server.js

const { createServer } = require('http');
const next = require('next');
const routes = require('./routes');

const app = next({ dev: process.env.NODE_ENV !== 'production' });

const handler = routes.getRequestHandler(app);

app.prepare().then(() => {
  createServer(handler).listen(3000, (err) => {
    if (err) throw err;
    console.log('Ready on localhost:3000');
  });
});