How to manipulate cookies by using ‘Response.cookie()’ in Express?

Cookies are small data that is stored on the client’s computer. Using this cookie various tasks like authentication, session management, etc can be done. In Express JS we can use the cookie-parser middleware to manage the cookies in the application. In this article, we going to manipulate cookies in Express JS by using the two scenarios/approaches below.

Prerequisites

• Express JS
• Postman

The two ways we can manipulate the cookies are discussed below:

Approach 1: Updating Cookie Value

In this apporach, we will modify the existing cookie information that is stored in the user’s browser. By using the res.cookie() method in Express.js, we will set a new value for the cookie

Syntax:

res.cookie('cookieName', 'newCookieValue');

Example: In the below example, firstly we have defined the route /setCookie which sets the cookie value as “Geek“. Then we update the cookie value in the route /updateCookie by using the res.cookie() method. We have updated the cookie value from “Geek” to “GeeksforGeeks“.

Javascript

//app.js

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

// use cookie-parser middleware
app.use(cookieParser());

// route to set the initial cookie
app.get('/setCookie', (req, res) => {
    res.cookie('user', 'Geek');
    res.send('Cookie has been set!');
});

// route to update the cookie value
app.get('/updateCookie', (req, res) => {
    // ensure the 'user' cookie is set before updating
    const currUserValue = req.cookies.user;
    if (!currUserValue) {
        return res.status(400).send('Please set the cookie first by visiting /setCookie');
    }
    // update the cookie value
    res.cookie('user', 'GeeksforGeeks');
    res.send('Cookie has been updated!');
});

app.listen(3000, () => {
    console.log('Server is running on port 3000');
});

Output:

Approach 2: Deleting Cookie Value

In this apporach, we will delete the cookie which is already set in the Express.js application. Firstly, we define the route to set the cookie and then we will perform the deletion of the cookie using the res.cookie() method.

Syntax:

res.cookie('cookieName', '', { expires: new Date(0) });

Example: In the below example, we have set the route /setCookie to set the cookie as “Geek“, then we have set another new route as /deleteCookie to delete the cookie which was set. For deleting the cookie, we are passing an empty value wit the immediate expiration in the res.cookie() method.

Javascript

//app.js

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

// use cookie-parser middleware
app.use(cookieParser());

// route to set a cookie
app.get('/setCookie', (req, res) => {
    res.cookie('user', 'Geek');
    res.send('Cookie has been set!');
});

// route to delete the cookie
app.get('/deleteCookie', (req, res) => {
    // ensure the 'user' cookie is set before deleting
    const currUserValue = req.cookies.user;
    if (!currUserValue) {
        return res.status(400).send('Please set the cookie first by visiting /setCookie');
    }
    // delete the cookie by setting an empty value and an immediate expiration
    res.cookie('user', '', { expires: new Date(0) });
    res.send('Cookie has been deleted!');
});
a
pp.listen(3000, () => {
    console.log('Server is running on port 3000');
});

Output:

Conclusion

Managing the cookies in the Express JS application is an important task as the cookies consist of information that is used for various takes including authentication. The middleware cookie parser in Express JS makes the tasks of cookie modification easier in the Express JS applications.