Reactjs:How to hide node modules and webconfig in the devtools on production app?

You see your full code in devtools because of source mapped files. It is a great way to debug your code in development or even for some people in production mode.

Without sourced maps, when an error occurs you can't easily find where this error is coming from in your bundled files. If you don't want to see your code like this in production you can simply delete the files after the built. Remove the .map files in your static/css and static/js folders. So, with this you can hide your unbundled source code. But, bundled .js and .css files will be always there. There is no way to hide them since this is frontend.

As told in the comments if your concern is really a security issue, then you can't do this on frontend. Your code always will be seen, at least its minified and uglified but there will be. So, do your security stuff in backend.

GENERATE_SOURCEMAP=false react-scripts build

this will not generate sourcemap (.map) files in the final build.