Mouse scroll to change the progress of the navigation bar

Why 80% of the code can not do farming architect? >>>  

Official website

Scroll event

function scrollBar() {
    if (document.body.clientWidth > 860) {
        $(window).scroll(function () {
            var s = $(window).scrollTop();
            var a = $(document).height();
            var b = $(window).height();
            var result = parseInt(s / (a - b) * 100);
            $("#bar").css("width", result + "%");
            if (false) {
                if (result >= 0 && result <= 19)
                    $("#bar").css("background", "#cccccc");
                if (result >= 20 && result <= 39)
                    $("#bar").css("background", "#50bcb6");
                if (result >= 40 && result <= 59)
                    $("#bar").css("background", "#85c440");
                if (result >= 60 && result <= 79)
                    $("#bar").css("background", "#f2b63c");
                if (result >= 80 && result <= 99)
                    $("#bar").css("background", "#FF0000");
                if (result == 100)
                    $("#bar").css("background", "#5aaadb");
            } else {
                $("#bar").css("background", "orange");
            }
            $(".toc-container").css("height", $(".site-content").outerHeight());
            $(".skin-menu").removeClass('show');
        });
    }
}

 

Reproduced in: https: //my.oschina.net/lemos/blog/3057158