node package manager
Share your code. npm Orgs help your team discover, share, and reuse code. Create a free org »


promitto Build Status NPM version

promitto is a tiny Promise/Deferred library for JavaScript environments which helps you when dealing with async tasks in a pretty and clean way. It provides an elegant, standard and simple API

It's compatible with the Promise/A+ spec and provides useful features for asynchronous promise-based programming patterns

promitto is written in Wisp, a Clojure-like language which transpiles into plain JavaScript. It exploits functional programming common patterns such as lambda lifting, pure functions, higher-order functions, function composition and more



npm install promitto --save


Via Bower package manager

bower install promitto --save

Or loading the script remotely (just for testing or development)

<script src="//"></script>


It works properly in any ES5 compliant engine

  • Node.js
  • Chrome >= 5
  • Firefox >= 3
  • Safari >= 5
  • Opera >= 12
  • IE >= 9

Basic usage

var promitto = require('promitto')

Using Deferred pattern

var p = require('promitto')
function doAsyncJob() {
  var defer = p.defer()
  get('', function (err, res) {
    if (err) defer.reject(err)
    else defer.resolve(res)
  return defer.promise
doAsyncJob().then(function (data) {
}).catch(function (reason) {
  console.error('Error:', reason)

Using Promise pattern (Promise/A+ / ES6 compatible)

var Promise = require('promitto').Promise
var promise = Promise(function doJob(resolve, reject, notify) {
  get('', function (err, res) {
    if (err) reject(err)
    else resolve(res)
promise.then(function (data) {
}).catch(function (reason) {
  console.error('Error:', reason)



Create a new promitto promise passing a function task

promitto(function readPackage(resolve, reject, notify) {
  fs.readFile('./package.json', function (err, data) {
    if (err) reject(err)
    else resolve(JSON.parse(data))
}).then(function (pkg) {
}).catch(function (reason) {
  console.error('Error:', reason)


Creates a Deferred object


Creates a new Promise compatible with the ES6 promise interface


Wrap an object that might be a value or a 3rd party promise

This is useful when you are dealing with an object that might or might not be a promise, or if the promise comes from a source that can't be trusted


Creates a promise that is resolved as rejected with the specified reason


Creates a promise that is resolved with the specified reason


Combines multiple promises into a single promise that is resolved when all of the input promises are resolved

Returns a single promise that will be resolved with an array/hash of values, each value corresponding to the promise at the same index/key in the promises array/hash


Return if a given value is a compatible promise



Resolves the derived promise with the value


Rejects the derived promise with the reason. This is equivalent to resolving it with a rejection constructed via promitto.reject


Provides updates on the status of the promise's execution. This may be called multiple times before the promise is either resolved or rejected


Expose the Promise object associated with this deferred


then(onResolve, onReject, onNotify)

Regardless of when the promise was or will be resolved or rejected, then calls one of the success or error callbacks asynchronously as soon as the result is available.

The callbacks are called with a single argument: the result or rejection reason. Additionally, the notify callback may be called zero or more times to provide a progress indication, before the promise is resolved or rejected


Catch promise resolve as reject status. Shorthand for promise.then(null, onReject)


Allows you to observe either the fulfillment or rejection of a promise, but to do so without modifying the final value. This is useful to release resources or do some clean-up that needs to be done whether the promise was rejected or resolved


Handle the promise progress while it's still on pending state. This is useful when you want to report the state of the process until it's finally fulfilled (resolved or rejected)


Wanna help? Cool! It will be appreciated :)

You must add new test cases for any new feature or refactor you do, always following the same design/code patterns that already exist

Tests specs are completely written in Wisp language. Take a look to the language documentation if you are new with it. You should follow the Wisp language coding conventions


Only node.js is required for development

Clone/fork this repository

$ git clone && cd promitto

Install package dependencies

$ npm install

Compile code

$ make compile

Run tests

$ make test

Browser sources bundle generation

$ make browser

Release a new version

$ make release


MIT - Tomas Aparicio