event-promise

A respository for npm lt-event-promise

Same as node module events.EventEmitter but return Promise of executing listeners when call emit()

Installing

Using npm

``console
npm i lt-event-promise
`

With node
`js
const EventPromise = require('lt-event-promise')
const emitter = new EventPromise()
`

With client using webpack
`js
import EventPromise from 'lt-event-promise'
const emitter = new EventPromise()
`

Basic usage

`js

emitter.on('hello', () => console.log('Hello world!'))
emitter.emit('hello')

`

`console
Hello world!
`

Using Promise and async/await

###### Using Promise

`js
emitter.on('task', longTask)
emitter.emit('task')
.then(console.log)

function longTask() {
return new Promise(resolve => {
setTimeout(() => resolve('data'), 2000)
})
}
`

`console
[ 'data' ]
`

###### Many listeners

`js
emitter.on('task', task1, task2)
emitter.emit('task')
.then(console.log)

function task1() { return 'data1' }
function task2() { return 'data2' }
`

`console
[ 'data1', 'data2' ]
`

###### Error handling

`js
emitter.on('task', task, errorTask)
emitter.emit('task')
.then(console.log)
.catch(err => {
console.log('catch error here')
console.log(err)
})

function task() { return 'data' }
function errorTask() { throw new Error('Something went wrong!') }
`

`console
'catch error here'
...
throw new Error('Something went wrong!')
^
Error: Something went wrong!
...
`

###### Using async/await

`js
emitter.on('task', task1, task2)

try {
let datas = await emitter.emit('task')
console.log(datas)
} catch(err) {
console.error(err)
}
`
`console
[ 'data1', 'data2' ]
`

###### .on and .once

`js
emitter.on('task', onTask)
emitter.once('task', onceTask)

emitter.emit('task')
.then(datas => console.log('First emit:', datas))

emitter.emit('task')
.then(datas => console.log('Next emit:', datas))

function onTask() { return 'onData' }
function onceTask() { return 'onceData' }
`

`console
First emit: [ 'onData', 'onceData' ]
Next emit: [ 'onData' ]
``

License

MIT