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>