Code

function onNodeDeleting(sender, args)
{
	deleteDescendants(args.getNode());
}

function deleteDescendants(node)
{
	var links = node.getOutgoingLinks().slice();
	links.forEach(function (link)
	{
		var child = link.getDestination();
		deleteDescendants(child);
		child.parent.removeItem(child);
	});
} 

Code

function onNodeDeleting(sender, args)
{
	var node = args.getNode();
	if (node.children)
		deleteContent(node);
}

function deleteContent(container)
{
	var children = container.children.slice();
	children.forEach(function (child)
	{
		if (child.children)
			deleteContent(child);
		child.parent.removeItem(child);
	});
}