Typed EventEmitter

typed-event-emitter.ts

import { EventEmitter } from 'events'

class TypedEventEmitter<TEvents extends Record<string, any>> {
  private emitter = new EventEmitter()

  emit<TEventName extends keyof TEvents & string>(eventName: TEventName, ...eventArgs: TEvents[TEventName]) {
    this.emitter.emit(eventName, ...eventArgs)
  }

  on<TEventName extends keyof TEvents & string>(eventName: TEventName, handler: (...eventArgs: TEvents[TEventName]) => void) {
    this.emitter.on(eventName, handler as any)
  }

  off<TEventName extends keyof TEvents & string>(eventName: TEventName, handler: (...eventArgs: TEvents[TEventName]) => void) {
    this.emitter.off(eventName, handler as any)
  }
}


type EventTypes = {
  'event-1': []
  'event-2': [arg1: number, arg2: string]
}

export const EventBroker = new TypedEventEmitter<LocalEventTypes>()

EventBroker.on('event-1', () => {})
EventBroker.on('event-2', (arg1: number, arg2: string) => {})

EventBroker.emit('event-2', 4, 'test')
EventBroker.emit('event-1')