Express res.cookie() Function

The res.cookie() function is used to set a cookie in the client's browser. It adds a Set-Cookie HTTP response header to the response. The cookie can contain a string value or an object, which Express serializes as JSON.

Syntax:

res.cookie(name, value [, options])

Parameters:

• name: The name of the cookie.
• value: The value of the cookie. It can be a string, number, object, or other supported value.
• options (Optional): An object used to configure the cookie, such as maxAge, expires, domain, path, httpOnly, secure, and sameSite. 

Return Value: Returns the response object (res), allowing method chaining.

Installation of the Express Module:

Step 1: You can install this package by using this command.

npm install express

Step 2: After installing the express module, you can check your express version in the command prompt using the command.

npm version express

Step 3: Create a folder and add a file named index.js. Run the file using:

node index.js

Project Structure:

Example 1: Below is the code example of the res.cookie() Function.

const express = require('express');
const app = express();
const PORT = 3000;
app.get('/', (req, res) => {
    res.cookie('name', 'GeeksforGeeks');
    res.send('Cookie Set');
});
app.listen(PORT, () => {
    console.log(`Server listening on PORT ${PORT}`);
});

Steps to run the program:

node index.js

Output:

Console Output:

Server listening on PORT 3000

Browser Output: Visit http://localhost:3000/ . You will see:

Example 2: Below is the code example of the res.cookie() Function.

const express = require('express');
const app = express();
const PORT = 3000;
app.get('/', (req, res) => {
    res.cookie('title', 'GeeksforGeeks', {
        maxAge: 60000,
        httpOnly: true
    });
    res.send('Cookie Set with Options');
});
app.listen(PORT, () => {
    console.log(`Server listening on PORT ${PORT}`);
});

Steps to run the program:

Run the index.js file using the below command:

node index.js

Output:

Console Output:

Server listening on PORT 3000

Browser Output: Visit http://localhost:3000/ . You will see:

Working of res.cookie()

• An Express application receives a client request.
• The route handler gets access to the response object through res.
• res.cookie() creates a Set-Cookie response header.
• The browser receives the response and stores the cookie according to its attributes.
• The cookie can be sent back to the server in subsequent requests when its conditions are satisfied.

Use Cases of res.cookie()

• Storing session identifiers.
• Managing user preferences.
• Maintaining authentication-related cookies.
• Storing temporary client-side state.
• Configuring cookie security and expiration behavior.