Tree view expand collapse functionality?

Question

I want to add expand & collapse functionality in the tree view list..how to add this? I have added the jqueries required. . .

<div id="sidetree">
   <div class="company">Company</div>
   <div id="sidetreecontrol" class="sidetreecontrol"></div>
   <ul class="treeview" id="tree">
      <li><a href="#">Home</a></li>
      <li class="expandable">
         <div class="hitarea expandable-hitarea"></div>
         <span><strong>About Us</strong></span>
         <ul style="display: none;">
            <li><a href="#">Our Offers</a></li>
            <li class="last"><a href="#">Our Offers</a></li>
         </ul>
      </li>
   </ul>
</div>

Answer 1

I think adding

<a href="?#">Collapse All</a> | <a href="?#">Expand All</a>

should do the trick.