是否有任何方法添加optgroup标签到依赖的下拉列表与javascript

Question

我确实需要一些关于我的依赖下拉列表的帮助。

我已经找到了这段代码，但我想在subcatagory上添加optgroup标签，试过任何东西，但找不到答案。

感谢，

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>