uploadprogress_get_info example

  public function progress($key) {
    $progress = [
      'message' => $this->t('Starting upload...'),
      'percentage' => -1,
    ];

    $implementation = file_progress_implementation();
    if ($implementation == 'uploadprogress') {
      $status = uploadprogress_get_info($key);
      if (isset($status['bytes_uploaded']) && !empty($status['bytes_total'])) {
        $progress['message'] = $this->t('Uploading... (@current of @total)', [
          '@current' => format_size($status['bytes_uploaded']),
          '@total' => format_size($status['bytes_total']),
        ]);
        $progress['percentage'] = round(100 * $status['bytes_uploaded'] / $status['bytes_total']);
      }
    }

    return new JsonResponse($progress);
  }

}