server.js

import fs from 'fs'
import path from 'path'
import { fileURLToPath } from 'url'
import express from 'express'
import { createServer as createViteServer } from 'vite'

const __dirname = path.dirname(fileURLToPath(import.meta.url))

async function createServer() {
    const app = express()

    // Create Vite server in middleware mode and configure the app type as
    // 'custom', disabling Vite's own HTML serving logic so parent server
    // can take control
    const vite = await createViteServer({
        server: { middlewareMode: true },
        appType: 'custom'
    })

    // Use vite's connect instance as middleware. If you use your own
    // express router (express.Router()), you should use router.use
    app.use(vite.middlewares)

    app.use('*', async (req, res, next) => {
        const url = req.originalUrl

        try {
            // 1. Read index.html
            let template = fs.readFileSync(
                path.resolve(__dirname, 'index.html'),
                'utf-8',
            )

            // 2. Apply Vite HTML transforms. This injects the Vite HMR client,
            //    and also applies HTML transforms from Vite plugins, e.g. global
            //    preambles from @vitejs/plugin-react
            template = await vite.transformIndexHtml(url, template)

            // 3. Load the server entry. ssrLoadModule automatically transforms
            //    ESM source code to be usable in Node.js! There is no bundling
            //    required, and provides efficient invalidation similar to HMR.
            const { render } = await vite.ssrLoadModule('/src/entry-server.js')

            // 4. render the app HTML. This assumes entry-server.js's exported
            //     `render` function calls appropriate framework SSR APIs,
            //    e.g. ReactDOMServer.renderToString()
            const appHtml = await render(url)

            // 5. Inject the app-rendered HTML into the template.
            const html = template.replace(`<!--ssr-outlet-->`, appHtml)

            // 6. Send the rendered HTML back.
            res.status(200).set({ 'Content-Type': 'text/html' }).end(html)
        } catch (e) {
            // If an error is caught, let Vite fix the stack trace so it maps back
            // to your actual source code.
            vite.ssrFixStacktrace(e)
            next(e)
        }
    })

    app.listen(2255)
}

createServer()