j is what number in the alphabet code example

Example: javascript number in alphabet

// converts numbers to spreadsheet letter columns eg. 1 -> A
function numToSSColumn(num){
  let s = '', t;

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

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