有没有办法用javascript将optgroup标签添加到依赖下拉列表中

Question

我确实需要一些关于我的依赖下拉列表的帮助。

我找到了此代码，但我想在子类别中添加 optgroup 标签，尝试了任何方法但找不到答案。

谢谢，

    case "Home Ware" :
    <optgroup label="Fruits">;
document.formname.subcategory.optgroup      
 document.formname.subcategory.options[0]=new Option("Select Sub-Category","");
 document.formname.subcategory.options[1]=new Option("Air-Conditioners/Coolers","Air-Conditioners/Coolers");
 document.formname.subcategory.options[2]=new Option("Audio/Video","Audio/Video");
 document.formname.subcategory.options[3]=new Option("Beddings","Beddings");
 document.formname.subcategory.options[4]=new Option("Camera","Camera");
 document.formname.subcategory.options[5]=new Option("Cell Phones","Cell Phones");

Answer 1

 <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
 <script language="javascript" type="text/javascript">
 function dropdownlist(listindex)
 {

document.formname.subcategory.options.length = 0;
 switch (listindex)
 {

 case "Home Ware" :
    <optgroup label="Fruits">;
document.formname.subcategory.optgroup      
 document.formname.subcategory.options[0]=new Option("Select Sub-Category","");
 document.formname.subcategory.options[1]=new Option("Air-Conditioners/Coolers","Air-Conditioners/Coolers");
 document.formname.subcategory.options[2]=new Option("Audio/Video","Audio/Video");
 document.formname.subcategory.options[3]=new Option("Beddings","Beddings");
 document.formname.subcategory.options[4]=new Option("Camera","Camera");
 document.formname.subcategory.options[5]=new Option("Cell Phones","Cell Phones");


 break;

 case "Education" :
 document.formname.subcategory.options[0]=new Option("Select Sub-Category","");
 document.formname.subcategory.options[1]=new Option("Colleges","Colleges");
 document.formname.subcategory.options[2]=new Option("Institutes","Institutes");
 document.formname.subcategory.options[3]=new Option("Schools","Schools");
 document.formname.subcategory.options[4]=new Option("Tuitions","Tuitions");
 document.formname.subcategory.options[5]=new Option("Universities","Universities");

 break;

 case "Books" :
 document.formname.subcategory.options[0]=new Option("Select Sub-Category","");
 document.formname.subcategory.options[1]=new Option("College Books","College Books");
 document.formname.subcategory.options[2]=new Option("Engineering","Engineering");
 document.formname.subcategory.options[3]=new Option("Magazines","Magazines");
 document.formname.subcategory.options[4]=new Option("Medicine","Medicine");
 document.formname.subcategory.options[5]=new Option("References","References");
  document.getElementById("optg1").label = "first group";
 break;

 }
 return true;
 }

 </script>


<form id="formname" name="formname" method="post" action="submitform.asp" >
 <table width="50%" border="0" cellspacing="0" cellpadding="5">
 <tr>
 <td width="41%" align="right" valign="middle">Category :</td>
 <td width="59%" align="left" valign="middle"><select name="category" id="category" onchange="javascript: dropdownlist(this.options[this.selectedIndex].value);">

 <option value="">« Select Services »</option>
 <option value="Home Ware">Personalized Facilitation Services</option>
 <option value="Education">Medical Second Opinion Services</option>

 </select></td>
 </tr>
 <tr>
 <td align="right" valign="middle">Sub Category :
 </td>
 <td align="left" valign="middle"><script type="text/javascript" language="JavaScript">
 document.write('<select name="subcategory"><option value="">Select Sub-Category</option></select>')
 </script>
 <noscript><select name="subcategory" id="subcategory" >
 <option value="">« Select Expertise »</option>
 </select>
 </noscript></td>
 </tr>
 </table>

</form>