You don't need to use the join method on the array as tracing it will output a comma separated list of values...
js code:
var contacts = new Array();
for (var enum = new Enumerator(Messenger.MyContacts); !enum.atEnd(); enum.moveNext()){
contacts.push(enum.item().Email);
}
Debug.Trace(contacts);
EDIT: Riko15, this is not a chat room or an instant messaging service. As such people may take a while to reply. Please have a little more patience.