How To Identify Name/id Of Named Anchor?

I use named anchors to take users to specific parts of a long page. But I
want to add some processing and do some things with my nav bar when users go
to certain sections delineated by named anchors. I understand that the
anchors array creates an element for each anchor in the page when the page
is loaded, but how do I identify which anchor is currently being viewed?

Here's some pseudo code:

if (document.anchors.name == "section_B") {

then do this or that

}

But what do I test to determine the current anchor name?

What about using id's instead of names? Can the anchors array return
anchors created with id's as well as names? Would this be of any benefit?