selecting li elements

selecting li elements

I use the following selector to perform something on each element:
$('div,article,aside,footer,header,main,nav,section,summery,h1,h2,h3,ul,ol,il,a,p').each(function(){
.... 
       this_type  = $(this).prev().prop('nodeName');
        if (typeof this_tpe != 'undefined' ){   
        if (this_type == 'IL' )
          alert(this_type );
        }
.............
.............
 

Problem is that I can't get some of the element types, like 'li'.

Am I being mistaken or what:
Regards
I. Sher