How to turn on/off ReactJS 'development mode'?

Question

Started using ReactJS\'s prop validation feature, which as the docs say only works in \'development mode\' for performance reasons.

React seems to be validating the

Answer 1

If you're working from something like this ReactJS.NET / Webpack tutorial, you can't use process.env to switch React development mode on/off as far as I can tell. This sample links to react.js directly (see Index.cshtml), so you just have to pick .min.js or the non-minified variant by changing the URL.

I'm not sure why that is the case, because the sample's webpack.config.js has a comment that seems to imply the externals: { react: 'React' } would do the job, but then goes ahead and includes react directly into the page.