❤
npm
Sign UpSign In

async-for-of

1.0.1 • Public • Published

Promisified, asynchronous ES6 for..of

Installation

npm install async-for-of

Usage

async-for-of can loop asynchronously over any iterable, only requesting the item when "next" is called

var forOf = require('async-for-of')
 
forOf(iterable, (item, next, end) => { 
  //do something with item, then call next() or end(result)
}).then((result) => {
  //do something with the result
})

iterable is an array, generator, function or custom iterable of any type (typically Promises)

forOf returns a Promise that is fulfilled when:

  • end is called (with resolve with the value passed to that function)
  • the iterable returns done (will resolve with an undefined result)

Check out the tests to see expected behaviour.

Examples

Asynchronous Random Number Generator

This example asynchronously generates random numbers and resolves when the result matches certain criteria

var asyncRandomGenerator = () => {
  console.log('Generating value')
  return Promise.resolve(Math.random())
}
 
forOf(asyncRandomGenerator, (item, next, end) => {
  item.then(val => {
    console.log('Inspecting value')
    if (val < 0.1)
      end(val)
    else
      next()
  })
}).then(val => console.log('Success: ' + val))

Asynchronous Random Number Generator #2

This builds on the above example, using an ES6 generator to add some control flow - in this case, enforcing the maximum number of attempts

var asyncRandomGenerator = function*() {
  var maxAttempts = 5
  for (var i = 0; i < maxAttempts; i++) {
    console.log('Generating value')
    yield Promise.resolve(Math.random())
  }
  throw 'Max Attempts Exceeded'
}
 
forOf(asyncRandomGenerator(), (promise, next, end) => {
  promise.then(val => {
    console.log('Inspecting value')
    if (val < 0.1)
      end(val)
    else
      next()
    });
}).then(val => console.log('Success: ' + val))
.catch(err => console.log('Failure: ' + err))

Peer Discovery

This example finds an active peer from a list (ideally broadcasted) and resolves with a socket

var server = net.createServer();
server.listen(8002);
 
var peers = [
  { host: '127.0.0.1', port: 8000 },
  { host: '127.0.0.1', port: 8001 },
  { host: '127.0.0.1', port: 8002 }
]
 
forOf(peers, (peer, next, end) => {
  console.log('Attempting to connect to ' + JSON.stringify(peer))
 
  var socket = net.connect(peer.port, peer.host)
  socket.on('connect', () => end({ peer, socket }))
  socket.on('error', next)
}).then(result => {
  console.log('Peer found: ' + JSON.stringify(result.peer))
  
  //do something with result.socket
})

Readme

Keywords

Package Sidebar

Install

npm i async-for-of

Repository

github.com/tristanhoy/async-for-of

Homepage

github.com/tristanhoy/async-for-of#readme

Weekly Downloads

1

Version

1.0.1

License

ISC

Last publish

Collaborators

  • tristan.hoy
Try on RunKit
Report malware