JS二级级联下拉菜单

[木叶下521]

有一个二级级联下拉菜单，但是就是不显示，大侠们看看啥问题？

 <tr>
					<td align="right">学院：</td>
					<td><select name="role" onBlur="checkRole(this)" onchange="populateMajor(this.options[this.selectedIndex].value)">
					<option value="0">-请选择学院-</option>
							<%
								List<Department> list = new ArrayList<Department>();
							    DepartmentDao dao = new DepartmentDaoImpl();
									list = dao.findAllDepartments();// 调用实现类的查询全部方法
									for (int i = 0; i < list.size(); i++) {
										Department d = list.get(i);
							%>
							<option value="<%=d.getD_id()%>"><%=d.getD_name()%></option>
							<%
								}
							%>
					</select>
                 <!--级联二级菜单  -->					
					
					<%
								List<MajorAndClass> list1 = new ArrayList<MajorAndClass>();
					            MajorAndClassDao mdao = new MajorAndClassDaoImpl();
									list1 = mdao.findAllMajorAndClass();// 调用实现类的查询全部方法
							%>
					<script type="text/javascript">
					var onecount=0;//定义一个变量，记录Major个数
					var listMajor= new Array();//定义一个数组，记录Major内容
					<%
					int count = 0;//listMajor下标
					for (int i = 0; i < list1.size(); i++) {
						MajorAndClass m = list1.get(i);
					%>
					listMajor[<%=count%>]= new Array(<%=m.getName()%>,<%=m.getM_id()%>,<%=m.getDepartment().getD_id()%>);//把list数据放入listMajor数组
					<%count++;
					
					}%>
					onecount=<%=count%>;
					function populateMajor(dID){//显示二级菜单Major
						document.getElementById("major").options.length=0;
						
					if(dID!=""){
						var dID=parseInt(dID);
					
						for(var i=0;i<onecount;i++)
							{
							if(listMajor[i][2]==dID)
								{
							
								document.getElementById("major").options[i]=new Option[listMajor[i][0],listMajor[i][1]];
								}
							}
					         }
					}
					</script>
					
					</td>
					<td>
					<select id="major" name="major">
						<option value="0" selected>-请选择专业-</option>
					</select>
					</td>
					
				</tr>

效果图：

[求摸小手]

数据获取有没有问题，这个你自己去查。 JS方面有有一处问题： document.getElementById("major").options[i]=new Option[listMajor[i][0],listMajor[i][1]]; 请改成： document.getElementById("major").options[i]=new Option(listMajor[i][0],listMajor[i][1]);

[街头小贩]

最近菜单联动火爆呀。这么多人问

[静静521]

<script type="text/javascript"> 
var  listMajor = new Array(); 
        <% 
        for (int i = 0; i < list1.size(); i++) {
			MajorAndClass m = list1.get(i);
        %> 
        listMajor.push(['<%=m.getName()%>',<%=m.getM_id()%>,<%=m.getDepartment().getD_id()%>]); 
        <% } %> 

function changelocation(dID) 
    { 
	document.getElementById('major').innerHTML =''; 
	var fragment = document.createDocumentFragment(); 
	for(var i =0;i<listMajor.length;i++){ 
	if(listMajor[i][2] == dID) { 
	var option = document.createElement("option"); 
	option.value = listMajor[i][1]; 
	option.innerHTML = listMajor[i][0]; 
	fragment.appendChild(option); 
	} 
	} 

	document.getElementById('major').appendChild(fragment); 
	} 
</script>

楼主看看可以不？