Javascript String spinWords(string)

function spinWords(string){
  var res = '';
  var words = string.split(" ");
  
  for(var i = 0; i < words.length; i ++) {
    res += (words[i].length >= 5) ? words[i].reverse() : words[i];
    res += ' ';/*from   w w w. j  a  v  a2 s . com*/
  }
  
  return res.substring(0, res.length - 1);
}

String.prototype.reverse = function () { return this.split("").reverse().join(""); };