Array and String reverse with recursion

index.js

function reverse(/**@type {string}*/ word, index = word.length) {
  let newPos = word.length - index;
  let letters = word.split("");
  let tempLetter = word[newPos];

  letters[newPos] = word[index - 1];
  letters[index - 1] = tempLetter;
  if (Math.round(word.length / 2) === index) return word;
  return reverse(letters.join(""), index - 1);
}

function reverseArray(/**@type {Array}*/ arr, index = arr.length) {
  let newPos = arr.length - index;
  let tempElement = arr[newPos];
  arr[newPos] = arr[index - 1];
  arr[index - 1] = tempElement;
  if (Math.round(arr.length / 2) === index) return arr;
  return reverseArray(arr, index - 1);
}

console.log(reverseArray([1,2,3,4,5]));
function reverse2(word, index) {
  if (!index) {
    return reverse(word, word.length - 1);
  } else if (index <= (word.length - 1) / 2) {
    return word;
  } else {
    let letters = word.split("");
    let startIndex = word.length - 1 - index;
    let temp = letters[index];
    letters[index] = letters[startIndex];
    letters[startIndex] = temp;
    return reverse(letters.join(""), index - 1);
  }
}
function assertString(/**@type {string}*/ word) {
  let native = word
    .split("")
    .reverse()
    .join("");
  let mine = reverse(word);
  return native === mine;
}