code: function toHexString(number, numberOfBytes) {
    numberOfBytes = numberOfBytes || 1;
    let hexString = '00'.repeat(numberOfBytes) + number.toString(16);
  
    return hexString.substr(-2 * numberOfBytes);
  }
docs: Convert the given number to a hexadecimal string of the given length.
  @param {Number} number The given number.
  @param {Number} numberOfBytes The number of bytes of hex string.
  @return {String} The resulting hexadecimal string.