Express res.locals Property

The `res.locals` property is an object that holds response local variables specific to the current request. It has a scope limited to the request and is accessible only to the view(s) rendered during that particular request/response cycle, if any. 

Syntax:

res.locals

Parameter: No parameters. 

Return Value: Object 

Steps to Create the Application:

Step 1: Initialising the Node App using the below command:

npm init -y

Step 2: Installing the required packages:

npm i express body-parser

Project Structure:

The updated dependencies in package.json file will look like:

"dependencies": {
    "body-parser": "^1.20.2",
    "express": "^4.18.2",
}

Example 1: Below is the basic example of the res.locals property:

const express = require('express');
const app = express();
const PORT = 3000;

app.get('/',
    function (req, res) {
        res.locals.user = 'GeeksforGeeks';
        console.log(res.locals);
        res.end();
    });

app.listen(PORT,
    function (err) {
        if (err) console.log(err);
        console.log(
            "Server listening on PORT",
            PORT
        );
    });

Steps to run the program:

node index.js

Output: go to http://localhost:3000/, now you can see the following output on your console:

Server listening on PORT 3000
[Object: null prototype] { user: 'GeeksforGeeks' }

Example 2: Below is the basic example of the res.locals property:

const express = require('express');
const app = express();
const PORT = 3000;

app.get('/',
    function (req, res) {

        // Sending multiples locals
        res.locals.name = 'Gourav';
        res.locals.age = 13;
        res.locals.gender = 'Male'
        console.log(res.locals);
        res.end();
    });

app.listen(PORT,
    function (err) {
        if (err) console.log(err);
        console.log(
            "Server listening on PORT",
            PORT
        );
    });

Steps to run the program:

node index.js

Output: make a GET request to http://localhost:3000:

Server listening on PORT 3000
[Object: null prototype] { name: 'Gourav', age: 13, gender: 'Male' }

We have a complete reference article on response methods, where we have covered all the response methods to check those please go through Response Complete Reference article