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;
}
}
}