ItemRemoved プロパティ

// The client event 'ItemRemoved' takes two parameters sender and e
// sender  is the object which is raising the event
// e is the DropDownControlEventArgs
function WebDropDown_ItemRemoved(sender, e) {
    //Gets the drop-down item that has mouse on it
    var item = e.get_value();

    //Gets the text of the drop-down item
    var text = item.get_text();

    //Gets the index of the drop-down item
    var index = item.get_index();

    alert("Item '" + text + "' with index " + index +" is removed! ");  
}