Why add app.use(express.json())?
To read JSON request bodies. Without it, req.body is undefined for JSON POST requests. Add it before your routes.
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More FAQs in How to Create an Express Server From Scratch
Run npm init -y, install express and nodemon, create server.js with app.get for health, add express.json(), cors if cross-origin, dotenv for env vars, and an error handler. Run with npm run dev and visit /health to confirm.
It restarts the server automatically when files change. Without it, you would have to stop and start the server manually every time you save a file. Add it as a dev dependency and use it in your dev script.
In an environment variable. Use dotenv to load a .env file with PORT=3000. In code, read process.env.PORT || 3000. Never hardcode configuration values.
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