import Notifier from './notifier' ; export function notifierForEvent ( object , eventName ) { if ( object . _eventedNotifiers === undefined ) { object . _eventedNotifiers = { } ; } let notifier = object . _eventedNotifiers [ eventName ] ; if ( ! notifier ) { notifier = object . _eventedNotifiers [ eventName ] = new Notifier ( ) ; } return notifier ; }