Writing function that returns string but with all five or more letters reversed JS

Question

first time posting. I'm writing a function in js that reverses words with more than 5 characters in a given string. It works, but I think it is adding extra "space" strings that it doesn't need if the string inputted is only one word. I know I have too many variables and there is a way better way to do this. I'm pretty new to this, but anything helps. Thanks!

const exString = "Hey fellow warriors"
function spinWords(string){
    let newWord = string.split(' ');
    let fiveWord = "";
    let lessWord = "";
    for(i=0; i<newWord.length;i++){
        if(newWord[i].length >=5){
            fiveWord += newWord[i].split('').reverse() + ' ';
            }
        else{
            lessWord += newWord[i]
            }        
    }
    newFiveWord = fiveWord.replace(/,/g,'');
    return lessWord + ' ' + newFiveWord     
}
console.log(spinWords(exString));

Answer 1

const spinWords = str => str
  .split(' ')
  .map(word => word.length >= 5
    ? [...word].reverse().join('')
    : word)
  .join(' ')
  
console.log(spinWords("Hey fellow warriors"))

1. Turn the string into an array of words
2. Modify each word. If 5+ letters: [..word] turns the string into an array of letters ('hi' > ['h', 'i']). Then reverse the array, and turn the letters back into one string.
3. Undo step one by turning the array into one string.