sindresorhus

emittery

novemberborn

const anyProducer = Symbol('anyProducer');

const resolvedPromise = Promise.resolve();

const listenerAdded = Symbol('listenerAdded');

const listenerRemoved = Symbol('listenerRemoved');

	if (typeof eventName !== 'string' && typeof eventName !== 'symbol') {

		throw new TypeError('eventName must be a string or a symbol');

		throw new TypeError('listener must be a function');

function getListeners(instance, eventName) {

function getEventProducers(instance, eventName) {

	const key = typeof eventName === 'string' || typeof eventName === 'symbol' ? eventName : anyProducer;

	const producers = producersMap.get(instance);

function enqueueProducers(instance, eventName, eventData) {

		for (const producer of producers.get(eventName)) {

		const item = Promise.all([eventName, eventData]);

		for (const producer of producers.get(anyProducer)) {

function iterator(instance, eventNames) {

	eventNames = Array.isArray(eventNames) ? eventNames : [eventNames];

		getEventProducers(instance, eventName).add(producer);

			this.debug.logger = (type, debugName, eventName, eventData) => {

				eventData = JSON.stringify(eventData);

					// TODO: Use https://github.com/sindresorhus/safe-stringify when the package is more mature. Just copy-paste the code.

					eventData = JSON.stringify(eventData);

					eventData = `Object with the following keys failed to stringify: ${Object.keys(eventData).join(',')}`;

				const logTime = `${currentTime.getHours()}:${currentTime.getMinutes()}:${currentTime.getSeconds()}.${currentTime.getMilliseconds()}`;

				console.log(`[${logTime}][emittery:${type}][${debugName}] Event Name: ${eventName}\n\tdata: ${eventData}`);

	logIfDebugEnabled(type, eventName, eventData) {

		if (Emittery.isDebugEnabled || this.debug.enabled) {

			this.debug.logger(type, this.debug.name, eventName, eventData);

		eventNames = Array.isArray(eventNames) ? eventNames : [eventNames];

			getListeners(this, eventName).add(listener);

			this.logIfDebugEnabled('subscribe', eventName, undefined);

				this.emit(listenerAdded, {eventName, listener});

		return this.off.bind(this, eventNames, listener);

			getListeners(this, eventName).delete(listener);

			this.logIfDebugEnabled('unsubscribe', eventName, undefined);

				this.emit(listenerRemoved, {eventName, listener});

			const off = this.on(eventNames, data => {

		this.logIfDebugEnabled('emit', eventName, eventData);

		enqueueProducers(this, eventName, eventData);

		const listeners = getListeners(this, eventName);

		const staticListeners = [...listeners];

		const staticAnyListeners = isListenerSymbol(eventName) ? [] : [...anyListeners];

			...staticListeners.map(async listener => {

			...staticAnyListeners.map(async listener => {

					return listener(eventName, eventData);

	async emitSerial(eventName, eventData) {

		this.logIfDebugEnabled('emitSerial', eventName, eventData);

	"description": "Simple and modern async event emitter",

	"funding": "https://github.com/sindresorhus/emittery?sponsor=1",

# <img src="media/header.png" width="1000">

[![Coverage Status](https://codecov.io/gh/sindresorhus/emittery/branch/main/graph/badge.svg)](https://codecov.io/gh/sindresorhus/emittery)

[![](https://badgen.net/bundlephobia/minzip/emittery)](https://bundlephobia.com/result?p=emittery)

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

Emitting events asynchronously is important for production code where you want the least amount of synchronous operations. Since JavaScript is single-threaded, no other code can run while doing synchronous operations. For Node.js, that means it will block other requests, defeating the strength of the platform, which is scalability through async. In the browser, a synchronous operation could potentially cause lags and block user interaction.

emitter.emit('🦄', '🌈'); // Will trigger printing '🌈'

emitter.emit(myUnicorn, '🦋');  // Will trigger printing 'Unicorns love 🦋'

Emittery accepts strings and symbols as event names.

Symbol event names can be used to avoid name collisions when your classes are extended, especially for internal events.

Default: `true` if the `DEBUG` environment variable is set to `emittery` or `*`, otherwise `false`.

const emitter1 = new Emittery({debug: {name: 'myEmitter1'}});

const emitter2 = new Emittery({debug: {name: 'myEmitter2'}});

//=> [16:43:20.417][emittery:subscribe][myEmitter1] Event Name: test

//=> [16:43:20.417][emittery:subscribe][myEmitter2] Event Name: otherTest

Configure the debugging options for this instance.

Define a name for the instance of Emittery to use when outputting debug data.

const emitter = new Emittery({debug: {name: 'myEmitter'}});

//=> [16:43:20.417][emittery:subscribe][myEmitter] Event Name: test

Toggle debug logging just for this instance.

const emitter1 = new Emittery({debug: {name: 'emitter1', enabled: true}});

const emitter2 = new Emittery({debug: {name: 'emitter2'}});

//=> [16:43:20.417][emittery:subscribe][emitter1] Event Name: test

Type: `Function(string, string, EventName?, Record<string, any>?) => void`

(type, debugName, eventName, eventData) => {

	const logTime = `${currentTime.getHours()}:${currentTime.getMinutes()}:${currentTime.getSeconds()}.${currentTime.getMilliseconds()}`;

	console.log(`[${logTime}][emittery:${type}][${debugName}] Event Name: ${eventName}\n\tdata: ${eventData}`);

const myLogger = (type, debugName, eventName, eventData) => console.log(`[${type}]: ${eventName}`);

		{
		"name": "emittery",
		"version": "0.10.1",
		"version": "0.10.2",
		"description": "Simple and modern async event emitter",
		@@ -5,0 +5,0 @@ "license": "MIT",

		@@ -92,3 +92,3 @@ # <img src="media/header.png" width="1000">

		Type: `objcect`
		Type: `object`

		@@ -95,0 +95,0 @@ Configure the debugging options for this instance.

		@@ -219,3 +219,8 @@ 'use strict';
		this.debug.logger = (type, debugName, eventName, eventData) => {
		eventData = JSON.stringify(eventData);
		try {
		// TODO: Use https://github.com/sindresorhus/safe-stringify when the package is more mature. Just copy-paste the code.
		eventData = JSON.stringify(eventData);
		} catch {
		eventData = `Object with the following keys failed to stringify: ${Object.keys(eventData).join(',')}`;
		}

		@@ -222,0 +227,0 @@ if (typeof eventName === 'symbol') {

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