FetchData.scala

@JSExport
def main(target: html.Div): Unit = {
  ...
  fetchData().onSuccess {
    case s =>
      thingsToDo = read[List[Task]](s.responseText)
      // now you need to refresh the UI
  }
  def fetchData() = Ajax.get("https://sizzling-torch-788.firebaseio.com/dummyTask.json")
  ...
}