While working on yet another React project using react-router, I discovered ±3kb of minified warning messages / development aids in my JavaScript bundle.

As it turns out, React’s practice of having different code for “development mode” and “production” is being used by other projects from community members, but not with the same level of caution – for this tooling to work, the build steps need to use specific configuration: https://facebook.github.io/react/docs/package-management.html.

Not all projects mention this, and more importantly not all projects warn you if you don’t. The solution? Configure your build step to remove those development aids in the entire bundle, and not just your own code.

More info at https://github.com/thibaudcolas/react-router-browserify-build/.

Other related links for future reference:

• https://github.com/ReactJSTraining/history/pull/307
• https://github.com/reactjs/react-router/pull/3503
• http://stackoverflow.com/questions/22118915/how-to-turn-on-off-reactjs-development-mode
• http://dev.topheman.com/make-your-react-production-minified-version-with-webpack/