代码如下：
要求点击 选择 主菜单后，点击查询按钮
副菜单 中因 对应的是主菜单的 值，
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.3/jquery.min.js"></script>
<script type="text/javascript" language="javascript">
$(function(){
$("#dropLang").unbind("change", eDropLangChange).bind("change", eDropLangChange);
$("#dropFrame").unbind("change", eDropFrameChange).bind("change", eDropFrameChange);
});
var eDropLangChange = function(){
var selectedValue = $(this).val();
$("#dropFrame").children("span").each(function(){
$(this).children().clone().replaceAll($(this));
});
if(parseInt(selectedValue) != 0){
$("#dropFrame").children("option[parentid!='" + selectedValue + "'][value!='0']").each(function(){
$(this).wrap("<span style='display:none'></span>");
});
}
};
var eDropFrameChange = function(){
$("#dropLang").val($(this).children("option:selected").attr("parentid"));
};
</script>
</head>
<body>
<%
String dropLangs="",dropFrame="";
if(request.getParameter("dropLang")!=null&&request.getParameter("dropLang")!=""){
dropLangs=request.getParameter("dropLang");
}
if(request.getParameter("dropFrame")!=null&&request.getParameter("dropFrame")!=""){
dropFrame=request.getParameter("dropFrame");
}
%>
<form action='?' method='post'>
<select id="dropLang" name="dropLang">
<option value="0">請選擇</option>
<option value="1" <%if(dropLangs.equals("1")){out.print("selected");}%>>Javascript</option>
<option value="2" <%if(dropLangs.equals("2")){out.print("selected");}%>>Java</option>
<option value="3" <%if(dropLangs.equals("3")){out.print("selected");}%>>C#</option>
</select>
<select id="dropFrame" name="dropFrame">
<option value="0">請選擇</option>
<option value="1" parentid="1" <%if(dropFrame.equals("1")){out.print("selected");}%>>JQuery</option>
<option value="2" parentid="1" <%if(dropFrame.equals("2")){out.print("selected");}%>>Prototype</option>
<option value="3" parentid="2" <%if(dropFrame.equals("3")){out.print("selected");}%>>Struts</option>
<option value="4" parentid="2" <%if(dropFrame.equals("4")){out.print("selected");}%>>Spring</option>
<option value="5" parentid="2" <%if(dropFrame.equals("5")){out.print("selected");}%>>Velocity</option>
<option value="6" parentid="2" <%if(dropFrame.equals("6")){out.print("selected");}%>>Hibernate</option>
<option value="7" parentid="3" <%if(dropFrame.equals("7")){out.print("selected");}%>>ASP.NET MVC</option>
<option value="8" parentid="3" <%if(dropFrame.equals("8")){out.print("selected");}%>>Castle</option>
</select>
<input type="submit" value="查詢">
</form>
