[jQuery] table striping - skip hidden rows

[rolfsf]

I have a table with multiple tbody's. Within each tbody there are a
number of rows that can be hidden or shown by clicking on a link. I'm
using the following function to stripe alternating rows:

        jQuery.fn.stripeTable = function(){
                        $(this).find("tbody 
tr:nth-child(even)").addClass("alt");
        }

but now I'm trying to account for hidden rows, so that when I click to
hide some rows I the striping is revised

I can't quite work out the syntax to filter first for visible rows,
then find even rows among those

can anyone assist?