The files are located in your node_modules/react-scripts
folder:
Webpack config:
Start Script:
https://github.com/facebook/create-react-app/blob/master/packages/react-scripts/scripts/start.js
Build Script:
https://github.com/facebook/create-react-app/blob/master/packages/react-scripts/scripts/build.js
Test Script:
https://github.com/facebook/create-react-app/blob/master/packages/react-scripts/scripts/test.js
and so on ...
Now, the purpose of CRA is not to worry about these.
From the documentation:
You don’t need to install or configure tools like Webpack or Babel. They are preconfigured and hidden so that you can focus on the code.
If you want to have access to the config files, you need to eject by running:
npm run eject
Note: this is a one-way operation. Once you eject, you can’t go back!
In most scenarios, it is best not to eject and try to find a way to make it work for you in another way.
If you need to override some of the config options, you can have a look at https://github.com/gsoft-inc/craco