The dev property

export default {
  dev: process.env.NODE_ENV !== 'production'
}

const { Nuxt, Builder } = require('nuxt')
const app = require('express')()
const port = process.env.PORT || 3000

// We instantiate Nuxt with the options
const config = require('./nuxt.config.js')
const nuxt = new Nuxt(config)
app.use(nuxt.render)

// Build only in dev mode
if (config.dev) {
  new Builder(nuxt).build()
}

// Listen the server
app.listen(port, '0.0.0.0').then(() => {
  console.log(`Server is listening on port: ${port}`)
})

{
  "scripts": {
    "dev": "node server.js",
    "build": "nuxt build",
    "start": "NODE_ENV=production node server.js"
  }
}