anchor.diff:  final FormElement nickForm = querySelector('#nick-form');
   final ButtonElement nickBtn = querySelector('#nick-btn');
   
  -String nick = 'Anonymous user';
  -
   ///
   /// Used to set the nickname in the chat.
   /// [e] is the form submit DOM event.
   /// Nickname can be a default one if the user does not provide one to use.
   ///
  -String handleNickFormSubmit(e) {
  +String handleNickFormSubmit(Event e, JsObject context, InputElement nickInput) {
  +  String nick = 'Anonymous user';
     e.preventDefault();
   
     if (nickInput.value.trim().isNotEmpty) {
  
positive.code: }
  
  void main() {
    // Open the modal window
    context.callMethod('jQuery', ['#nick-modal'])
        .callMethod('modal', []);
  
negative.code: 
    // Handle submission of nickname form
    nickForm.onSubmit.listen((e) {
      nick = handleNickFormSubmit(e, context, nickInput);
    });
  
    // Handle chat message sending
  