Check if an element in DOM is in viewable area

is-in-view.js

/* Requires jQuery */
function isInView(el) {
	var docViewTop = $(window).scrollTop();
	var docViewBtm = docViewTop + $(window).height();
	var elTop = $(el).offset().top;
	var elBtm = elTop + $(el).height();
	return ((elBtm <= docViewBtm) && (elTop >= docViewTop));
}