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    8.2.3 • Public • Published

    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=""></script>


    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


    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) {};


    npm install
    npm test




    npm i promise-polyfill

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    Unpacked Size

    49 kB

    Total Files


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    • taylorhakes