js自动生成下拉框

<tr>
      <td height="35" align="center" valign="middle" bgcolor="#F5F5F5">选择商品类型：</td>
      <td height="35" align="left" valign="middle" class="pl-5">
      <select id="product_sort_id_one" name="product_sort_id_one"  url="${path}/ProductSort/list/listSelect?sortid=0"  selectedValue="201107061629033474" prompt="请选择商品类型" childId="product_id_4" childDataPath="${path}/ProductChe/list/listSelect/sort?product_sort_id_one=" ></select>
      </td>
       <td height="35" align="center" valign="middle" bgcolor="#F5F5F5">选择商品：</td>
      <td height="35" align="left" valign="middle" class="pl-5">
      <select id="product_id_4" name="product_name_4" prompt="请选择商品" onchange="addNewForm()"  class="validate[required]" ></select>
      </td>
      <td height="35" align="center" valign="middle" bgcolor="#F5F5F5">预计商品数量：</td>
      <td height="35" align="left" valign="middle" class="pl-5">
      <input type="text" id="product_number_fr"  name="product_number_fr" class="validate[required] float_left" value="250"/>
      <span class="star float_left"></span>
        <div class="validation_info"></div>
        <div class="clear"></div>
      </td>
    </tr>

js方法
<script type="text/javascript">
function addNewForm(){
var $jtable=$j('<table width="98%" border="0" align="center" cellpadding="0" cellspacing="0" class=" tablestyle"><tr><td width="10%" height="35" align="center" valign="middle" bgcolor="#F5F5F5">选择商品类型：</td><td width="20%" height="35" align="left" valign="middle" class="pl-5"></td><td width="10%" height="35" align="center" valign="middle" bgcolor="#F5F5F5">选择商品：</td><td width="20%" height="35" align="left" valign="middle" class="pl-5"></td><td width="10%" height="35" align="center" valign="middle" bgcolor="#F5F5F5">预计商品数量：</td><td width="30%" height="35" align="left" valign="middle" class="pl-5"></td></tr></table>')
$j("#testBtn").after($jtable);
$jtable.find("table").render();
var $jproduct_sort_id_one = $j('<select id="product_sort_id_one" name="product_sort_id_one" url="${path}/ProductSort/list/listSelect?sortid=0" prompt="请选择商品类型" childId="product_id_5" childDataPath="${path}/ProductChe/list/listSelect/sort?product_sort_id_one=" ></select>');
var $jproduct_id_tu=$j('<select id="product_id_5" name="product_name_5" prompt="请选择商品"  ></select>');
var $jproduct_number_tu=$j('<input type="text" id="product_number_tu" name="product_number_tu"  value="0"  class="validate[required] float_left"/>');
$jtable.find("tr").eq(0).find("td").eq(1).append($jproduct_sort_id_one);
$jtable.find("tr").eq(0).find("td").eq(3).append($jproduct_id_tu);
$jtable.find("tr").eq(0).find("td").eq(5).append($jproduct_number_tu);
$jproduct_sort_id_one.render();
$jproduct_id_tu.render();
$jproduct_number_tu.render();
}
</script>