I can't figure out how to check with jquery how deep a user has
scrolled into a page. Suppose you got a webpage with 3000px in height
but the actual viewport is just 768px high. So the user has to scroll
down to see the rest of the page. How do i get the current vertical
scroll value of the page. So for instance if the user is at the bottom
of the page the scroll value should then be 2232px since the
viewport's top is at this position. So the function i'm looking for
should give me the top offset of the viewport position. But I don't
know which function this should be. I tried "$('body').scrollTop();"
but it always returns 0.
