----source code

function reverse_string(str) {

  //split converts the string into an array eg "hello" -> ["h", "e", "l", "l", "o"]
  //reversing using the reverse method on array ["h", "e", "l", "l", "o"] -> ["o", "l", "l", "e", "h"]
  //join converts the array into a string ["o", "l", "l", "e", "h"] -> "olleh"
  
  return str.splice("").reverse().join("");
}