动画jQuery scrolltop

$('html, body').animate({scrollTop: 0}, 'slow');

.scroll-top {
  transition: transform 0.5s ease-in-out;
  transform: translateY(-100%);
}

window.addEventListener('scroll', function() {
  var scrollTop = document.documentElement.scrollTop || document.body.scrollTop;
  var scrollTopElement = document.getElementById('scroll-top');
  if (scrollTop > 200) {
    scrollTopElement.classList.add('scroll-top');
  } else {
    scrollTopElement.classList.remove('scroll-top');
  }
});