Express express.Router() Function

The express.Router() function is used to create a new router object. This function is used when you want to create a new router object in your program to handle requests. 

Syntax:

express.Router( [options] )

Optional Parameters:

• case-sensitive: This enables case sensitivity.
• mergeParams: It preserves the req.params values from the parent router.
• strict: This enables strict routing.

Return Value: This function returns the New Router Object. 

Steps to Install 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: After that, you can just create a folder and add a file, for example, index.js. To run this file you need to run the following command.

node index.js

Project Structure:

Project Structure

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

"dependencies": {
    "express": "^4.18.2",
}

Example 1: Below is the code of express.Router() Function implementation.

javascript

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

// Single routing
const router = express.Router();

router.get('/', function (req, res, next) {
    console.log("Router Working");
    res.end();
})

app.use(router);

app.listen(PORT, function (err) {
    if (err) console.log(err);
    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:

Now open your browser and go to http://localhost:3000/, you will see the following output on your screen:

Server listening on PORT 3000
Router Working

Example 2: Below is the another code example of express.Router() Function implementation.

javascript

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

// Multiple routing
const router1 = express.Router();
const router2 = express.Router();
const router3 = express.Router();

router1.get('/user', function (req, res, next) {
    console.log("User Router Working");
    res.end();
});

router2.get('/admin', function (req, res, next) {
    console.log("Admin Router Working");
    res.end();
});

router3.get('/student', function (req, res, next) {
    console.log("Student Router Working");
    res.end();
});

app.use(router1);
app.use(router2);
app.use(router3);

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

Steps to run the  program: Run the index.js file using the below command:

node index.js

Now make a GET request to http://localhost:3000/user, http://localhost:3000/admin, and http://localhost:3000/student, then you will see the following output on your console:

Output:

Server listening on PORT 3000
User Router Working
Admin Router Working
Student Router Working