code: public function getJavascripts(GetOptionsEvent $event)
      {
          if (($event->getEnvironment()->getDataDefinition()->getName() !== 'tl_metamodel_rendersettings')
              || ($event->getPropertyName() !== 'additionalJs')
              || ($event->getSubPropertyName() !== 'file')) {
              return;
          }
  
          $event->setOptions($this->scanFiles('js'));
      }
docs: Provide options for additional javascript files.
  
  @param GetOptionsEvent $event The event.
  
  @return void