Nice use of a for loop right there!
Another method of doing this 'reversig' came to mind, you may want to consider using here.
You take the string and use Array.split('') to create an array containing the string's chars.
Arrays have an Array.reverse() function which does the same as your for loop.
Restore the string by using Array.join('') to fuse the array into a string.
To be honest, I'm not sure if doing it this way would save resources, but I believe that it looks for readable and hence, has better maintainability.