Write a function that takes an input sentence, and mixes up the insides of words (anything longer than 3 letters)

scramble.ts

const scrambleLetters = (letters: string) =>
  letters
    .split('')
    .sort(() => Math.random() - 0.5)
    .join('')

const scramble = (str: string) =>
  str
    .split(' ')
    .map(word => (word.length > 3 ? `${word[0]}${scrambleLetters(word.slice(1, word.length - 1))}${word[word.length - 1]}` : word))
    .join(' ')