[jQuery] looping through elements with jQuery based on class

[led]

I'm try to use star rating plugin frm http://fyneworks.com/jquery/star-rating/.

I need to add class 'star-rating-on' on the divs  with class 'star-
rating rater-0 auto-submit-star star-rating-applied star-rating-
live' .

I can use:

$("div.star-rating rater-0 auto-submit-star star-rating-applied star-
rating-live").each(function(){
                                        $(this).addClass('star-rating-
on')
                                });
but it isn't working.

and also i need to do it on first X elements in page.

thanks in advance.