server.js

// modules
const express = require('express');
const socketIO = require('socket.io');

//init port and dir
const port = process.env.PORT || 3000;
const index = '/index.html';

// init server
const server = express()
        .use((req, res) => {
            res.sendFile(index, { root: __dirname })
        })
        .listen(port, () =>{
            console.log(`Server started on port ${port}`)
        });
// init socketIO
const io = socketIO(server);

let users = [];
let currentPlayer = null;
let timeout = null;
const words = ['porte', 'tableau', 'pantoufle', 'lune', 'assiette', 'mamie'];

io.on('connection', (socket) => {
    socket.on('username', (username) => {
        console.log(`The user ${username} has joined the server`);
        socket.username = username;
        users.push(socket);
        sendUsers();
        if(users.length === 1 ) {
            currentPlayer = socket;
            switchPlayer();
        }
    });
    socket.on('disconnect', () => {
        users = users.filter((user) => {
            return user !== socket;
        });
        sendUsers();
        if(user.length === 0) {
            timeout = clearTimeout(timeout);
        }
    });
    socket.on('line', (data) => {
        socket.broadcast.emit('line', data);
    });
});

function sendUsers() {
    const usersData = users.map((user) => {
        return {
            username : user.username,
            isActive: user === currentPlayer
        }
    });
    io.emit('users', usersData);
}
function switchPlayer() {
    timeout = setTimeout(switchPlayer, 15000);

    const indexCurrentPlayer = users.indexOf(currentPlayer);
    currentPlayer = users[(indexCurrentPlayer + 1) % users.length];

    sendUsers();
    const nextWord = words[Math.floor(Math.random() * words.length)];
    currentPlayer.emit('word', nextWord);
    io.emit('clear');

}