Start with the Babel core Contributing docs.
Fork the babel-polyfills
repository to your GitHub Account.
Then, run:
$ git clone https://github.com/<your-github-username>/babel-polyfills
$ cd babel-polyfills
$ yarn
Then you can either run:
$ yarn build
to build the repo once or:
$ yarn watch
to have the repo build itself and incrementally build files on change.
$ yarn lint
$ yarn tscheck
$ yarn test