Promise Polyfill
Lightweight ES6 Promise polyfill for the browser and node. Adheres closely to
the spec. It is a perfect polyfill IE or any other browser that does
not support native promises.
For API information about Promises, please check out this article
HTML5Rocks article.
It is extremely lightweight. < 1kb Gzipped
Browser Support
IE8+, Chrome, Firefox, IOS 4+, Safari 5+, Opera
NPM Use
npm install promise-polyfill --save-exact
Bower Use
bower install promise-polyfill
CDN Polyfill Use
This will set a global Promise object if the browser doesn't already have window.Promise.
<script src="https://cdn.jsdelivr.net/npm/promise-polyfill@8/dist/polyfill.min.js"></script>
Downloads
Simple use
If you would like to add a global Promise object (Node or Browser) if native Promise doesn't exist (polyfill Promise). Use the method below. This is useful if you are building a website and want to support older browsers.
Javascript library authors should NOT use this method.
import 'promise-polyfill/src/polyfill';
If you would like to not affect the global environment (sometimes known as a ponyfill, you can import the base module. This is nice for library authors or people working in environment where you don't want
to affect the global environment.
import Promise from 'promise-polyfill';
If using require with Webpack 2+ (rare), you need to specify the default import
var Promise = require('promise-polyfill').default;
then you can use like normal Promises
var prom = new Promise(function(resolve, reject) {
// do a thing, possibly async, then…
if (/* everything turned out fine */) {
resolve("Stuff worked!");
} else {
reject(new Error("It broke"));
}
});
prom.then(function(result) {
// Do something when async done
});
Performance
By default promise-polyfill uses setImmediate, but falls back to setTimeout
for executing asynchronously. If a browser does not support setImmediate
(IE/Edge are the only browsers with setImmediate), you may see performance
issues. Use a setImmediate polyfill to fix this issue.
setAsap or
setImmediate work well.
If you polyfill window.setImmediate or use Promise._immediateFn = yourImmediateFn it will be used instead of window.setTimeout
npm install setasap --save
import Promise from 'promise-polyfill/src/polyfill';
import setAsap from 'setasap';
Promise._immediateFn = setAsap;
Unhandled Rejections
promise-polyfill will warn you about possibly unhandled rejections. It will show
a console warning if a Promise is rejected, but no .catch is used. You can
change this behavior by doing.
-NOTE: This only works on promise-polyfill Promises. Native Promises do not support this function
Promise._unhandledRejectionFn = <your reject error handler>;
If you would like to disable unhandled rejection messages. Use a noop like
below.
Promise._unhandledRejectionFn = function(rejectError) {};
Testing
npm install
npm test
License
MIT