const isVowel = (l) => (r = l == "A" || l == "E" || l == "I" || l == "O" || l == "U");

const vowelDoubler = (arr) => {
  for(var i = 0; i < arr.length; i++) {
    if (isVowel(arr[i].toUpperCase())){
      arr.splice(i, 0, arr[i]);
      i++
    }
  }
  return arr
}