@esmj/emitter

Emitter

The @esmj/emitter is tiny (O,9kB) async event emitter library.

It works in Node.js and the browser (using a bundler like webpack).

Requirements

• Node 18+

Install

npm install @esmj/emitter

Usage

It works for both Javascript modules (ESM and CJS).

import { Emitter } from '@esmj/emitter';

const emitter = new Emitter();

emitter.on('some-event', async (event) => {
  return 2 * event.result;
});

emitter.on('some-event', (event) => {
  return 3 * event.result;
});

emitter.on('some-event', (event) => {
  event.stopPropagation();
});

emitter.on('some-event', async (event) => {
  return 4 * event.result;
});

const { result } = await emitter.emit('some-event', { result: 1 });

console.log(result); // 6

API

emitter = new Emitter(options?)

Create a new instance of Emitter.

options?

Type: object

Configure the new instance of Emitter.

logger?

Type: object Default: console

Configure the logger for this instance.

debug?

Type: boolean|function(eventName, event) Default: false

Configure the debugging options for this instance.

on(eventName, listener) / addListener(eventName, Listener)

Subscribe listener for event.

Returns an unsubscribe method.

off(eventName, listener) / removeListener(eventName, Listener)

Remove subscription.

once(eventName, listener)

Subscribe event for listener only once. It will be unsubscribed after the first call.

emit(eventName, data?)

Trigger an event asynchronously/synchronously. It is depends on returns value from listener. Listeners are called in the order they were added and executed serially.