server.js

import { promises as fs } from 'fs';
import express from 'express';

// Constants
const isProduction = process.env.NODE_ENV === 'production';
const port = process.env.PORT || 4000;
const base = process.env.BASE || '/';

// Cached production assets
const ssrManifest = isProduction
  ? await fs.readFile('./dist/client/.vite/ssr-manifest.json', 'utf-8')
  : undefined;

// Create http server
const app = express();

// Add Vite or respective production middlewares
let vite;
if (!isProduction) {
  const { createServer } = await import('vite');
  vite = await createServer({
    server: { middlewareMode: true },
    appType: 'custom',
    base
  });
  app.use(vite.middlewares);
} else {
  const compression = (await import('compression')).default;
  const sirv = (await import('sirv')).default;
  app.use(compression());
  app.use(base, sirv('./dist/client', { extensions: [] }));
}

app.use('/scripts', express.static('./src/scripts'));
app.use('/styles', express.static('./src/styles'));

app.use('*', async (req, res) => {
  try {
    const url = req.originalUrl.replace(base, '');

    let template;
    let render;
    if (!isProduction) {
      template = await fs.readFile('./index.html', 'utf-8');
      template = await vite.transformIndexHtml(url, template);
      render = (await vite.ssrLoadModule('/src/entry-server.js')).render;
    }

    const rendered = await render(url, ssrManifest);

    const html = template
      .replace(`<!--app-head-->`, rendered.head ?? '')
      .replace(`<!--app-html-->`, rendered.html ?? '');

    res.status(200).set({ 'Content-Type': 'text/html' }).send(html);
  } catch (e) {
    vite?.ssrFixStacktrace(e);
    console.log(e.stack);
    res.status(500).end(e.stack);
  }
});

// Start http server
app.listen(port, () => {
  console.log(`Server started at http://localhost:${port}`);
});