判断页面的滚动方向

判断页面的滚动方向

    $(window).scroll(function(){
        var before = $(window).scrollTop();
        $(window).scroll(function() {
            var after = $(window).scrollTop();
                 if (before<after) {
                     console.log("向下")
                     before = after;
                 };
                 if (before>after) {
                   console.log("向上")
                     before = after;
                 };
           
        });
    });