纯原生js返回顶部效果

实现代码如下：

const scrollToptimer = () => {
      let scrollToptimer = setInterval(function () {
        var top = document.body.scrollTop || document.documentElement.scrollTop;
        var speed = top / 4;
        if (document.body.scrollTop != 0) {
          document.body.scrollTop -= speed;
        } else {
          document.documentElement.scrollTop -= speed;
        }
        if (top == 0) {
          clearInterval(scrollToptimer);
        }
      }, 30);
    };