CS 602 Server Side development hw3 please explain and comment the following node.js code

var express = require('express'); var bodyParser = require('body-parser'); var handlebars = require('express-handlebars');

var app = express();

// setup handlebars view engine app.engine('handlebars', handlebars({defaultLayout: 'main_logo'})); app.set('view engine', 'handlebars');

// static resources app.use(express.static(__dirname + '/public'));

app.use(bodyParser.json()); app.use(bodyParser.urlencoded({ extended: false }));

// Routing var routes = require('./partb_routes/index'); app.use('/', routes);

app.use(function(req, res) { res.status(404); res.render('404'); });

app.listen(3000, function(){ console.log('http://localhost:3000'); });