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https://github.com/sindresorhus/ponyfill
🦄 Like polyfill but with pony pureness
https://github.com/sindresorhus/ponyfill
polyfill ponies ponyfill unicorns
Last synced: 16 days ago
JSON representation
🦄 Like polyfill but with pony pureness
- Host: GitHub
- URL: https://github.com/sindresorhus/ponyfill
- Owner: sindresorhus
- Created: 2016-09-29T14:19:54.000Z (over 7 years ago)
- Default Branch: main
- Last Pushed: 2024-02-06T09:31:52.000Z (5 months ago)
- Last Synced: 2024-05-22T19:05:30.037Z (about 1 month ago)
- Topics: polyfill, ponies, ponyfill, unicorns
- Homepage:
- Size: 553 KB
- Stars: 1,200
- Watchers: 19
- Forks: 26
- Open Issues: 1
-
Metadata Files:
- Readme: readme.md
Lists
- awesome-stars - sindresorhus/ponyfill - 🦄 Like polyfill but with pony pureness (Others)
- awesome-stars - sindresorhus/ponyfill - 🦄 Like polyfill but with pony pureness (Others)
- my-awesome-stars - sindresorhus/ponyfill - 🦄 Like polyfill but with pony pureness (Others)
README
Like polyfill but with pony pureness
*Use [ponyfill.com](https://ponyfill.com) for linking here.*
## Pony pureness, really?
While polyfills are naughty, ponyfills are pure, just like ponies.
## How are ponyfills better than polyfills?
A [polyfill](https://en.wikipedia.org/wiki/Polyfill_(programming)) is code that adds missing functionality by [monkey patching](https://en.wikipedia.org/wiki/Monkey_patch) an API. Unfortunately, it usually globally patches built-ins, which affects all code running in the environment. This is especially problematic when a polyfill is not fully spec compliant (which in some cases is impossible), as it could cause very hard to debug bugs and inconsistencies. Or when the spec for a new feature changes and your code depends on behavior that a module somewhere else in the dependency tree polyfills differently. In general, [you should not modify API's you don't own.](https://www.nczonline.net/blog/2010/03/02/maintainable-javascript-dont-modify-objects-you-down-own/)
A ponyfill, in contrast, doesn't monkey patch anything, but instead exports the functionality as a normal module, so you can use it locally without affecting other code.
*tl;dr:* Polyfills are naughty as they patch native APIs, while ponyfills are pure and don't affect the environment.
### Polyfill
```js
Number.isNaN ??= function (value) {
return value !== value;
};
```
```js
import 'is-nan-polyfill';
Number.isNaN(5);
```
### Ponyfill
```js
export default function isNaN(value) {
return value !== value;
};
```
```js
import isNanPonyfill from 'is-nan-ponyfill';
isNanPonyfill(5);
```
**Ponyfills should avoid using native APIs**, because potential bugs or differences in the native APIs will make such a ponyfill less robust (therefore defeating one of its main purposes). There are important exceptions, such as when:
- There is no way to implement some of the ponyfill without native APIs.
- Reimplementing native parts would have a large cost (e.g. performance or code size).
In such cases, it's still valuable for the ponyfill to minimize any assumptions about the underlying environment.
## Where can I find ponyfills?
[Search npm.](https://npms.io/search?q=keywords%3Aponyfill)
## How do I make a ponyfill?
- Read the specification or source code of the feature you want to ponyfill.
- Initialize an [npm package](https://github.com/sindresorhus/generator-nm).
- [Write some tests](https://avajs.dev) to ease writing the ponyfill logic.
- Link to documentation about the feature in your readme. [Example.](https://github.com/sindresorhus/buffer-includes#readme)
- Link to `https://ponyfill.com` in your readme. [Example.](https://github.com/sindresorhus/object-assign#readme)
- Add `ponyfill` to the `keywords` section in package.json.
- Publish!
## Resources
- [Ponyfill definition - Silicon Valley Dictionary](http://svdictionary.com/words/ponyfill)
- [Polyfills or Ponyfills? - Pony Foo](https://ponyfoo.com/articles/polyfills-or-ponyfills)
- [Polyfill, Ponyfill and Prollyfill - Kikobeats](https://kikobeats.com/polyfill-ponyfill-and-prollyfill/)
## License
[](https://creativecommons.org/publicdomain/zero/1.0/)
To the extent possible under law, [Sindre Sorhus](https://sindresorhus.com) has waived all copyright and related or neighboring rights to this work.
Header based on work by [Mary Winkler](https://www.vecteezy.com/members/acrylicana).