A minimal React on Rails implementation of HMR with React Hot Loader 3, Redux, React Router 4, CSS modules and Webpack 2

• bundle install
• cd client && yarn
• foreman start
• visit localhost:3000 and change source code to check out HMR

• in package.json
  • add "react-hot-loader"
• in .babelrc
  • use es2015 preset, disable modules and add "react-hot-loader/babel" plugin
• in webpack.config.js
  • add "react-hot-loader/patch" right before your root source file (e.g. client/entry in this rep) in to "entry" config
  • add new webpack.HotModuleReplacementPlugin() to plugins config
  • add hot: true (or hotOnly: true), and headers: { "Access-Control-Allow-Origin": "http://yourRailsHost" } (or just headers: { "Access-Control-Allow-Origin": "*" }) to devServer config
• in your root source file (e.g. client/entry.js in this rep)
  • wrap your elements in AppContainer from react-hot-loader package
  • use module.hot.accept and specify modules and how they are going to be replaced

Check out the source code for more details.