req.cookies with cookie-parser in Express

Introduction

We use req.cookies to easily read cookies sent by the browser. The cookie-parser middleware helps Express understand these cookies.

When you want to remember a user's preferences like theme or language.

When you need to check if a user is logged in by reading a session cookie.

When you want to track user visits or behavior with cookies.

When you want to customize content based on stored cookie data.

When you want to read cookies without manually parsing HTTP headers.

Syntax

Express

const cookieParser = require('cookie-parser');
app.use(cookieParser());

app.get('/', (req, res) => {
  const cookies = req.cookies;
  // use cookies object
});

Call app.use(cookieParser()) before your routes to enable cookie parsing.

req.cookies is an object where each cookie name is a key and its value is the cookie value.

Examples

This logs all cookies sent by the browser as an object.

Express

app.use(cookieParser());

app.get('/', (req, res) => {
  console.log(req.cookies);
  res.send('Check console for cookies');
});

This reads a cookie named username and greets the user by name or as 'Guest' if no cookie.

Express

app.get('/greet', (req, res) => {
  const name = req.cookies.username || 'Guest';
  res.send(`Hello, ${name}!`);
});

This checks a cookie loggedIn to decide what message to show.

Express

app.get('/check', (req, res) => {
  if (req.cookies.loggedIn === 'true') {
    res.send('Welcome back!');
  } else {
    res.send('Please log in.');
  }
});

Sample Program

This Express app sets a cookie named username with value 'Alice' at /setcookie. Then at /showcookie, it reads and shows the cookie value using req.cookies.

Express

const express = require('express');
const cookieParser = require('cookie-parser');

const app = express();
app.use(cookieParser());

app.get('/setcookie', (req, res) => {
  res.cookie('username', 'Alice');
  res.send('Cookie has been set');
});

app.get('/showcookie', (req, res) => {
  const user = req.cookies.username || 'No cookie found';
  res.send(`Username cookie value: ${user}`);
});

app.listen(3000, () => {
  console.log('Server running on http://localhost:3000');
});

Important Notes

Cookies are sent by the browser with each request, so req.cookies is available only after cookie-parser middleware runs.

Cookies are strings. If you store JSON, you need to parse it yourself.

For security, avoid storing sensitive info directly in cookies.

Summary

req.cookies holds cookies sent by the browser as an object.

cookie-parser middleware must be used to fill req.cookies.

Use cookies to remember user info or preferences easily.