code: function onScreenBtnClick (event) {
      const screenId = event.currentTarget.getAttribute('data-screen');
  
      // if the current screen is the same as the clicked one
      if (screenId === screenNavigator.currentItemId) return;
  
      // display the new screen
      screenNavigator.showScreen(screenId);
  }
docs: screenNavigator.transitionType = Transitions.OutAndIn; button click handler