webserver.js

let http = require('http').createServer(handler); //require http server, and create server with function handler()
let fs = require('fs'); //require filesystem module
let io = require('socket.io')(http) //require socket.io module and pass the http object (server)
let Gpio = require('onoff').Gpio; //include onoff to interact with the GPIO
let left = new Gpio(23, 'out');
let right = new Gpio(27, 'out');
let forward = new Gpio(17, 'out');
let reverse = new Gpio(22, 'out');

http.listen(8080); //listen to port 8080

function handler (req, res) { //create server
    fs.readFile(__dirname + '/public/index.html', function(err, data) { //read file index.html in public folder
        if (err) {
            res.writeHead(404, {'Content-Type': 'text/html'}); //display 404 on error
            return res.end("404 Not Found");
        }
        res.writeHead(200, {'Content-Type': 'text/html'}); //write HTML
        res.write(data); //write data from index.html
        return res.end();
    });
}

io.sockets.on('connection', function (socket) {// WebSocket Connection
    let initialvalueleft = 1; //static variable for current status
    let initialvalueright = 1;
    let initialvalueforward = 1;
    let initialvaluereverse = 1;
    socket.on('movement', function(data) {
        console.log(data)
        initialvalueleft = data.left;
        initialvalueright = data.right;
        initialvalueforward = data.forward;
        initialvaluereverse = data.reverse;

        if (initialvalueleft != left.readSync()) {
            left.writeSync(initialvalueleft);
        }
        if (initialvalueright != right.readSync()) {
            right.writeSync(initialvalueright);
        }
        if (initialvalueforward != forward.readSync()) {
            forward.writeSync(initialvalueforward);
        }
        if (initialvaluereverse != reverse.readSync()) {
            reverse.writeSync(initialvaluereverse);
        }
    });
});