Is it a fetch network error? (for the purpose of retrying on failure).

isNetworkError.js

/*
https://twitter.com/xinganwang/status/1189266788237885443

github/fetch: TypeError: Network request failed
Chrome: TypeError: Failed to fetch
Firefox: TypeError: NetworkError when attempting to fetch resource.
Safari: TypeError: The Internet connection appears to be offline.
*/

const isNetworkError = e =>
  /The Internet connection appears to be offline|Failed to fetch|Network request failed|NetworkError when attempting to fetch resource|The network connection was lost/.test(
    e.message
  ) ||
  e.statusCode === 502 ||
  e.statusCode === 504;