# events-async

> A wrapper around the EventEmitter to handle promise based async events

Latest version **1.2.1** (published 2020-02-18) · ISC license · 0 weekly downloads

## Install

```sh
npm install events-async
pnpm add events-async
yarn add events-async
bun add events-async
```

## Health

**Score 15/100 (F)** — status: abandoned.

Positive: no vulnerabilities.

Warnings: low downloads; no types; no esm support.

Negative: abandoned; low maintenance score.

## Facts

| | |
|---|---|
| Version | 1.2.1 |
| Published | 2020-02-18 |
| First published | 2016-03-07 |
| Weekly downloads | 0 |
| License | ISC |
| TypeScript types | none |
| Module format | CommonJS |
| Dependencies | 0 |
| Unpacked size | 15.3 KB |
| Known vulnerabilities | 0 |
| Install scripts | no |
| GitHub stars | 11 |
| Author | Wes Todd |
| Maintainers | rbayliss, tjbenton21, wesleytodd |
| Keywords | events, EventEmitter, async, promise |

## Links

- npm: https://www.npmjs.com/package/events-async
- Repository: https://github.com/wesleytodd/events-async
- Issues: https://github.com/wesleytodd/events-async/issues
- npm.io page: https://npm.io/package/events-async

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## Recent versions

- 1.2.1 (latest) — 2020-02-18
- 1.2.0 — 2020-02-18
- 1.1.0 — 2017-02-06
- 1.0.0 — 2016-03-07

## README

# Events, but asynchronous

[![NPM Version][npm-image]][npm-url]
[![NPM Downloads][downloads-image]][downloads-url]
[![Build Status](https://travis-ci.org/wesleytodd/events-async.svg?branch=master)](https://travis-ci.org/wesleytodd/events-async)
[![js-happiness-style](https://img.shields.io/badge/code%20style-happiness-brightgreen.svg)](https://github.com/JedWatson/happiness)

[npm-image]: https://img.shields.io/npm/v/events-async.svg
[npm-url]: https://npmjs.org/package/events-async
[downloads-image]: https://img.shields.io/npm/dm/events-async.svg
[downloads-url]: https://npmjs.org/package/events-async

This module is the lightest wrapper I could come up with around the `EventEmitter` to add support for async events with Promises.  It only re-implements the `emit` method.  This now returns a `Promise` which will be resolved when all the event handlers have completed.

Handler functions can return a `Promise` to indicate that they are asynchronous which will then wait for resolution before emit resolves.

## Install

```
$ npm install --save events-async
```

## Usage

```javascript
var EventEmitter = require('events-async');

var ee = new EventEmitter();

// Add an asyncronous listener
ee.on('evt', function () {
	return new Promise(function (resolve, reject) {
		// Do something async, for example:
		process.nextTick(function () {
			resolve();
		});
	});
});

// Emit an event and wait for it to complete
ee.emit('evt').then(function () {
	// All of the listeners have run
});
```

With this module you can mix async listeners and sync listeners, so you are not tied to the promise interface when you don't need it.  Listeners that don't return a promise are just run in the normal sync fashion.

This module also supports the same argument passing behavior as node core's `EventEmitter`.  It is actually as close to a direct port for that as possible, including the performance optimizations.


By default handler functions are run in parallel. If you need to run them in a series the first argument of the emit function needs to be an object with the `series` option passed.


```javascript
var EventEmitter = require('events-async');
var delay = require('delay');
var actual = [];

var ee = new EventEmitter();

// first
ee.on('evt', function () {
	return delay(300).then(function () {
			actual.push(300);
		});
});

// second
ee.on('evt', function () {
	return delay(200).then(function () {
			actual.push(200);
		});
});

// third
ee.on('evt', function () {
	return delay(100).then(function () {
			actual.push(100);
		});
});

// Emit an event and wait for it to complete
ee.emit({ serial: true }, 'evt').then(function () {
	// All of the listeners have run
	console.log(actual);
	//=> [ 300, 200, 100 ]
});
```


If you want to catch an error instead of it throwing a hard error then pass `{ catch: true }` into the emit options.

---
_Source: https://npm.io/package/events-async · Machine-readable twin of the npm.io package page. Health data is recomputed on every publish._