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136 lines
3.6 KiB
Markdown
136 lines
3.6 KiB
Markdown
# Promise Polyfill
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[![travis][travis-image]][travis-url]
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[travis-image]: https://img.shields.io/travis/taylorhakes/promise-polyfill.svg?style=flat
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[travis-url]: https://travis-ci.org/taylorhakes/promise-polyfill
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Lightweight ES6 Promise polyfill for the browser and node. Adheres closely to
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the spec. It is a perfect polyfill IE or any other browser that does
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not support native promises.
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For API information about Promises, please check out this article
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[HTML5Rocks article](http://www.html5rocks.com/en/tutorials/es6/promises/).
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It is extremely lightweight. **_< 1kb Gzipped_**
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## Browser Support
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IE8+, Chrome, Firefox, IOS 4+, Safari 5+, Opera
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### NPM Use
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```
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npm install promise-polyfill --save-exact
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```
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### Bower Use
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```
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bower install promise-polyfill
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```
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### CDN Polyfill Use
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This will set a global Promise object if the browser doesn't already have `window.Promise`.
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```html
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<script src="https://cdn.jsdelivr.net/npm/promise-polyfill@8/dist/polyfill.min.js"></script>
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```
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## Downloads
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* [Promise](https://raw.github.com/taylorhakes/promise-polyfill/master/dist/polyfill.js)
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* [Promise-min](https://raw.github.com/taylorhakes/promise-polyfill/master/dist/polyfill.min.js)
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## Simple use
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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 it you are building a website and want to support older browsers.
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Javascript library authors should _NOT_ use this method.
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```js
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import 'promise-polyfill/src/polyfill';
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```
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If you would like to not affect the global environment (sometimes known as a [ponyfill](https://github.com/sindresorhus/ponyfill), you can import the base module. This is nice for library authors or people working in environment where you don't want
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to affect the global environment.
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```js
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import Promise from 'promise-polyfill';
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```
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If using `require` with Webpack 2+ (rare), you need to specify the default import
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```js
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var Promise = require('promise-polyfill').default;
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```
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then you can use like normal Promises
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```js
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var prom = new Promise(function(resolve, reject) {
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// do a thing, possibly async, then…
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if (/* everything turned out fine */) {
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resolve("Stuff worked!");
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} else {
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reject(new Error("It broke"));
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}
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});
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prom.then(function(result) {
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// Do something when async done
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});
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```
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## Performance
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By default promise-polyfill uses `setImmediate`, but falls back to `setTimeout`
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for executing asynchronously. If a browser does not support `setImmediate`
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(IE/Edge are the only browsers with setImmediate), you may see performance
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issues. Use a `setImmediate` polyfill to fix this issue.
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[setAsap](https://github.com/taylorhakes/setAsap) or
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[setImmediate](https://github.com/YuzuJS/setImmediate) work well.
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If you polyfill `window.setImmediate` or use `Promise._immediateFn = yourImmediateFn` it will be used instead of `window.setTimeout`
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```
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npm install setasap --save
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```
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```js
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import Promise from 'promise-polyfill/src/polyfill';
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import setAsap from 'setasap';
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Promise._immediateFn = setAsap;
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```
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## Unhandled Rejections
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promise-polyfill will warn you about possibly unhandled rejections. It will show
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a console warning if a Promise is rejected, but no `.catch` is used. You can
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change this behavior by doing.
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-**NOTE: This only works on promise-polyfill Promises. Native Promises do not support this function**
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```js
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Promise._unhandledRejectionFn = <your reject error handler>;
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```
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If you would like to disable unhandled rejection messages. Use a noop like
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below.
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```js
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Promise._unhandledRejectionFn = function(rejectError) {};
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```
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## Testing
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```
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npm install
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npm test
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```
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## License
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MIT
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