jquery nth child that is currently visible

I can style every 4th 'item' div like so jQuery(".item:nth-child(4n)").addClass("fourth-item"); and that works fine, but then I hide some items, show some others and want to re-do this styling, but only styling every 4th item that is visible. So I have a function that will remove this styling and reapply it, but I need to specify in the reapplying of the style that it is only every 4th visible ite