上拉菜单跳转页面 _Web前端

下拉菜单跳转页面
    <script language="javascript">
   function sub(sum){
   document.form1.action="manage.jsp?page="+sum;
   document.form1.submit();

   }
</script>
<html>
<head>
    <title>My JSP 'manage.jsp' starting page</title>

</head>

<body>

<form action="" method="post" id="form1" name="form1">
    <table width="800" border="0" align="center" cellpadding="0" cellspacing="0">
<tr>
    <td>
         <select name="which" id="which" onchange="sub(this.options[this.selectedIndex].value);">

         <option value="1" >1</option>

         <option value="2" >2</option>
<option value="3" selected>3</option>

         <option value="4" >4</option>

         </select>

    </td>

    </tr>

</table>
</form>
</body>
</html>