javascript操作html中select的上下移动

手写getSelectItem、getSelectItemIndex方法
 

function setToFirst(list){          
        var obj=getSelectItem(list);     
        var index=getSelectItemIndex(list);
        if(index==0){return;}
        list.add(new Option(obj.innerText,obj.value),0);
        list.remove(list.length-1);                             
               
        list.selectedIndex=0;
  }
 
  function setToLast(list){
        var obj=getSelectItem(list);     
        var index=getSelectItemIndex(list);
        if(index==list.length-1){return;}                                     
        list.add(new Option(obj.innerText,obj.value),list.length);       
        list.remove(getSelectItemIndex(list));
        list.selectedIndex=list.length-1;
  }
 
  function setToUp(list){
        var index=getSelectItemIndex(list);
        var obj=getSelectItem(list);   
        if(index>0){
            list.add(new Option(obj.innerText,obj.value),index-1);
            list.remove(index+1);
            list.selectedIndex=index-1;
        }
  }
 
  function setToDown(list){
        var index=getSelectItemIndex(list);
        var obj=getSelectItem(list);   
        if(index<list.length-1){
            list.add(new Option(obj.innerText,obj.value),index+2);
            list.remove(index);
            list.selectedIndex=index+1;
        }
  }

 

其实实现这些使用jQuery是相当简单的，以前自己会写这么去写