MicroEmitter

A small, dependency-free event emitter for TypeScript and JavaScript.

Installation

npm install micro-emitter

MicroEmitter supports Node.js 22 and later.

Usage

import MicroEmitter from 'micro-emitter';

const emitter = new MicroEmitter();

emitter.on('change', (payload) => {
  console.log(payload);
});

emitter.emit('change', { message: 'Hello MicroEmitter!' });

CommonJS is also supported:

const MicroEmitter = require('micro-emitter');

API

All methods return the emitter so calls can be chained.

addListener(eventType, listener) / on(eventType, listener)

Registers a listener for an event. Registering the same function more than once creates multiple registrations.

addOnceListener(eventType, listener) / once(eventType, listener)

Registers a listener that is removed before its first invocation. Removing it first keeps recursive emissions from invoking it again.

removeListener(eventType, listener?) / off(eventType, listener?)

Removes all registrations of listener for the event. If listener is omitted, removes every listener for the event.

emit(eventType, payload?) / trigger(eventType, payload?)

Invokes the listeners registered when emission starts, in registration order. The listener receives payload, and its this value is the emitter.

Development

Use Node.js 22 or later and the npm version declared in packageManager.

npm ci
npm run check

npm run check verifies formatting, linting, types, tests, and the distributable build. The same command runs automatically before npm pack and npm publish.