await-event-emitter/README.md

Await events library like EventEmitter

# await-event-emitter

Await events library like EventEmitter

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## Why?

The concept of Webpack plugin has lots of lifecycle hooks, they implement this via EventEmitter.
In the primitive [events](https://nodejs.org/dist/latest/docs/api/events.html) module on nodejs, the usage as follows

```javascript
const EventEmitter = require('events')
const emitter = new EventEmitter()

emitter
  .on('event', () => {
    // do something *synchronously*
  })
  .emit('event', '...arguments')
```

The listener must be **synchronous**, that is way i wrote it.  
And await-event-emitter support synchronous emitter magically :smile:

## Installation

```bash
npm install --save await-event-emitter
```

## Usage

```javascript
const AwaitEventEmitter = require('await-event-emitter').default

const emitter = new AwaitEventEmitter()
const tick = () =>
  new Promise((resolve) => {
    setTimeout(() => {
      console.log('tick')
      resolve()
    }, 1000)
  })

emitter.on('event', async () => {
  // wait to print
  await tick()
})

async function run() {
  // NOTE: it's important to `await` the reset process
  await emitter.emit('event', '...arguments')
  await emitter.emit('event', 'again')

  // support emit it synchronously
  emitter.emitSync('event', 'again')
}

run()
```

## API

### Class `AwaitEventEmitter`

- `addListener(event, listener)` : AwaitEventEmitter  
  alias: `on`
- `once(event, listener)`
- `prependListener(event, listener)` : AwaitEventEmitter  
  alias: `prepend`
- `prependOnceListener(event, listener)` : AwaitEventEmitter  
  alias: `prependOnce`
- `removeListener(event, listener)` : AwaitEventEmitter  
  alias: `off`
- `listeners(event)` : []
- `emit(event, ...args)` : Promise.resolve(boolean)  
  emit listeners asynchronously, we recommended await it resolved the result
- `emitSync(event, ...args)` : boolean
  emit listeners synchronously

## Test

```bash
npm test
```

## Contributing

- Fork it!
- Create your new branch:  
  `git checkout -b feature-new` or `git checkout -b fix-which-bug`
- Start your magic work now
- Make sure npm test passes
- Commit your changes:  
  `git commit -am 'feat: some description (close #123)'` or `git commit -am 'fix: some description (fix #123)'`
- Push to the branch: `git push`
- Submit a pull request :)

## Authors

This library is written and maintained by imcuttle, <a href="mailto:imcuttle@163.com">imcuttle@163.com</a>.

## License

MIT - [imcuttle](https://github.com/imcuttle) 🐟