Strikt typisierter Event-Emitter für reaktive Framework-Engines

type EventMap = Record<string, any>;
 
class TypedEmitter<Events extends EventMap> {
  private listeners: {
    [K in keyof Events]?: Array<(payload: Events[K]) => void>;
  } = {};
 
  on<K extends keyof Events>(event: K, listener: (payload: Events[K]) => void): void {
    (this.listeners[event] ??= []).push(listener);
  }
 
  emit<K extends keyof Events>(event: K, payload: Events[K]): void {
    this.listeners[event]?.forEach((cb) => cb(payload));
  }
}
 
interface ApplicationEvents {
  'user:login': { id: string; timestamp: number };
  'cart:checkout': { totalAmount: number };
}
 
const bus = new TypedEmitter<ApplicationEvents>();
bus.on('user:login', (data) => console.log(data.id.toUpperCase()));
bus.emit('user:login', { id: 'u_102', timestamp: Date.now() });