For example, the React team provide a set of codemods to help automatically upgrade codebases when there is a new version of React (https://github.com/reactjs/r

For example, the React team provide a set of codemods to help automatically upgrade codebases when there is a new version of React (https://github.com/reactjs/react-codemod https://github.com/reactjs/react-codemod). Until `recast` gets TypeScript support, everybody who uses TypeScript has to do this repetitive work manually. Another example is how many `css-in-js` libraries require Babel plugins to work their best (e.g. https://github.com/emotion-js/emotion/tree/master/packages/babel-plugin-emotion https://github.com/emotion-js/emotion/tree/master/packages/b...). And additionally there are also plugins that optimize React code (e.g. https://github.com/thejameskyle/babel-react-optimize https://github.com/thejameskyle/babel-react-optimize).