ItemExpanding Property (DataMenuClientEvents)

// The client event 'ItemExpanding' takes two parameters sender and e
// sender  is the object which is raising the event
// e is the DataMenuItemCancelEventArgs
function WebDataMenu1_ItemExpanding(sender, e) {
    //Gets the DataMenuItem object that is expanding
    var Item = e.getItem();

    //Gets the text of the expanding item

    var ItemText = Item.get_text();

    if (!confirm("Are you sure you want show child items under the item '"+ItemText+"'?"))
           //Cancels the ItemExpanding event
            e.set_cancel(true);


}