JAVASCRIPT

javascript convert number to spreadsheet column

/**
 * Convert a whole number that is more than zero to a spreadsheet column letters. eg. 1 -> A
 * Source: https://stackoverflow.com/questions/45787459/convert-number-to-alphabet-string-javascript/45787487
 * 
 * @param {Number} num - (required) The number to convert to a spreadsheet column letter. Must be greater than zero.
 *
 * @returns {(String|undefined)} The spreadsheet column letter or undefined.
 */
function numToSSColumnLetter(num) {
  let columnLetter = "",
    t;

  while (num > 0) {
    t = (num - 1) % 26;
    columnLetter = String.fromCharCode(65 + t) + columnLetter;
    num = (num - t) / 26 | 0;
  }
  return columnLetter || undefined;
}

numToSSColumn(0); // undefined
numToSSColumn(1); // A
numToSSColumn(26); // Z
numToSSColumn(-1); // undefined
numToSSColumn(27); // AA
numToSSColumn(475254); // ZZZZ