gistfile1.txt

       // http://stackoverflow.com/questions/21474678/scrolltop-animation-without-jquery
        function scrollToTop() {
            var deferred = $q.defer();

            var content = document.getElementById('content');

            var scrollDuration = 1200 * ((content.scrollTop / content.offsetHeight));

            var cosParameter = content.scrollTop / 2,
                scrollCount = 0,
                oldTimestamp = performance.now();

            function step (newTimestamp) {
                scrollCount += Math.PI / (scrollDuration / (newTimestamp - oldTimestamp));
                if (scrollCount >= Math.PI) content.scrollTop = 0;
                if (content.scrollTop === 0) {
                    deferred.resolve();
                } else {
                    content.scrollTop =Math.round(cosParameter + cosParameter * Math.cos(scrollCount));
                    oldTimestamp = newTimestamp;
                    window.requestAnimationFrame(step);
                }
            }
            window.requestAnimationFrame(step);

            return deferred.promise;
        }