Lightweight ES6 Promise polyfill for the browser and node. Adheres closely to the spec. It is a perfect polyfill IE, Firefox 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
Downloads
Simple use
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._setImmediateFn(immedateFn)
it will be used instead of window.setTimeout
npm install setasap --save
var Promise = require('promise-polyfill');
var setAsap = require('setasap');
Promise._setImmediateFn(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 turn off this behavior by setting Promise._setUnhandledRejectionFn(<rejectError>)
.
If you would like to disable unhandled rejections. Use a noop like below.
Promise._setUnhandledRejectionFn(function(rejectError) {});
Testing
npm install
npm test
License
MIT