event manager in pure js

event-manager.ts

type Listener<T = any> = () => Promise<T> | T;

class EventManager {
  protected listeners: Record<string, Listener[]> = {};

  public on<T = any>(eventName: string, listener: Listener<T>) {
    if (typeof this.listeners[eventName] !== 'object') {
      this.listeners[eventName] = [];
    }

    this.listeners[eventName].push(listener);

    return listener;
  }

  public emit(eventName: string, ...args: any[]) {
    if (typeof this.listeners[eventName] !== 'object') {
      return;
    }

    this.listeners[eventName].forEach(listener => {
      try {
        listener.apply(this, args);
      } catch {
        throw new Error(`Error while emitting event ${eventName}`);
      }
    });
  }

  public remove(eventName: string, listener: Listener) {
    if (typeof this.listeners[eventName] !== 'object') {
      return;
    }

    const listenerIndex = this.listeners[eventName].indexOf(listener);

    if (listenerIndex !== -1) {
      this.listeners[eventName].splice(listenerIndex, 1);
    }

    if (this.listeners[eventName].length === 0) {
      delete this.listeners[eventName];
    }
  }
}

const eventManager = new EventManager();
export default eventManager;