server.js

/**
 * Credit Card Check App - server.js
 */

"use strict";

// Include modules
var express = require('express');
var bodyParser = require('body-parser');

var app = express();

app.use(express.static(__dirname + '/'));
app.use(bodyParser.json());

/**
 * Handle POST request from client.
 */
app.post('/api/cc', function(req, res) {

    /**
	* Note: - Only credit card number is being validated
	* Expiry date, Expiry year, CSV is not being validated
	*/
    var CCApp = {};
    CCApp.number = req.body.ccnumber;   // Store credit card number from the request.

   /**
    * Validates the credit card number using the Luhn10 algorithm.
    *
    * @param {Number} number Credit card number.
    * @returns {Boolean}
    * Credits: Online resources
    */
    CCApp.validateCC = function() {

        var sum = 0;
        var numdigits = this.number.length;
        var parity = numdigits % 2;

        for(var i=0; i < numdigits; i++) {
          var digit = parseInt(this.number.charAt(i));
          if(i % 2 == parity) digit *= 2;   // Double every other digits
          if(digit > 9) digit -= 9;
          sum += digit;
        }

       return (sum % 10) == 0;
    }

   /**
    * Find out the card type using card length and starting seq number.
    *
    * @param {Number} number Credit card number.
    * @returns {String}
    */
    CCApp.findOutCardType = function() {

        var length = this.number.length;

       if ((/^(4)/.test(this.number)) && ((length == 13) || (length == 16) || (length == 19))) {
          return 'Visa';
        } else if ((/^3[47]/.test(this.number)) && (length == 15)) {
          return 'American Express';
        } else if ((/^5[1-5]/.test(this.number)) && (length == 16)) {
          return 'MasterCard';
        } else {
          return 'Unknown';
        }
    }

   /**
    * Send response to the client after credit card validation.
    * @returns {status, type} object
    */
    res.send({
        status: CCApp.validateCC(),
        type: CCApp.findOutCardType()
    });
});

/**
 * Start Listening request
 */
var port = process.env.PORT || 3000;

app.listen(port);

console.log('Server is listening on port : ' + port );