Express Middleware

Request coming
       │
       ▼
[Middleware 1] ── next() ──► [Middleware 2] ── next() ──► [Route Handler]
       ▲                          ▲
       └─── response lo pass ─────┘
                              │
                              ▼
                        Response send

// Simple logger middleware
const logger = (req, res, next) => {
  const start = Date.now();
  console.log("➡️", req.method, req.url);

  res.on("finish", () => {
    const ms = Date.now() - start;
    console.log("⬅️", res.statusCode, ms + "ms");
  });

  next();
};

module.exports = logger;

const express = require("express");
const logger = require("./middleware/logger");

const app = express();
app.use(logger); // সব routes-এ apply

app.get("/", (req, res) => {
  res.send("Middleware আছি!");
});

// নির্দিষ্ট path-এ middleware
app.use("/api", require("./middleware/apiAuth"));

// Body parsing — JSON
app.use(express.json());

// Body parsing — URL encoded form
app.use(express.urlencoded({ extended: true }));

// Static files
app.use(express.static("public"));

// Raw data
app.use(express.raw({ type: "application/octet-stream" }));

npm install cors helmet morgan compression

const cors = require("cors");
const helmet = require("helmet");
const morgan = require("morgan");
const compression = require("compression");

app.use(helmet());           // security headers
app.use(cors());             // cross-origin
app.use(morgan("dev"));      // logging
app.use(compression());      // gzip compression