anchor.diff:    void handleStatusChange(Map status) {
       isOnline.set(status['isOnline']);
     }
  -  
  +
     useEffect(() {
       ChatAPI['subscribeToFriendStatus'](friendID, handleStatusChange);
       return () {
  
positive.code: }
  
  final ChatAPI = {
    'subscribeToFriendStatus': (int id, Function handleStatusChange) => handleStatusChange({'isOnline': id % 2 == 0 ? true : false}),
    'unsubscribeFromFriendStatus': (int id, Function handleStatusChange) => handleStatusChange({'isOnline': false}),
  };
  
  
negative.code: _friendListItem(Map props) {
    final isOnline = useFriendStatus(props['friend']['id']);
  
    return react.li({
      'style': {'color': isOnline.value ? 'green' : 'black'}
    }, [
      props['friend']['name']
    ]);
  }
  
  void main() {
  