Adds types to EventEmitter methods

EventBase.ts

import { EventEmitter } from 'events';

type EventTypes = Record<string | symbol, (...args: []) => void>;

/**
 * Adds types to the following methods of {@link EventEmitter}
 * * {@link EventEmitter.on}
 * * {@link EventEmitter.off}
 * * {@link EventEmitter.once}
 * * {@link EventEmitter.emit}
 * * {@link EventEmitter.removeAllListeners}
 * * {@link EventEmitter.eventNames}
 * * {@link EventEmitter.listenerCount}
 */
abstract class EventBase<T = EventTypes> extends EventEmitter {
  constructor() {
    super();
  }

  public on<E extends keyof T>(event: Extract<E, string | symbol>, listener: T[E] extends (...args: any[]) => void ? T[E] : never) {
    return super.on(event, listener);
  }

  public off<E extends keyof T>(event: Extract<E, string | symbol>, listener: T[E] extends (...args: any[]) => void ? T[E] : never) {
    return super.off(event, listener);
  }

  public once<E extends keyof T>(event: Extract<E, string | symbol>, listener: T[E] extends (...args: any[]) => void ? T[E] : never) {
    return super.once(event, listener);
  }

  public emit<E extends keyof T>(event: Extract<E, string | symbol>, ...args: T[E] extends (...args: any[]) => void ? Parameters<T[E]> : never) {
    return super.emit(event, args);
  }

  public removeAllListeners<E extends keyof T>(event?: Extract<E, string | symbol>) {
    return super.removeAllListeners(event);
  }

  public eventNames() {
    return super.eventNames();
  }

  public listenerCount<E extends keyof T>(event: Extract<E, string | symbol>) {
    return super.listenerCount(event);
  }
}

export default EventBase;