https://learn.javascript.ru/classes
Still there are events, there are event listeners. It also need to be processed.
(system WindowsMessaging in Windows and works to inform Windows/field/button on different events between the specified Windows or broadcast events)
Must be the Central class (system), which will be used as a router/arbitrator. It will follow the entire tree of objects and to route events between objects (+log optional).
In other words: this is a common delegate of the parent classes for the child with the event system (subscription, receive, send).