wxml：

<image class="go_top" src="../../images/gotop.png" hidden="{{!go_top_show}}" bindtap="goTop"></image>

wxss:

/* 回到頂部 */
.go_top{
  width: 80rpx;
  height: 80rpx;
  position: fixed;
  bottom: 50rpx;
  right: 30rpx;
  text-align: center;
  box-sizing: border-box;
  border-radius: 50%;
}

js:

  data: {
    go_top_show: false
  },

  // 獲取滾動條當前位置
  height="580" src="https://img-blog.csdnimg.cn/2020092417275416.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQwMTQ2Nzg5,size_16,color_FFFFFF,t_70" width="328" />
 
 
 
參考：https://blog.csdn.net/sxs1995/article/details/80091924