无边距视口中可见的Javascript元素

实际JS:

(function ($) {
        $.fn.visible = function (partial) {

            var $t = $(this),
                $w = $(window),
                viewTop = $w.scrollTop(),
                viewBottom = viewTop + $w.height(),
                _top = $t.offset().top,
                _bottom = _top + $t.height(),
                compareTop = partial === true ? _bottom : _top,
                compareBottom = partial === true ? _top : _bottom;

            return compareBottom <= viewBottom && compareTop >= viewTop;
        };
    })(jQuery);

    var win = $(window);

    var allModifications = $(".animation-listener");

    //make all elements visible that are directly visible
    allModifications.each(function (i, el) {
        console.log("loaded js");
        var el = $(el);
        if (el.visible(true)) {
            el.find(".half-width-text").addClass("open");
        }
    });

    //make elements visible that get scrolled into the viewport
    win.scroll(function (event) {
        var current = 1;
        allModifications.each(function (i, el) {
            var el = $(el);
            if (el.visible(true)) {
                el.addClass("animate");
            }
        });
    });