createEventListener

Event listeners are created via eventStore.createEventListener(name). They are the simplest way to react to events — ideal for stateless side effects like sending emails, invalidating caches, or logging.

Unlike projections and process managers, event listeners have no checkpoint tracking, no replay support, and no state. They fire for every event as it is emitted.

Creation

const listener = eventStore.createEventListener('notifications')

Builder Methods

.withEventHandlers(handlers)

Registers event handlers named on{EventName}.

listener.withEventHandlers({
  async onUserCreated({ payload }) {
    await sendWelcomeEmail(payload.email)
  },
})

.withGlobalEventHandler(handler)

Registers a catch-all handler called for every event.

listener.withGlobalEventHandler(async (event) => {
  console.log(`Event ${event.type} at position ${event.position}`)
})

.withAfterEffects(handlers)

Registers handlers that run after all on{EventName} handlers. Uses after{EventName} naming.

listener.withAfterEffects({
  async afterUserDeleted({ streamId }) {
    await invalidateCache(`user:${streamId}`)
  },
})

.withGlobalAfterEffect(handler)

A catch-all handler that runs after all after-effect handlers.

listener.withGlobalAfterEffect(async (event) => {
  await auditLog.append(event)
})

Context Helpers

import { isInsideEventListener, getEventListenerInfo } from '@requence/event-sourcing'

Function	Return Type	Description
isInsideEventListener()	boolean	true if called within an event listener handler.
getEventListenerInfo()	{ name, event } | undefined	Returns the listener name and triggering event.