/**
 * Check if DOM element is in browsers view port
 * @param el The element
 * @return boolean
 */
function isInViewport(el) {
    var rect = el.getBoundingClientRect();

    return (
        rect.bottom >= 0 &&
        rect.right >= 0 &&

        rect.top <= (
            window.innerHeight ||
            document.documentElement.clientHeight) &&

        rect.left <= (
            window.innerWidth ||
            document.documentElement.clientWidth)
    );
}