server.js

/**
 * This is an Express server to host the files within the `dist` directory
 * while the app is under test. It is recommended to use this script to
 * serve the app because other servers like `http-server` and python's
 * `SimpleHTTPServer` will force a redirect and re-add the trailing slash
 * when the `static/js/removeTrailingSlash.js` script executes on initial
 * page load.
 */
const path = require('path')
const express = require('express')
const fs = require('fs')

const app = express()

const PORT = 3000

const getRequestDuration = (start) => {
  const NS_PER_SEC = 1e9
  const NS_TO_MS = 1e6
  const diff = process.hrtime(start)

  return (diff[0] * NS_PER_SEC + diff[1]) / NS_TO_MS
}

const logger = (req, res, next) => {
  const durationMs = getRequestDuration(process.hrtime())
  const message = `[${new Date().toISOString()}] ${req.method}:${req.url} ${
    res.statusCode
  } ${durationMs.toLocaleString()} ms`

  // eslint-disable-next-line no-console
  console.log(message)
  next()
}

const DIRECTORY_TO_SERVE = path.join(__dirname, '../dist')

app.use((req, _res, next) => {
  const maybeDirectory = `${DIRECTORY_TO_SERVE}${req.path}`

  if (fs.lstatSync(maybeDirectory).isDirectory()) {
    req.url += '/index.html'
  }

  next()
})

app.use(
  express.static(DIRECTORY_TO_SERVE, {
    index: 'index.html',
    redirect: false,
    extensions: ['html'],
  })
)

app.use(logger)

app.listen(PORT, () => {
  if (process.send) {
    process.send('ready')
  }

  // eslint-disable-next-line no-console
  console.log(`Server listening on port ${PORT}.`)
})