html代码

  <a-icon
      type="vertical-align-top"
      class="top"
      name="back-top"
      @click="backTop"
      v-if="btnFlag"
    />

css代码

.top {
  height: 35px;
  width: 37px;
  position: fixed;
  right: 5%;
  bottom: 5%;
  text-align: center;
  line-height: 45px;
  font-size: 20px;
  background-color: #fff;
  border-radius: 50%;
  box-shadow: 0px 1px 3px 1px #888888;
  z-index: 999;
}

返回顶部

    backTop() {
      const timer = setInterval(() => {
        let scrollTop = document.getElementsByClassName("wk-layout_body")[0].scrollTop;
        let ispeed = Math.floor(-scrollTop / 5);
        document.getElementsByClassName("wk-layout_body")[0].scrollTop = scrollTop + ispeed;
        if (scrollTop === 0) {
          clearInterval(timer);
        }
      });
    },

显示/隐藏返回标志

data() {
    return {
   btnFlag: false,
   }
 },
   
 mounted() {
    window.addEventListener("scroll", this.scrollToTop, true);
  },
  destroyed() {
    window.removeEventListener("scroll", this.scrollToTop);
  },
  scrollToTop() {
      let elVal = document.getElementsByClassName("wk-layout_body")[0];
      let windowHeight = elVal.offsetHeight / 2;
      const that = this;
      that.scrollTop = elVal.scrollTop;
      if (that.scrollTop > windowHeight) {
        that.btnFlag = true;
      } else {
        that.btnFlag = false;
      }
    },