code: private void newTodo(Event event) {
          if (Key.Enter.match(event)) {
              String text = newTodo.value.trim();
              if (text.length() != 0) {
                  TodoItem item = repository.add(text);
                  list.appendChild(new TodoItemElement(this, repository, item).element());
                  newTodo.value = "";
                  update();
              }
          }
      }
docs: ------------------------------------------------------ event / token handler