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Vow NPM version Build Status

Vow is a Promises/A+ implementation. It also supports ES6 Promises specification.

Full API reference can be found at

Getting Started

In Node.js

You can install using Node Package Manager (npm):

npm install vow

In Browsers

<script type="text/javascript" src="vow.min.js"></script>

It also supports RequireJS module format and YM module format.

Vow has been tested in IE6+, Mozilla Firefox 3+, Chrome 5+, Safari 5+, Opera 10+.


Creating a promise

There are two possible ways to create a promise.

1. Using a deferred

function doSomethingAsync() {
    var deferred = vow.defer();
    // now you can resolve, reject, notify corresponging promise within `deferred`
    // e.g. `defer.resolve('ok');`
    return deferred.promise(); // and return corresponding promise to subscribe to reactions
    function() {}, // onFulfilled reaction
    function() {}, // onRejected reaction
    function() {}  // onNotified reaction

The difference between deferred and promise is that deferred contains methods to resolve, reject and notify corresponding promise, but the promise by itself allows only to subscribe on these actions.

2. ES6-compatible way

function doSomethingAsync() {
    return new vow.Promise(function(resolve, reject, notify) {
        // now you can resolve, reject, notify the promise
    function() {}, // onFulfilled reaction
    function() {}, // onRejected reaction
    function() {}  // onNotified reaction

Extensions and related projects

  • vow-fs — vow-based file I/O for Node.js
  • vow-node — extension for vow to work with nodejs-style callbacks
  • vow-queue — vow-based task queue with weights and priorities
  • vow-asker — wraps asker API in the vow promises implementation

NOTE. Documentation for old versions of the library can be found at