返回顶部

window.onscroll = function () {
    if (document.body.scrollTop || document.documentElement.scrollTop > 0) {
        document.getElementById('back_top').style.display = "block";
    } else {
        document.getElementById('back_top').style.display = "none";
    }
}
$('.back_top').click(function () {
    $("html,body").animate({ scrollTop: 0 }, 500);
    return false;
});