app.js

var express = require('express')
var app = express()

var expressMongoDb = require('express-mongo-db');
/**
 * Store database credentials in a separate config.js file
 * Load the file/module and its values
 * For MongoDB, we basically store the connection URL in config file
 */ 
var config = require('./config')
app.use(expressMongoDb(config.database.url));

/**
 * setting up the templating view engine
 */ 
app.set('view engine', 'ejs')

/**
 * import routes/index.js
 * import routes/users.js
 */ 
var index = require('./routes/index')
var users = require('./routes/users')

/**
 * Express Validator Middleware for Form Validation
 */ 
var expressValidator = require('express-validator')
app.use(expressValidator())

/**
 * body-parser module is used to read HTTP POST data
 * it's an express middleware that reads form's input 
 * and store it as javascript object
 */ 
var bodyParser = require('body-parser')
/**
 * bodyParser.urlencoded() parses the text as URL encoded data 
 * (which is how browsers tend to send form data from regular forms set to POST) 
 * and exposes the resulting object (containing the keys and values) on req.body.
 */ 
app.use(bodyParser.urlencoded({ extended: true }))
app.use(bodyParser.json())


/**
 * This module let us use HTTP verbs such as PUT or DELETE 
 * in places where they are not supported
 */ 
var methodOverride = require('method-override')

/**
 * using custom logic to override method
 * 
 * there are other ways of overriding as well
 * like using header & using query value
 */ 
app.use(methodOverride(function (req, res) {
  if (req.body && typeof req.body === 'object' && '_method' in req.body) {
    // look in urlencoded POST bodies and delete it
    var method = req.body._method
    delete req.body._method
    return method
  }
}))

/**
 * This module shows flash messages
 * generally used to show success or error messages
 * 
 * Flash messages are stored in session
 * So, we also have to install and use 
 * cookie-parser & session modules
 */ 
var flash = require('express-flash')
var cookieParser = require('cookie-parser');
var session = require('express-session');

app.use(cookieParser('keyboard cat'))
app.use(session({ 
	secret: 'keyboard cat',
	resave: false,
	saveUninitialized: true,
	cookie: { maxAge: 60000 }
}))
app.use(flash())

app.use('/', index)
app.use('/users', users)

app.listen(3000, function(){
	console.log('Server running at port 3000: http://127.0.0.1:3000')
})