How to Use OnTreeNodeExpanded Event in Javascript ?

protected void CompleteMenu_TreeNodeExpanded(object sender, TreeNodeEventArgs e)
    {


        string strNodeValue = e.Node.Value;

        if (e.Node.Parent == null)
        {
            foreach (TreeNode node in CompleteMenu.Nodes)
            {
                if (node.Value != strNodeValue)
                    node.Collapse();
            }
        }
        else
        {
            foreach (TreeNode node in e.Node.Parent.ChildNodes)
            {
                if (node.Value != strNodeValue)
                    node.Collapse();
            }
        }
    }