letterFromNumber.js

function letterFromNumber = function( number ) {
  var letter = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'.charAt(number % 26)
  var concat = Math.round(number / 26);
  return concat > 0 ? letterFromNumber(concat-1) + letter : letter;
};

function letterFromNumber (number) {
var letter = 'abcdefghijklmnopqrstuvwxyz'.charAt(number % 26);
var concat = Math.floor(number / 26);
return concat > 0 ? letterFromNumber(concat-1) + letter : letter;
};

little fix

Fixed, thanks @Yakubko

Thanks Sir. Very useful

https://www.geeksforgeeks.org/find-excel-column-name-given-number/