need elem to appear only if falls beyond viewport.....

need elem to appear only if falls beyond viewport.....

hi,

I have a "back to top" link at the bottom of my pages, but I'd like this cta to appear only if it falls below the visible part of the page (i.e., beyond the viewport... in the scrolling area, I think it's also referred to..)

is there a way to do this with jQuery?

thank you...