generateMessageVector = (message) => {
  return mtrx.generate(
    [message.length, 1],
    // Callback to get a value of each matrix cell.
    // The order the matrix is being filled in is from left to right, from top to bottom.
    (cellIndices) => {
      const rowIndex = cellIndices[0];
      return message.codePointAt(rowIndex) % alphabetCodeShift;
    },
  );
}
Generates a message vector from a given message.

@param {string} message - the message to encrypt.
@return {number[][]} messageVector