Scroll Depth Indicator

jQuery(function($) {

    $( document ).ready(function() {
        if ($('.animatedCounter').length) {
            $(window).scroll(testScroll);
        }
    });
    var viewed = false;

    function isScrolledIntoView(elem) {
        var docViewTop = $(window).scrollTop();
        var docViewBottom = docViewTop + $(window).height();

        var elemTop = $(elem).offset().top;
        var elemBottom = elemTop + $(elem).height();

        return ((elemBottom <= docViewBottom) && (elemTop >= docViewTop));
    }

    function testScroll() {
        if (isScrolledIntoView($(".animatedCounter")) && !viewed) {
            viewed = true;
            $('.animatedCounter').each(function () {
                $(this).prop('Counter',0).animate({
                    Counter: $(this).text()
                }, {
                    duration: 1000,
                    easing: 'swing',
                    step: function (now) {
                        $(this).text(Math.ceil(now));
                    }
                });
            });
        }
    }
}(jQuery));

Source