Simple Hot-Reload server

client.js

const hotReload = (address, options = {}) => {
    // Константы
    const CONST_RELOAD_MESSAGE = 'HOT_RELOAD_NOW';
    // Настройки
    const reconnect_timeout = options.reconnect_timeout || 500;
    const reconnect_tries = options.reconnect_tries || 5;
    // Локальные переменные
    let socket = null;
    let current_tries = 0;

    onOpen = () => {
        current_tries = 0;					
        options.callback('CONNECTED');
    };

    onClose = () => {					
        if (current_tries > reconnect_tries) {
                if (options.callback != null) options.callback('ERROR');
                return;
        }
        if (options.callback != null) options.callback('WARNING');
        setTimeout(() => {
            initSocket();
            current_tries++;
        }, reconnect_timeout);
    };

    onMessage = event => {
        const message = event.data;
        if (message === CONST_RELOAD_MESSAGE) {
            socket.close();
            document.location.reload();
        }
    };

    initSocket = () => {
        socket = new WebSocket(address);
        socket.onopen = onOpen;
        socket.onclose = onClose;
        socket.onmessage = onMessage;
    }
    initSocket();
}

module.exports = hotReload;

server.js

'use strict';
const watch = require('watch');
const express = require('express');
const app = express();
const expressWs = require('express-ws')(app);

const public_dir = path.join(__dirname, '/public');
app.use(express.static(public_dir));

// Механизм горячей перезагрузки на клиенте при изменении любого HTML файла
app.ws('/hot-reload', _ => {});
const wsClients = expressWs.getWss().clients;
watch.watchTree(public_dir, {interval: 0.5}, (f) => {
    if (typeof f !== 'string') return;
    wsClients.forEach(ws => ws.send("HOT_RELOAD_NOW"));
});

app.set('port', process.env.PORT || 3000);

app.listen(app.get('port'), () => {
  console.log('Started Express server *:' + app.get('port'));  
});