Title Case a Sentence (why my code not passing tests)

Tell us what’s happening:
I am solving the following challenge:
Return the provided string with the first letter of each word capitalized. Make sure the rest of the word is in lower case.

Why my code is not passing the tests?
Using console.log() shows the correct expected outcome. I have also run it in another online Javascript compiler and it works there as well.

Your code so far

function titleCase(str) {
let arr = str.split(' ');
let s = '';
for (let i = 0; i < arr.length ; i++){
  s += arr[i].charAt(0).toUpperCase() + arr[i].slice(1).toLowerCase() + ' ';      
return s;

titleCase("I'm a little tea pot");

Your browser information:

User Agent is: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/85.0.4183.102 Safari/537.36.

Challenge: Title Case a Sentence

Link to the challenge:

You add a space character after every word you append to s with the + ' ' part of this line. So instead of returning "I'm A Little Tea Pot", you return "I'm A Little Tea Pot "


Thank you very much!