使用JQuery控制某个标签的class

<input type="hidden" id="hidId" name="hidId" value="${ id }" />
<ul id="tiezi">
<%
int i = 0;
List<ProblemBean> problemList = (List<ProblemBean>)request.getAttribute("problemlist");
if(null != problemList && problemList.size()>0){
for(ProblemBean item : problemList){
i++;
%>
<li>
<h4 id="<%=item.getId() %>" class="off"><%=i %>、<%=item.getTitle() %></h4>
<div class="con1">
<div class="answer">
<p><%=item.getAnswer() %></p>
</div>
</div>
</li>
<%}
} %>
</ul>

jQuery(document).ready(function () {
var id = document.getElementById("hidId").value;
if(id != ""){
var obj = jQuery('h4[id='+id+']');
obj.removeClass();
obj.addClass('on');
obj.next().show();
}
});