code: function formatLine(startIndex) {
        let result = ' ';
  
        // Append a hex formatting of |bytes|.
        for (let i = 0; i < kBytesPerLine; ++i) {
          result += ' ';
  
          // Add a separator every 8 bytes.
          if ((i % 8) === 0) {
            result += ' ';
          }
  
          // Output hex for the byte, or space if no bytes remain.
          const byteIndex = startIndex + i;
          if (byteIndex < bytes.length) {
            result += byteToPaddedHex(bytes[byteIndex]);
          } else {
            result += '  ';
          }
        }
  
        result += '   ';
  
        // Append an ASCII formatting of the bytes, where ASCII codes 32
        // though 126 display the corresponding characters, nulls are
        // represented by spaces, and any other character is represented
        // by a period.
        for (let i = 0; i < kBytesPerLine; ++i) {
          const byteIndex = startIndex + i;
          if (byteIndex >= bytes.length) {
            break;
          }
  
          const curByte = bytes[byteIndex];
  
          if (curByte >= 0x20 && curByte <= 0x7E) {
            result += String.fromCharCode(curByte);
          } else if (curByte === 0x00) {
            result += ' ';
          } else {
            result += '.';
          }
        }
  
        return result;
      }
docs: Returns pretty printed kBytesPerLine bytes starting from bytes[startIndex], in hexdump style format.