Would there be any way to retrieve the Children and Second class objects, using the parent class Event?
No. Given just the code you show, there would not be any way to identify all subclasses of Event
in plain Javascript. A parent object is not informed in any way when a subclass is defined, nor is any global catalog maintained. A subclass definition stands on its own and the fact that it subclasses/extends the Event
class is not saved anywhere or registered anywhere. It's just information that is used when an instance of the subclass is actually created.
If you wanted to manually keep track of such a thing, you could create your own catalog of sub-classes and then make your code register everything in that catalog.