Cookie Best Practices in Express.js

1. Introduction

Goal of the Tutorial

This tutorial aims to equip you with the best practices for handling cookies in Express.js, a popular web application framework for Node.js. We will go over the process of setting, securing, and optimizing cookies.

What You Will Learn

By the end of this tutorial, you'll understand how to:

• Set, read, and delete cookies
• Secure cookies to prevent attacks
• Optimize cookie performance

Prerequisites

This tutorial assumes that you have a basic understanding of JavaScript and Node.js, and that you're familiar with Express.js.

2. Step-by-Step Guide

Understanding Cookies

Cookies are small pieces of data stored on the client's browser. They are used to remember stateful information for the stateless HTTP protocol.

In Express.js, we use the cookie-parser middleware to work with cookies.

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

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

Setting a Cookie

To set a cookie, we use the response.cookie() method.

app.get('/', (req, res) => {
  res.cookie('name', 'express').send('cookie set'); // Sets name=express cookie.
});

Reading a Cookie

To read cookies, you simply use request.cookies.

app.get('/', (req, res) => {
  console.log('Cookies: ', req.cookies);
});

3. Code Examples

Securely Setting a Cookie

Here, we'll set a cookie with the httpOnly and secure options. httpOnly prevents the cookie from being accessed through client-side scripts, while secure ensures the cookie is sent over HTTPS.

app.get('/', (req, res) => {
   res.cookie('name', 'express', { secure: true, httpOnly: true }).send('cookie set');
});

Deleting a Cookie

To delete a cookie, you use the response.clearCookie() method.

app.get('/clear_cookie', (req, res) => {
   res.clearCookie('name');
   res.send('cookie name cleared');
});

4. Summary

In this tutorial, you have learned how to set, secure, read, and delete cookies in Express.js. You also learned how to use the cookie-parser middleware.

Next, you could learn about sessions in Express.js, which is a related subject. For more information, consult the Express.js documentation and this article on the cookie-parser package.

5. Practice Exercises

1. Exercise: Set a cookie named userID with a value of 1234 and then read it.

Solution:
js app.get('/', (req, res) => { res.cookie('userID', '1234').send('cookie set'); console.log('Cookies: ', req.cookies); });

1. Exercise: Set a cookie named sessionID with a value of abcd, make it secure and httpOnly. Afterwards, try to delete it.

Solution:
```js
app.get('/', (req, res) => {
res.cookie('sessionID', 'abcd', { secure: true, httpOnly: true }).send('cookie set');
});

app.get('/clear_cookie', (req, res) => {
res.clearCookie('sessionID');
res.send('cookie sessionID cleared');
});
```

1. Exercise: Set multiple cookies and read them all at once.

Solution:
js app.get('/', (req, res) => { res.cookie('name', 'express'); res.cookie('userID', '1234'); res.cookie('sessionID', 'abcd'); res.send('cookies set'); console.log('Cookies: ', req.cookies); });

Remember to keep practicing and exploring more functionalities of cookies in Express.js!