Global event bus for angular > 2 using rxjs observable and replay subject

event-bus.ts

import {ReplaySubject} from "rxjs/ReplaySubject";
import {Observable} from 'rxjs/Observable';
import "rxjs/add/operator/filter";
import "rxjs/add/operator/map";
import { Injectable } from '@angular/core';

@Injectable()
export class EventBus
{
    private events: {};

    public constructor()
    {
        this.events = {};
    }

    public post(key: any, data?: any): void
    {
        this.addEventIfNotExists(key);

        if (this.events[key])
        {
            this.events[key].next({key, data});
        }
    }

    public on<T>(key: string): Observable<T>
    {
        this.addEventIfNotExists(key);

        return this.events[key]
            .asObservable()
            .filter(event => event.key === key)
            .map(event => <T>event.data);
    }

    public dispose(key: any)
    {
        if (this.events[key] === undefined)
        {
            return;
        }
        this.events[key].unsubscribe();
        delete this.events[key];
    }
    
    public getEvents(): {}
    {
        return this.events;
    }

    public getEventsCount(): number
    {
        let keys:[] = this.events.keys();
        return keys.length;
    }

    private addEventIfNotExists(key: string): void
    {
        if (this.events[key] === undefined)
        {
            this.events[key] = new ReplaySubject<EventBusModel>();
        }
    }
}

interface EventBusModel
{
    key: any;
    data?: any;
}