Vue小技能

1.回到顶部

<template>
  <div class="homes">
    <!-- 回顶部按钮为一张50*50的图片 -->
    <!-- btnFlag 控制图片显示隐藏 -->
    <!-- backTop 回顶部的方法 -->
    <img
      v-if="btnFlag"
      class="go-top"
      src="https://img03.sogoucdn.com/app/a/201025/b57f8208c4a3274b63d6a9108bc33573"
      @click="backTop"
    />
  </div>
</template>
<script>
export default {
  data() {
    return {
      btnFlag: false,
      scrollTop: 0,
    };
  },
  // vue的两个生命钩子，这里不多解释。
  // window对象，所有浏览器都支持window对象。它表示浏览器窗口，监听滚动事件
  mounted() {
    window.addEventListener("scroll", this.scrollToTop);
  },
  destroyed() {
    window.removeEventListener("scroll", this.scrollToTop);
  },

  methods: {
    // 点击图片回到顶部方法，加计时器是为了过渡顺滑
    backTop() {
      const that = this;
      let timer = setInterval(() => {
        let ispeed = Math.floor(-that.scrollTop / 5);
        document.documentElement.scrollTop = document.body.scrollTop =
          that.scrollTop + ispeed;
        if (that.scrollTop === 0) {
          clearInterval(timer);
        }
      }, 16);
    },

    // 为了计算距离顶部的高度，当高度大于60显示回顶部图标，小于60则隐藏
    scrollToTop() {
      const that = this;
      let scrollTop =
        window.pageYOffset ||
        document.documentElement.scrollTop ||
        document.body.scrollTop;
      that.scrollTop = scrollTop;
      if (that.scrollTop > 60) {
        that.btnFlag = true;
      } else {
        that.btnFlag = false;
      }
    },
  },
};
</script>

<style>
.homes {
  width: 100%;
  height: 1000px;
  border: 2px solid red;
}
.go-top {
  width: 50px;
  height: 50px;
}
</style>