function isCloudflareRuntime() {
  // Since 2022-03-21 the `global_navigator` compatibility flag is on for Cloudflare Workers
  // which means that `navigator.userAgent` will be defined.
  // eslint-disable-next-line no-undef
  if (typeof navigator === 'object' && navigator !== null && typeof navigator.userAgent === 'string') {
    // eslint-disable-next-line no-undef
    return navigator.userAgent === 'Cloudflare-Workers'
  }
  // In case `navigator` or `navigator.userAgent` is not defined then try a more sneaky approach
  if (typeof Response === 'function') {
    const resp = new Response(null, { cf: { thing: true } })
    if (typeof resp.cf === 'object' && resp.cf !== null && resp.cf.thing) {
      return true
    }
  }
  return false
}
Are we running in a Cloudflare Worker?

@returns true if the code is currently running inside a Cloudflare Worker.