NodeExpanding プロパティ

// The client event 'NodeExpanding' takes two parameters sender and e
// sender  is the object which is raising the event
// e is the DataTreeNodeEventArgs
function WebDataTree_NodeExpanding(sender, e) {

    //Gets the node object that is expanding
    var node = e.getNode();

    //Gets the text of the node
    var nodeText = node.get_text();

    if (!confirm("Are you sure you want to expand the node '" + nodeText + "'?"))
    //Cancels the NodeExpanding event
        e.set_cancel(true);

}