Express-session middleware in Express

express-session is middleware that manages user sessions — storing data on the server and tracking each visitor via a cookie. It's the backbone of login persistence in many Express apps.

Step 1: Create the project

mkdir session-demo
cd session-demo
npm init -y

Step 2: Install dependencies

npm i express
npm i express-session

Step 3: Write the app

// app.js
const express = require("express");
const session = require("express-session");
const app = express();
const port = 5100;

app.use(session({
    secret: "cart-secret-key",
    resave: false,
    saveUninitialized: true
}));

app.get("/add-to-cart", (req, res) => {
    req.session.cartItem = "Wireless Keyboard";
    res.send(`Item added! Now visit <a href="/cart">/cart</a> to view it.`);
});

app.get("/cart", (req, res) => {
    const item = req.session.cartItem || "Your cart is empty";
    res.send(`Cart contents: ${item}`);
});

app.listen(port, () => {
    console.log(`Server is running on http://localhost:${port}`);
});

Step 4: Run it

node app.js

Visiting /add-to-cart then /cart in the same browser shows the item persisted in the session, even though no database is involved.

Common uses

• Keeping a user logged in across requests.
• Building shopping-cart-like features without a full auth system.
• Storing temporary, per-visitor state on the server.