HTML+JavaScript实现在一个下拉框中多选，然后提交到另外一个下拉框中的效果

     < html >
     < head >
     < script language = " javascript " >
     function  droplist_submit()
    {
       var  select_instance = document.form1.s1;
       var  select_instance2 = document.form1.s2;
       var  option_length = select_instance.options.length;
       for  (i = 0 ; i < option_length; i ++ )
      {
         if  (select_instance.options[i].selected) {
           var  oOption  =  document.createElement( " OPTION " );
          oOption.text = select_instance.options[i].text;
          oOption.value = select_instance.options[i].value;
          select_instance2.appendChild(oOption);
        }
      }

       //  print new select options to validate the result
       for  (i = 0 ; i < select_instance2.options.length; i ++ )
      {
        alert(select_instance2.options[i].text);
        alert(select_instance2.options[i].value);
      }
    }
     < / script>
     < / head>
     < body >
     < form name = form1 method = post action = " javascript: droplist_submit(); " >
       < select size = 5  name = s1 multiple >
         < option value = " Aoption " > A < / option>
         < option value = " Boption " > B < / option>
         < option value = " Coption " > C < / option>
         < option value = " Doption " > D < / option>
       < / select>

     < p >< / p>
       < select size = 5  name = s2 DISABLED >
       < / select>
     < p >< input type = submit >< / p>
     < / form>
     < / body>
     < / html>