YouTube.js/src/utils/EventEmitterLike.ts

// Polyfill CustomEvents on node
if (!Reflect.has(globalThis, 'CustomEvent')) {

  // See https://github.com/nodejs/node/issues/40678#issuecomment-1126944677
  class CustomEvent extends Event {
    #detail;

    constructor(type: string, options?: CustomEventInit<any[]>) {
      super(type, options);
      this.#detail = options?.detail ?? null;
    }

    get detail() {
      return this.#detail;
    }
  }

  Reflect.set(globalThis, 'CustomEvent', CustomEvent);
}

export default class EventEmitterLike extends EventTarget {
  #legacy_listeners = new Map<(...args: any[]) => void, EventListener>();
  constructor() {
    super();
  }
  emit(type: string, ...args: any[]) {
    const event = new CustomEvent(type, { detail: args });
    this.dispatchEvent(event);
  }
  on(type: string, listener: (...args: any[]) => void) {
    const wrapper: EventListener = (ev) => {
      if (ev instanceof CustomEvent) {
        listener(...ev.detail);
      } else {
        listener(ev);
      }
    };
    this.#legacy_listeners.set(listener, wrapper);
    this.addEventListener(type, wrapper);
  }
  once(type: string, listener: (...args: any[]) => void) {
    const wrapper: EventListener = (ev) => {
      if (ev instanceof CustomEvent) {
        listener(...ev.detail);
      } else {
        listener(ev);
      }
      this.off(type, listener);
    };
    this.#legacy_listeners.set(listener, wrapper);
    this.addEventListener(type, wrapper);
  }
  off(type: string, listener: (...args: any[]) => void) {
    const wrapper = this.#legacy_listeners.get(listener);
    if (wrapper) {
      this.removeEventListener(type, wrapper);
      this.#legacy_listeners.delete(listener);
    }
  }
}