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emittery

2.1.0194M downloads/mosindresorhus/emittery ↗New releases in your daily digest, changelog included.

Simple and modern async event emitter

Last release 8 days ago
26 Sep 2026
Release timing varies
gaps range from 2 weeks to 1.2 years
Most releases are documented
notes for 28 of 35 stable releases
Nothing withdrawn
no release was ever pulled
9 years old
35 releases · first in 2017

Release timeline

35 releases since 2017

20172019202120232025

Releases

2.1.026 Sept 2026
Improve TypeScript types cf2297d
Improvements

Improve TypeScript types cf2297d

Emittery.mixin() now returns a class type that includes the emittery property and the mixed-in methods

The iterators from .events() and .anyEvent() now type next() and return() precisely, instead of any

Emittery.listenerAdded and Emittery.listenerRemoved are now accepted everywhere the runtime accepts them, like .on(), .events(), and .listenerCount()

.emit() without data now works on an untyped emitter

.bindMethods() now accepts any object, including a class instance

methodNames for Emittery.mixin() and .bindMethods() now only accepts real method names. A list typed as string[] needs as const or the new EmitteryMethodName type.

Fixes

Fix async iterators hanging forever when next() is called concurrently 7157da9

Fix a rejected event data promise causing an unhandled rejection when an iterator never reads it 7157da9

A rejection that is read now throws from the iteration and closes the iterator, so a for await loop cannot leave the subscription behind.

Fix .clearListeners() with one event name ending an .events() iterator that listens to several events 7157da9

Fix .anyEvent() yielding the internal listenerAdded and listenerRemoved events 7157da9

Fix listenerAdded and listenerRemoved firing when nothing changed 4987e5f

For example, for a duplicate .on(), a repeated .off(), or .off() of a listener that was never added.

Fix .off() with several event names stopping at the first error and leaving the rest subscribed 4987e5f

Fix .offAny() not removing the listener when the debug logger throws 4987e5f

Fix the unsubscribe function from .on() changing when the event name array is mutated afterwards 4987e5f

Fix .clearListeners() removing every listener when given an invalid event name 51d4812

It now throws a TypeError. Only undefined means "all events".

Fix instances created from the same debug options object sharing their debug settings 5b47694

The options are now copied. To toggle logging after construction, set emitter.debug.enabled instead of changing the object you passed in.

Fix .emit() in environments without iterator helpers 4de0d10

Fix Emittery.mixin() silently overwriting an existing property with the same name as the emittery property 3702d31

v2.0.0...v2.1.0

One column per quarter.

2.0.04 Mar 2026

Listeners now receive a unified {name, data} object instead of raw data

Breaking Changes

Listeners now receive a unified `{name, data}` object instead of raw data

All listeners (.on(), .onAny(), .once(), async iterators) now receive a single event object with name and data properties instead of the raw event data.

- emitter.on('🦄', data => {
-   console.log(data);
+ emitter.on('🦄', ({data}) => {
+   console.log(data);
  });

For .onAny():

- emitter.onAny((eventName, eventData) => {
-   console.log(eventName, eventData);
+ emitter.onAny(({name, data}) => {
+   console.log(name, data);
  });

For .once():

- const data = await emitter.once('🦄');
+ const {data} = await emitter.once('🦄');

For .events() and .anyEvent() async iterators:

- for await (const data of emitter.events('🦄')) {
+ for await (const {data} of emitter.events('🦄')) {
    console.log(data);
  }

- for await (const [eventName, eventData] of emitter.anyEvent()) {
+ for await (const {name, data} of emitter.anyEvent()) {
    …
  }

For predicates in .once():

- emitter.once('data', data => data.ok === true);
+ emitter.once('data', ({data}) => data.ok === true);

`emit()` now throws `AggregateError` instead of rejecting with a single error

When multiple listeners throw, emit() now collects all errors into an AggregateError instead of silently dropping errors after the first one. All listeners always run to completion.

  try {
    await emitter.emit('event');
  } catch (error) {
-   // error was from the first listener that threw
+   // error is an AggregateError with all listener errors in error.errors
+   console.log(error.errors);
  }

Requires Node.js 22

The minimum required Node.js version is now 22 (previously 14.16).

New Features

init/deinit lifecycle hooks - Register setup/teardown logic that runs when the first listener subscribes and the last listener unsubscribes for a given event.
Disposable support - Unsubscribe functions from .on() and .onAny() are now Disposable (usable with using for automatic cleanup).
AsyncDisposable support - Async iterators from .events() and .anyEvent() are now AsyncDisposable (usable with await using).
AbortSignal support for .events(), .anyEvent(), and .once() - Pass {signal} to cancel subscriptions externally.
.once() options object - Accepts {predicate, signal} in addition to a plain predicate function.
TC39 standard decorator support - Emittery.mixin() now works with both legacy and TC39 standard decorator syntax.

Bug Fixes

emit() no longer silently drops errors from multiple listeners
Debug logger no longer emits noise for internal meta events
Fixed emitMetaEvent breaking async emit() overrides in subclasses
Fixed Emittery not working when wrapped in a Proxy
Fixed mixin decorator to work with TC39 standard decorator syntax

emittery

Release timeline

Releases

Improvements

Fixes

Breaking Changes

Listeners now receive a unified {name, data} object instead of raw data

emit() now throws AggregateError instead of rejecting with a single error

Requires Node.js 22

New Features

Bug Fixes

Breaking

Breaking for TypeScript users

Breaking

Improvements

Breaking

Improvements

Breaking

Improvements

Breaking

Enhancements

Listeners now receive a unified `{name, data}` object instead of raw data

`emit()` now throws `AggregateError` instead of rejecting with a single error