             var allList = allmember.options[j];
             if(!radioval.checked){
             if(allList.value==null || allList.value==""){
             idStr += "";
             }else{                          
             idStr += allList.value;
             }
             }else{            
             idStr += allList.value + ",";
             }     
             count += 1;            
             }          
             break;
             }else{            
             if(!radioval.checked){            
             idStr += current.value;
             }else{            
             idStr += current.value + ",";
             }
             count += 1;
             }            
}
把下拉框所有选项的值放到idStr中，怎么把下拉框中相同的选项值过滤掉呢？

Answer 1

提示下思路   if(idStr.indexOf(current.value)!=-1){
      idStr += current.value + ",";
   }
   continue;

Answer 2

不好意思 看错题意了，写反了应该这么：  if(idStr.indexOf(current.value)!=-1){
      continue;
  }else{
     idStr += current.value + ",";  }不知道是不是你要的意思。