An example using moment.js, bluebird.js and node.js

visitorCount.js

let moment = require('moment');
let http = require('http');
let url = require('url');
let bluebird = require('bluebird');
let fs = bluebird.promisifyAll(require('fs'));

let visitorCount = 0;
let users = [];

if (visitorCount == 0) {
    fs.readFileAsync('visitedUsers.json', 'utf8').then(function (data) {
        users = users.concat(JSON.parse(data));
        users.forEach(user => {
            visitorCount += user.visitCount;
        })
        console.log(data);
        console.log('Visitor Count ' + visitorCount);
    }).catch(function (err) {
        fs.unlinkAsync('visitedUsers.json')
            .then(function () {
                console.log('File deleted. New log file will be created');
            })
            .catch(function () {
                console.log('File could not be deleted.');
            })
    });
}

function createUser(_name) {
    let user = {
        name: _name,
        visitCount: 1,
        lastVisited: moment.now()
    };
    users.push(user);
}

function createForm() {
    return '<form action="register" method="get">User Name : <input type="text" name="name"><br><input type="submit" value="Submit"></form>';
}

function getPostFix(_num) {
    if (_num == 1) {
        return 'st';
    } else if (_num == 2) {
        return 'nd';
    } else if (_num == 3) {
        return 'rd';
    }
    else{
        return 'th';
    }
}

http.createServer((req, res) => {
    let output = '';
    if (req.url.startsWith('/register')) {
        let qData = url.parse(req.url, true).query;
        console.log(qData);
        if (qData.name != '') {
            if (users.length > 0) {
                let userExists = false;
                console.log(qData.name);
                users.forEach(user => {
                    if (user.name === qData.name) {
                        user.visitCount++;
                        user.lastVisited = moment.now();
                        userExists = true;
                    }
                });

                if (!userExists) {
                    createUser(qData.name);
                }
            } else {
                createUser(qData.name);
            }

            visitorCount++;

            fs.writeFileAsync('visitedUsers.json', JSON.stringify(users), function () {
                return 'Success';
            }).then(success => {
                console.log('File dumped.')
            }).catch(err => {
                console.log(err);
            })

        } else {
            output = 'No user defined. This visit will not be logged.<br>';
        }
        output += 'You are ' + visitorCount + getPostFix(visitorCount) + ' visitor. <br>' + users.length + ' visitors have visited till now. <br>';

        users.forEach(user => {
            output += user.name + ' visited for ' + user.visitCount + getPostFix(user.visitCount) + ' time ' + moment(user.lastVisited).fromNow() + '<br>';
        })
        res.writeHead(200, {
            'Content-Type': 'text/html'
        });
        res.write(createForm());
        res.write(output);        
        return res.end();
    } else {
        res.writeHead(200, {
            'Content-Type': 'text/html'
        });
        res.write(createForm());
        return res.end();
    }
}).listen(8080);


/*
- Every time a new user enters username, it updates the global visitor count and then registers the user
- If an exisitng user enters the username, it updates the global visitor count and user's visit count alongwith its visit time
- The page displays the info which contains user, its visit count and its last visit time.*/