网页右下角返回顶部js插件back2top

const button = document.querySelector("#back2top");
BACK2TOP(button, 200);

button#back2top{
  position: fixed;
  right: 2%;
  bottom: 2%;
  opacity: 0;
  visibility: hidden;
  font-size: 14px;
  color: #fff;
  background-color: #4F46E5;
  border: none;
  outline: none;
  cursor: pointer;
  padding: 10px 18px;
  margin: 0;
  border-radius: 3px;
}