Started here - https://github.com/facebookincubator/create-react-app/pull/1433#discussion_r104329257 (only for packages/react-scripts) * If arrow functions are already used maybe switch others functions to arrow ? * Same for `var` -> `const`. For example: * [test.js](https://github.com/facebookincubator/create-react-app/blob/3fa5e8e7d7a1b0d004e51a39afc2aa074808aa2a/packages/react-scripts/scripts/test.js) - only `const` is used * [start.js](https://github.com/facebookincubator/create-react-app/blob/3fa5e8e7d7a1b0d004e51a39afc2aa074808aa2a/packages/react-scripts/scripts/start.js) - only `var` is used * [webpack.config.prod.js](https://github.com/facebookincubator/create-react-app/blob/3fa5e8e7d7a1b0d004e51a39afc2aa074808aa2a/packages/react-scripts/config/webpack.config.prod.js) both `var` and `const`are used