jQuery check if element is scrolled to (close to Bootstrap affix)

scroll.js

window.page_var = {};
window.onload = function() {
	$(".b_screens__el").each(function (i) {
		page_var.screens[i] = $(this).offset().top;
	})
}
$(window).resize(function() {
	$(".b_screens__el").each(function (i) {
		page_var.screens[i] = $(this).offset().top;
	})
});

$(window).scroll(function(e) {
	page_var.s_t = $(window).scrollTop();

	for(var i = 0; i < page_var.screens_c; i++) {
		if (page_var.s_t >= page_var.screens[i]) {
			if (i != page_var.screens_c+1 && page_var.s_t < page_var.screens[i+1]) {
				page_var.active_screen = i;

				$(".b_menu.m_main .list > li")
					.eq(i).addClass("active")
					.siblings().removeClass("active");
				$("#container").attr("data-active-screen", page_var.active_screen)
			} else if (i != page_var.screens_c+1 && page_var.s_t > page_var.screens[i+1]) {
				continue;
			} else {
				page_var.active_screen = i;

				$(".b_menu.m_main .list > li")
					.eq(i).addClass("active")
					.siblings().removeClass("active");
				$("#container").attr("data-active-screen", page_var.active_screen)
			}
		}
	}



	// scroll
});