May seem odd to check if the page scroll is at bottom, but can be useful if you need to hide something or show something else, as in a back to top button for example.

$('#back-to-top').hide();
$(window).scroll(function(){
    if ( document.body.scrollHeight - $(this).scrollTop()  <= $(this).height() ){
        $('#back-to-top').show();
    } else {
        $('#back-to-top').hide();
    }
});