This is a Symfony 3 project w/ React JS in standalone mode and w/ WebSocket. 0.) Must installed modules w/ npm are in package.json + to global: $ npm install webpack -g You will need a .babelrc file w/ the presets webpack.config.js - https://webpack.github.io/docs/webpack-for-browserify-users.html same as dir where the package.json!! (!) Tutorial: https://egghead.io/lessons/react-introduction-to-properties 1.) Backend WebSocket server start as daemon - GeniusesOfSymfony/WebSocketBundle $ nohup bin/console gos:websocket:server & 2.) React JS WebPack watch generator w/ babel presets: es2015, react $ webpack -p --config=webpack-prod.config.js PROD $ webpack --progress --colors --watch -d DEV -d --> Debugger; If you write this line somewhere: debugger; The browser will stop the code here!!!