Types of Middleware
PAANCH types hain: application-level (app.use), router-level (router.use), built-in (express.json, express.static, express.urlencoded), third-party (morgan, cors, helmet), aur error-handling (chaar arguments waale).
Built-in middleware Express ke saath aata hai — pehle body-parser jaisa alag package chahiye tha, Express 4.16+ se express.json() framework mein hi shaamil hai. Third-party middleware npm se aata hai aur usually app.use() se mount hota hai.
app.use(express.json()); // built-in
app.use(require("morgan")("dev")); // third-party
app.use("/api", apiRouter); // router-level
app.use((err, req, res, next) => { // error-handling (4 args)
res.status(500).json({ error: err.message });
});- 5 types: application, router, built-in, third-party, error-handling
- express.json/urlencoded/static built-in hain, alag package nahi chahiye
- Error middleware ki pehchaan uske CHAAR arguments hain
Express ke saath teen built-in middleware aate hain: express.json() (JSON body parse), express.urlencoded() (HTML form data), aur express.static() (files serve karna). Express 4.16 se pehle inke liye body-parser package alag se install karna padta tha.
app.use(express.json({ limit: "1mb" }));
app.use(express.urlencoded({ extended: true }));
app.use(express.static("public"));Express ki asli taakat uska middleware ecosystem hai — morgan (logging), cors (cross-origin), helmet (security headers), compression (gzip), cookie-parser (cookies), multer (file upload), express-rate-limit (throttling). Sab ka pattern same hai: install karo, app.use() karo.