find-the-missing-letter.js

// Find the missing letter
// Write a method that takes an array of consecutive (increasing) letters as input and that returns the missing letter in the array.

// You will always get an valid array. And it will be always exactly one letter be missing. The length of the array will always be at least 2.
// The array will always contain letters in only one case.

// Example:

// ['a','b','c','d','f'] -> 'e'
// ['O','Q','R','S'] -> 'P'
// (Use the English alphabet with 26 letters!)

// Have fun coding it and please don't forget to vote and rank this kata! :-)

// I have also created other katas. Take a look if you enjoyed this kata!

// solution

function findMissingLetter(array) {
  let checkArray = [
    "a",
    "b",
    "c",
    "d",
    "e",
    "f",
    "g",
    "h",
    "i",
    "j",
    "k",
    "l",
    "m",
    "n",
    "o",
    "p",
    "q",
    "r",
    "s",
    "t",
    "u",
    "v",
    "w",
    "x",
    "y",
    "z",
    "A",
    "B",
    "C",
    "D",
    "E",
    "F",
    "G",
    "H",
    "I",
    "J",
    "K",
    "L",
    "M",
    "N",
    "O",
    "P",
    "Q",
    "R",
    "S",
    "T",
    "U",
    "V",
    "W",
    "X",
    "Y",
    "Z",
  ];
  let startPoint = checkArray.slice(checkArray.indexOf(array[0]));
  return startPoint.filter((char) => !array.includes(char))[0];
}