Step 1: single router

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

                        // Single routing
                        var 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);
                        });


                        

Step2 :multiple router

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

                        // Multiple routing
                        var router1 = express.Router();
                        var router2 = express.Router();
                        var 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();
                        });

                        router2.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);
                        });