How to use the express-handlebars function in express-handlebars

init(){
    // -> Set the folder for html views & disable powered-by header
    this.express.engine('html', hbs({ extname: 'html' }));
    this.express.set('views', process.cwd() + '/src/server/views');
    this.express.set('view engine', 'html');
    this.express.locals.settings['x-powered-by'] = false;
    this.express.disable('x-powered-by');
  }

// Templates
app.use(templatesHelper);

// Cookies / Session / User
app.use(cookieParser());
app.use(sessionHelper);
app.use(userHelper);

// BodyParser
app.use(logger('dev'));
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: false }));
app.use(express.static(path.join(__dirname, 'public')));

// Handlebars setup
app.engine($views().engine, exphbs({
  defaultLayout: $views().layout,
  extname: $views().extension,
  helpers: hbsHelper,
  layoutsDir: path.join(__dirname, '/views/layouts'),
  partialsDir: path.join(__dirname, '/views/partials')
}));

// view engine setup
app.set('views', path.join(__dirname, 'views'));
app.set('view engine', $views().engine);

// Router
router(app);

// Listening port...
app.listen($serverPort() || 3000);

import * as hbsHelper from '../lib/handlebars';

// Utils
import { isMobile } from '../lib/utils/device';

// Environment
const isDevelopment = process.env.NODE_ENV !== 'production';

// Express app
const app = express();

// Public
app.use(express.static(path.join(__dirname, '../public')));

// Handlebars setup
app.engine(config.views.engine, exphbs({
  extname: config.views.extension,
  helpers: hbsHelper
}));

// View Engine Setup
app.set('views', path.join(__dirname, config.views.path));
app.set('view engine', '.hbs');

// Webpack Compiler
const webpackCompiler = webpack(webpackConfig);

if (isDevelopment) {
  app.use(webpackDevMiddleware(webpackCompiler));
  app.use(webpackHotMiddleware(webpackCompiler));
}

res.redirect(
            301,
            url.format({
                pathname: `${req.path}/`,
                query: req.query,
            })
        );
    } else {
        next();
    }
});

// Setup hbs
app.engine(
    '.hbs',
    handlebars({
        defaultLayout: 'main',
        extname: '.hbs',
        helpers,
    })
);
app.set('view engine', '.hbs');

if (config.ENV.prod) {
    app.enable('view cache');
}

app.use('*', cors);
app.use('/', routes);
app.use(redirects);

// Remove cache control so we don't cache 4XX + routes

.set('filename', path)
            .set('compress', true)
            .use(stylusDefinitions);
        }
      })
    );
  }

  // BodyParser
  app.use(logger('dev'));
  app.use(bodyParser.json());
  app.use(bodyParser.urlencoded({ extended: false }));
  app.use(express.static(path.join(__dirname, '../../public')));

  // Handlebars setup
  app.engine($views().engine, exphbs({
    extname: $views().extension,
    helpers: hbsHelper,
    layoutsDir: path.join(__dirname, '/../../views/layouts'),
    partialsDir: path.join(__dirname, '/../../views/partials')
  }));

  // view engine setup
  app.set('views', path.join(__dirname, '/../../views'));
  app.set('view engine', $views().engine);

  // Imports
  imports(app);

  // Router
  router(app);

// --------------------------------------------------
import path from 'path';
app.use(express.static(path.resolve(process.cwd(), 'dist')));

app.use('/favicon.ico', function (req, res) {
  res.redirect('http://github.com/favicon.ico');
});

// View engine
// --------------------------------------------------
import expressHandlebars from 'express-handlebars';
import handlebars from 'handlebars';

handlebars.registerHelper('json-stringify', ::JSON.stringify);

app.engine('hbs', expressHandlebars());
app.set('view engine', 'hbs');

// Proxy to API server
// --------------------------------------------------
import url from 'url';

app.use('/api/*', proxy(config.apiServer.urlPrefix, {
  forwardPath: req => {
    return url.parse(req.originalUrl).path.replace(/^\/api/, '');
  }
}));


// Render layout
// --------------------------------------------------
import render from '../lib/render';

'use strict';

import path from 'path';
import express from 'express';
import exphbs from 'express-handlebars';
import request from 'superagent';

import router from './router';

const app = express();

app.engine('handlebars', exphbs({
  layoutsDir: path.join(__dirname, '/views/layouts'),
  defaultLayout: 'index'
}));
app.set('view engine', 'handlebars');
app.set('views', path.join(__dirname, '/views'));

app.use('/assets/img', express.static(path.resolve(path.join(__dirname, '/../dist/img/'))));
app.use('/assets/js', express.static(path.resolve(path.join(__dirname, '/../dist/js'))));
app.use('/assets/css', express.static(path.resolve(path.join(__dirname, '/../dist/css'))));

app.use(router);
app.listen(3000);

console.log('Application started on port 3000');

function main() {

    const snipers = new SnipersTableModel();
    const portfolio = new SniperPortfolio();
    portfolio.addListener(snipers);
    const sniperLauncher = new SniperLauncher(portfolio, process.argv[2]);

    const app = express();
    const urlencodedParser = bodyParser.urlencoded({extended: false});
    app.engine('.handlebars', handlebars());
    app.set('view engine', '.handlebars');
    app.set('views', __dirname + '/views');

    app.get('/', function (req, res) {
        res.render('main', {table: snipers.table()});
    });

    app.post('/', urlencodedParser, function (req, res) {
        const itemId = req.body["new-item-id"];
        sniperLauncher.joinAuction(itemId);

        res.redirect("/");
    })

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

store: new RedisStore({ client: storage.client }),
  secret: config.session.secret,
  key: appMeta.name,
  cookie: { secure: env !== 'development' },
  resave: true,
  logErrors: true,
  saveUninitialized: true,
});

app.use(sessionMiddleware);

io.use((socket, next) => sessionMiddleware(socket.request, socket.request.res, next));

app.engine(
  'hbs',
  exphbs({
    defaultLayout: 'index',
    extname: '.hbs',
    layoutsDir: 'src/views/',
  }),
);

app.set('view engine', 'hbs');
app.set('views', 'src/views');
app.set('port', process.env.PORT || 3000);

app.get('/', (req, res) => {
  res.render('index', {
    name: 'index',
  });
});

export default (app) => {
  app.set('views', path.join(__dirname, '../views'));
  app.engine('handlebars', exphbs({defaultLayout: 'main'}));
  app.set('view engine', 'handlebars');
  app.use(compression());
  app.use(bodyParser.json());
  app.use(bodyParser.urlencoded({ extended: false }));
  app.use(express.static('public'));
  app.use(cookieParser());

  app.use(session({
    'secret': process.env.SESSION_SECRET,
    'cookie': {'maxAge': 1209600000},
    'store': new MongoStore({
      url: process.env.MONGOLAB_URI,
      autoReconnect: true
    }),
    'resave': true,
    'saveUninitialized': true