Server Middleware

ELI5 — The Vibe Check

Server middleware is code that runs between receiving a request and sending a response. It's like TSA checkpoints at the airport — every request goes through them in order. Logging, authentication, CORS, compression — all middleware. They can modify the request, reject it, or pass it along.

Real Talk

Server middleware are functions that intercept and process HTTP requests and responses in a pipeline. Each middleware can inspect/modify the request, execute logic, and either pass control to the next middleware or short-circuit the chain by sending a response. They enable cross-cutting concerns like authentication, logging, and error handling.

Show Me The Code

// Express middleware
app.use((req, res, next) => {
  console.log(`${req.method} ${req.url}`);
  req.startTime = Date.now();
  next();
});

app.use(cors());
app.use(express.json());

When You'll Hear This

"Add auth middleware before the protected routes." / "The CORS middleware needs to run before everything else."