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promitto

Tiny promise library compatible with Promise/A+ and ES6

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

Installation

Node.js

npm install promitto --save

Browser

Via Bower package manager

bower install promitto --save

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

<script src="//rawgithub.com/h2non/promitto/master/promitto.js"></script>

Environments

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('http://www.google.com', function (err, res) {
    if (err) defer.reject(err)
    else defer.resolve(res)
  })
  return defer.promise
}
 
doAsyncJob().then(function (data) {
  console.log(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('http://www.google.com', function (err, res) {
    if (err) reject(err)
    else resolve(res)
  })
})
 
promise.then(function (data) {
  console.log(data)
}).catch(function (reason) {
  console.error('Error:', reason)
})

API

promitto(callback)

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) {
  console.log('Name:', pkg.name)
}).catch(function (reason) {
  console.error('Error:', reason)
})

promitto.defer()

Creates a Deferred object

promitto.Promise(task)

Creates a new Promise compatible with the ES6 promise interface

promitto.when(value)

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

promitto.reject(reason)

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

promitto.resolve(reason)

Creates a promise that is resolved with the specified reason

promitto.all([promises])

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

promitto.isPromise(value)

Return if a given value is a compatible promise

Deferred

resolve(value)

Resolves the derived promise with the value

reject(reason)

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

notify(reason)

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

promise

Expose the Promise object associated with this deferred

Promise

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(callback)

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

finally(callback)

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

notify(callback)

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)

Contributing

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

Development

Only node.js is required for development

Clone/fork this repository

$ git clone https://github.com/h2non/promitto.git && 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

License

MIT - Tomas Aparicio