what type or types of input should reverse take in javascript code example

Example 1: javascript reverse string

function reverseString(str) {
    return str.split("").reverse().join("");
}
reverseString("hello");

Example 2: reverse a word javascript

function reverseWords(str) {
  const allWords = str.split(" ")
  return allWords.map(item => item.split("").reverse().join("")).join(" ")
}