Next.js 14 App Router Custom Server with Express

Vercel / Next .js no longer publish an example custom webserver for Next.js 14 App router.

There is a discussion here https://github.com/vercel/next.js/discussions/49326 - and a few 'hidden' Medium posts, but none that show a clear Express / Next.js 14 App router configuration. 

As with Next 13 and the Pages example that Vercel have published, if you create a custom server you will not be able to deploy to Vercel.

Below is the server which is a typescript file - server.ts placed below a src directory (but at the same level and outside the app directory.

Note that Next.js 14 built via Webpack is still a CommonJS application, and so we cannot use Node.js ESM top-level await.

import dotenv from 'dotenv'
import next from 'next'
import nextBuild from 'next/dist/build'
import path from 'path'

// This will depend on whether your server.ts file and general
// app setup is located below a src folder or not.
dotenv.config({
  path: path.resolve(__dirname, '../.env'),
})

import express from 'express'

const app = express()
const PORT = process.env.PORT || 3000

const start = async (): Promise<void> => {
  if (process.env.NEXT_BUILD) {
    app.listen(PORT, async () => {
      console.log(`Next.js is now building...`)
      // @ts-expect-error
      await nextBuild(path.join(__dirname, '..'))
      process.exit()
    })

    return
  }

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

  const nextHandler = nextApp.getRequestHandler()

  app.use((req, res) => nextHandler(req, res))

  nextApp.prepare().then(() => {
    console.log('Next.js started')

    app.listen(PORT, async () => {
      console.log(`Next.js App URL: ${process.env.NEXT_SERVER_URL}`)
    })
  })
}

start()

Hope this helps...