[removed] How to detect if browser window is scrolled to bottom?

Question

I need to detect if a user is scrolled to the bottom of a page. If they are at the bottom of the page, when I add new content to the bottom, I will automatically scroll them

Answer 1

I was searching for an answer but haven't found an exact one. Here is a pure javascript solution that works with latest Firefox, IE and Chrome at the time of this answer:

// document.body.scrollTop alone should do the job but that actually works only in case of Chrome.
// With IE and Firefox it also works sometimes (seemingly with very simple pages where you have
// only a 
 or something like that) but I don't know when. This hack seems to work always.
var scrollTop = (document.documentElement && document.documentElement.scrollTop) || document.body.scrollTop;

// Grodriguez's fix for scrollHeight:
// accounting for cases where html/body are set to height:100%
var scrollHeight = (document.documentElement && document.documentElement.scrollHeight) || document.body.scrollHeight;

// >= is needed because if the horizontal scrollbar is visible then window.innerHeight includes
// it and in that case the left side of the equation is somewhat greater.
var scrolledToBottom = (scrollTop + window.innerHeight) >= scrollHeight;

// As a bonus: how to scroll to the bottom programmatically by keeping the horizontal scrollpos:
// Since window.innerHeight includes the height of the horizontal scrollbar when it is visible
// the correct vertical scrollTop would be
// scrollHeight-window.innerHeight+sizeof(horizontal_scrollbar)
// Since we don't know the visibility/size of the horizontal scrollbar
// we scroll to scrollHeight that exceeds the value of the
// desired scrollTop but it seems to scroll to the bottom with all browsers
// without problems even when the horizontal scrollbar is visible.
var scrollLeft = (document.documentElement && document.documentElement.scrollLeft) || document.body.scrollLeft;
window.scrollTo(scrollLeft, scrollHeight);