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ES6 Promise polyfill

This is a polyfill of ES6 Promise. The implementation based on Jake Archibald implementation a subset of rsvp.js. If you're wanting extra features and more debugging options, check out the full library.

For API details and how to use promises, see the JavaScript Promises HTML5Rocks article.


The main target: implementation should be conformance with browser's implementations and to be minimal as possible in size. So it's strictly polyfill of ES6 Promise specification and nothing more.

It passes both Promises/A+ test suite and rsvp.js test suite. And as small as 2,6KB min (or 1KB min+gzip).

The polyfill uses setImmediate if available, or fallback to use setTimeout. Use setImmediate polyfill by @YuzuJS to reach better performance.

How to use


To install:

bower install es6-promise-polyfill

To use:

<script src="bower_components/es6-promise-polyfill/promise.min.js"></script>
  var promise = new Promise(...);


To install:

npm install es6-promise-polyfill

To use:

var Promise = require('es6-promise-polyfill').Promise;
var promise = new Promise(...);


To install:

npm install es6-promise-polyfill

To use:

define(['es6-promise-polyfill'], function(Promise) {
  var promise = new Promise(...);

Usage in IE<9

catch is a reserved word in IE<9, meaning promise.catch(func) throws a syntax error. To work around this, use a string to access the property:

promise['catch'](function(err) {
  // ...

Or use .then instead:

promise.then(undefined, function(err) {
  // ...


Licensed under the MIT License.