Observer.ts

type SubscribedEvent = (...args) => any;

class EventObserver {
    public events: SubscribedEvent[] = [];

    subscribe(fn: SubscribedEvent) {
      this.events.push(fn)
    }

    unsubscribe(fn: SubscribedEvent) {
      this.events = this.events.filter(subscriber => subscriber !== fn)
    }

    emit(data: any) {
      this.events.forEach(subscriber => subscriber(data))
    }
}