code: function formatSize(sizeBytes) {
      if (sizeBytes < 1024) {
          return sizeBytes + ' B';
      }
      var i, sizeVal = sizeBytes, precision = 1;
      for (i = 0; sizeVal >= 1024; i += 1) {
          sizeVal /= 1024;
      }
      // If we are just reporting a low number, no need for decimal places.
      if (sizeVal < 10) {
          precision = 3;
      } else if (sizeVal < 100) {
          precision = 2;
      }
      return sizeVal.toFixed(precision) + ' ' +
          ['B', 'kB', 'MB', 'GB', 'TB'][Math.min(i, 4)];
  }
docs: Format a size in bytes into a human-readable string with metric unit
  prefixes.