app.js

var express = require('express');
var bodyParser = require('body-parser');
var sha1 = require('js-sha1');
var app = express();

var registeredDevices = [];

app.use('/jquery', express.static(__dirname + '/node_modules/jquery/dist/'));
app.use(bodyParser.json());

app.get('/', function(req, res) {
    res.sendFile(__dirname + '/index.html');

});

app.post('/', function(req, res) {
    var id = req.body.id;
    var hash = sha1(req.ip + id);

    var deviceVal = 0;
    /* Check if device is registered */
    registeredDevices.forEach(function(elem) {
        if (elem.id === hash)
            deviceVal = (++elem.count);
    });

    if (deviceVal <= 0) {
        var device = {
            id: hash,
            count: 1
        };
        var index = registeredDevices.push(device);
        console.log('Added device number: ' + (index + 1) + ' id: ' + hash);
    }

    var response = (deviceVal > 0 ? 'Access count: ' +
        deviceVal : 'New device added!');
    res.end(response);
});

var server = app.listen(3000, function() {
    var host = server.address().address;
    var port = server.address().port;

    console.log('Listening at http://%s:%s', host, port);
});