robots.js

const defaultResponse = 'User-agent: *'

const disallowAll = `User-agent: *
Disallow: /`

export default function robots(req, res, next) {
  if (req.path !== '/robots.txt') return next()

  res.type('text/plain')

  // only include robots.txt when it's our production domain and adding localhost for robots-txt.js test
  if (req.hostname === 'docs.github.com' || req.hostname === '127.0.0.1') {
    return res.send(defaultResponse)
  }

  return res.send(disallowAll)
}