Array.prototype.indexOf = IndexOf;
 
//Toggles between two classes for an element
function ToggleClass(element, firstClass, secondClass, event)
{
 event.cancelBubble = true;
 
 var classes = element.className.split(" ");
 var firstClassIndex = classes.indexOf(firstClass);
 var secondClassIndex = classes.indexOf(secondClass);
 
 if (firstClassIndex == -1 && secondClassIndex == -1)
 {
  classes[classes.length] = firstClass;
 }
 else if (firstClassIndex != -1)
 {
  classes[firstClassIndex] = secondClass;
 }
 else
 {
  classes[secondClassIndex] = firstClass;
 }
 
 element.className = classes.join(" ");
 
}
 
//Finds the index of an item in an array
function IndexOf(item)
{
 for (var i=0; i < this.length; i++)
 {  
  if (this[i] == item)
  {
   return i;
  }
 }
 
 return -1;
}
 
//The toggle event handler for each expandable/collapsable node
//- Note that this also exists to prevent any IE memory leaks 
//(due to circular references caused by this)
function ToggleNodeStateHandler(event)
{
 ToggleClass(this, "Collapsed", "Expanded", (event == null) ? window.event : event);
}
 
//Prevents the onclick event from bubbling up to parent elements
function PreventBubbleHandler(event)
{
 if (!event) event = window.event;
 event.cancelBubble = true;
}
 
//Adds the relevant onclick handlers for the nodes in the tree view
function SetupTreeView(elementId)
{
 var tree = document.getElementById(elementId);
 var treeElements = tree.getElementsByTagName("li");
 
 for (var i=0; i < treeElements.length; i++)
 {
  if (treeElements[i].getElementsByTagName("ul").length > 0)
  {
   treeElements[i].onclick = ToggleNodeStateHandler; 
  }
  else
  {
   treeElements[i].onclick = PreventBubbleHandler; 
  }
 }
}