anchor.diff:  }
   
   void main() {
  +  String nick;
  +
     // Open the modal window
     context.callMethod('jQuery', ['#nick-modal'])
         .callMethod('modal', []);
  
positive.code: 
    // Handle submission of nickname form
    nickForm.onSubmit.listen((e) {
      nick = handleNickFormSubmit(e);
    });
  
    // Handle chat message sending
  
negative.code: final FormElement nickForm = querySelector('#nick-form');
  final ButtonElement nickBtn = querySelector('#nick-btn');
  
  ///
  /// 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(Event e, JsObject context, InputElement nickInput) {
    String nick = 'Anonymous user';
    e.preventDefault();
  
    if (nickInput.value.trim().isNotEmpty) {
  