无法让横幅向下滚动

.banner {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 50px;
  background-color: #f1f1f1;
  overflow: hidden;
}

function scrollBanner() {
  var banner = document.querySelector('.banner');
  var scrollHeight = banner.scrollHeight;
  var scrollTop = banner.scrollTop;
  
  if (scrollTop < scrollHeight) {
    banner.scrollTop += 1; // 每次滚动的距离
  } else {
    banner.scrollTop = 0; // 滚动到顶部重新开始
  }
}

setInterval(scrollBanner, 50); // 每隔一段时间执行一次滚动