Discussion on: Daily Challenge #47 - Alphabets

"use strict";

function lettersOnly(letterOrElse) {
  return letterOrElse.toUpperCase() !== letterOrElse.toLowerCase();
}

function toAlphabetPosition(letter) {
  return letter.toLowerCase().charCodeAt(0) - 'a'.charCodeAt(0) + 1;
}

function alphabet_position(input) {
  return Array
    .from(input)
    .filter(lettersOnly)
    .map(toAlphabetPosition)
    .join(" ");
}

const result = alphabet_position("The sunset sets at twelve o' clock.");
const expectations = "20 8 5 19 21 14 19 5 20 19 5 20 19 1 20 20 23 5 12 22 5 15 3 12 15 3 11";

assert(result === expectations); // undefined (meaning OK)