EventEmitter

EventEmitter lets you emit named events and register listeners. It helps separate whoever sends an event from what reacts to it.

import { EventEmitter } from 'node:events';
const events = new EventEmitter();

events.on('orderCreated', order => {
  console.log('New order:', order.id);
});
events.emit('orderCreated', { id: 42 });

To be precise: listeners are called synchronously by default. emit doesn't wait for async listeners to finish.

In practice: an in-process event is fine, e.g. for locally observing an operation's lifecycle. It doesn't replace a durable queue with retries. The error event must be handled — without a handler it can crash the process.