I'm doing the fullstackopen course. There's a part where you create the production build files of a React application and copy them to the backend directory so that they can be served as static files. To optimize the task, they suggest adding this npm script to the backend directory:
"build:ui": "rm -rf build && cd ../../osa2/materiaali/notes-new && npm run build --prod && cp -r build ../../../osa3/notes-backend/",
If I understand correctly, this removes the build folder from the backend, then changes directory to the frontend where it creates a new production build and then copies the folder to the backend. But what is the --prod flag doing? I made a small test, running npm run buildand npm run build --prod and the output seems to be the same.