Search and Replace

Tell us what’s happening:
guys you can see whats happening why is it not running correctly??
please help!!

Your code so far

function myReplace(str, before, after) {
  str=str.split(" ");
  for(var i=0;i<str.length;i++){
  return str.join(" ");

myReplace("He is Sleeping on the couch", "Sleeping", "sitting");

Your browser information:

Your Browser User Agent is: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_7_4) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/49.0.2623.112 Safari/537.36.

Link to the challenge:

You forgot to preserve capitalization. If the word you’re going to replaced is capitalized, you should capitalize the replacement word as well.