getProtocolFromUrl static method
Implementation
static String getProtocolFromUrl(String urlString) {
  if (urlString.trim().isEmpty) {
    return '';
  }
  final uri = Uri.tryParse(urlString.trim());
  if (uri != null && uri.scheme.isNotEmpty) {
    final scheme = uri.scheme.toLowerCase();
    // Map https to http according to spec
    if (scheme == _httpsProtocol) {
      return _httpProtocol;
    }
    return scheme;
  }
  return '';
}