How to create a script to split and rejoin words in Google Sheets?

Question

I am trying to write an Apps Script script in Google Sheets to split a cell containing words and re concatenate them in a different format. There may be any number of words in the input cell.

Input in cell A1: cat, dog, mouse, rat

Output in cell B2 : "CAT", "DOG", "MOUSE", "RAT"

I cannot get the for loop correct

function tags(data) {
  array1 = data.split(", ");
  a =[]
  for (i=1; i<21; i++){
    a = a + char(34) + i + char(34)
    return a
  }
}

Answer 1

function tags(data) {
  data = data.toUpperCase().split(",");

  for (var i = 0; i < data.length; i++)
    data[i] = ('"' + data[i] + '"');
  
  return data.join(", ");
}