queue-event-emitter/README.md

Simple `EventEmitter` which runs every event handler in a queue

# queue-event-emitter

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`QueueEventEmitter` is a simple `EventEmitter` which runs every event handler in a queue.

## Installation

```bash
npm i --save queue-event-emitter
```

## Usage

```js
const QueueEventEmitter = require('queue-event-emitter')

// helper function
const sleep = (time) => (
  new Promise((resolve) => setTimeout(resolve, time))
)

// event emitter
const emitter = new QueueEventEmitter()

// event handlers, should return promise
emitter.on('first', async (data) => {
  await sleep(3000)
  console.log('data:', data)
})
emitter.on('second', async (data) => {
  await sleep(1000)
  console.log('data:', data)
})
emitter.on('third', async (data) => {
  await sleep(10)
  console.log('data:', data)
})

// send events
emitter.emit('first', 10)
emitter.emit('second', 20)
emitter.emit('third', 30)
emitter.emit('first', 40)
emitter.emit('third', 50)
emitter.emit('third', 60)
emitter.emit('second', 70)

// result in console will be
// data: 10
// data: 20
// data: 30
// data: 40
// data: 50
// data: 60
// data: 70
```

## API

Implements the same api as node's [EventEmitter](https://nodejs.org/api/events.html).

## Options

`QueueEventEmitter` class accepts following options:
 - `options.concurrency` `<number>` The maximum number of events to execute at once. (__Default:__ 1)

## Licence

Licensed under [MIT](LICENSE)