toPigLatin.ts

const isVowel = (c: string) => 'aeiouy'.includes(c)
const yay = (word: string) => word + (isVowel(word[word.length - 1]) ? 'y' : '') + 'ay'
const isUpperString = (c: string) => c === c.toUpperCase()
const hasUpperCharacter = (word: string) => word.split('').find(isUpperString)

const restablishCase = (word: string) => hasUpperCharacter(word)
	? word[0].toUpperCase() + word.substring(1).toLowerCase()
	: word;

const toPigLatinWord = (word: string) => {
	const index = word.split('').findIndex(isVowel)
	return restablishCase(yay(word.substring(index) + word.substring(0, index)))
}


const toPigLatinSentence = (sentence: string) => sentence.replace(/\w+/g, toPigLatinWord)

console.log(toPigLatinSentence('Come to the dark side, we have cookies (and keebs!)'))
// Omecay otay ethay arkday idesay, eway avehay ookiescay (anday eebskay!)