Fixing things to the top of a foot.
Styles should go from fixed to absolute
$(window).on({
scroll : function () {
let footerTop = $footer.offset().top;
let windowBottom = $window.scrollTop() + $window.height();
if (windowBottom >= footerTop) {
$backToTop.addClass('is-stuck');
}
else if (footerTop > windowBottom) {
$backToTop.removeClass('is-stuck');
}
},
});