Узнайте JavaScriptWhale Talk

input = "You Are All Wee Gillis";
vowels = ['a','e','i','o','u'];
whaleTalk = [];
input.split('').filter(v => vowels.includes(v.toLowerCase())).forEach(x => {
  if (x === 'e' || x === 'u') {
    whaleTalk.push((x + x));
  } else {
    whaleTalk.push(x);
  }
});
console.log(whaleTalk.join('').toUpperCase())    //  OUUAEEAEEEEII
Naughty Narwhal