react-app-polyfill vs babel-polyfill

Hi,

I'm upgrading to react-script 2.1.1 from 1.x.x. Part of the instructions say that react-scripts doesn't support IE11 by default anymore, and recommends including react-app-polyfill to cover the gaps. However, I've already got import 'babel-polyfill; as the very first line of my entire React application, and have been able to run in IE11 to this point without major issue (to be clear, that's running with react-script 1.x.x).

So the question: what is the difference between react-app-polyfill and babel-polyfill? Is the former a subset of the latter? A superset? If babel-polyfill works for me, should I continue to use it, or switch over?

Thanks!

[thomasleduc]

Hi @bmueller-sykes,

Babel-polyfill comes with a massive amount of features that can be heavy for your application while react-app-polyfill comes only with 5 features :

1. Promise (for async / await support)
2. window.fetch (a Promise-based way to make web requests in the browser)
3. Object.assign (a helper required for Object Spread, i.e. { ...a, ...b })
4. Symbol (a built-in object used by for...of syntax and friends)
5. Array.from (a built-in static method used by array spread, i.e. [...arr])

If you use others features, you should keep babel-polyfill, else you should require in your src/index.js
import 'react-app-polyfill/ie11';

But I agree to say that it should appears in README.md with an explanation of what it is and why and when use it, the "how" being in the react-app-polyfill/README.md

Hope it helps.

Thanks!

Yeah, I use a few other things aside from those 5. In addition to babel-polyfill and react-app-polyfill, there's also core-js, which is a library of single polyfills, and is in fact what both babel-polyfill and react-app-polyfill use under the hood. So, one could in theory use react-app-polyfill for the bare minimum, and then just use whatever polyfills a specific app needs from core-js.

But yeah, having that info in the readme would be pretty nice.

[iansu]

Please send a PR updating the docs if you can.