vue implements a simple virtual list

Long list:
In front-end development, you will encounter some data that are large in size and cannot be loaded using paging. This kind of list is called 长列表.
It is basically difficult to meet business requirements for a fully rendered long list. There are generally two ways to create a non-completely rendered long list:

懒渲染: This is a common wireless scrolling method. Only a part (such as 10 items) is rendered at a time. When the remaining part scrolls to the visible area, another part is rendered.
可视区域渲染: Only the visible parts are rendered, and the invisible parts are not rendered.

虚拟列表就是采用的可视区渲染方式优化

Idea reference:

<template>
  <!-- 虚拟列表容器，类似“窗口”，窗口的高度取决于一次展示几条数据
            比如窗口只能看到10条数据，一条40像素，10条400像素
            故，窗口的高度为400像素，注意要开定位和滚动条 -->
  <div
    class="virtualListWrap"
    ref="virtualListWrap"
    @scroll="handleScroll"
    :style="{ height: itemHeight * count + 'px' }"
  >
    <!-- 占位dom元素，其高度为所有的数据的总高度 -->
    <div
      class="placeholderDom"
      :style="{ height: allListData.length * itemHeight + 'px' }"
    ></div>
    <!-- 内容区，展示10条数据，注意其定位的top值是变化的 -->
    <div class="contentList" :style="{ top: topVal }">
      <!-- 每一条（项）数据 -->
      <div
        v-for="(item, index) in showListData"
        :key="index"
        class="itemClass"
        :style="{ height: itemHeight + 'px' }"
      >
        {
   
   { item.name }}
      </div>
    </div>
    <!-- 加载中部分 -->
    <div class="loadingBox" v-show="loading">
      <i class="el-icon-loading"></i>
      &nbsp;&nbsp;<span>loading...</span>
    </div>
  </div>
</template>
<script>
import axios from "axios";
export default {
  data() {
    return {
      allListData: [], // 所有的数据，比如这个数组存放了十万条数据
      itemHeight: 40, // 每一条（项）的高度，比如40像素
      count: 10, // 一屏展示几条数据
      start: 0, // 开始位置的索引
      end: 10, // 结束位置的索引
      topVal: 0, // 父元素滚动条滚动，更改子元素对应top定位的值，确保联动
      loading: false,
    };
  },
  computed: {
    // 从所有的数据allListData中截取需要展示的数据showListData
    showListData: function () {
      return this.allListData.slice(this.start, this.end);
    },
  },
  async created() {
    this.loading = true;
    const res = await axios.get("http://ashuai.work:10000/bigData");
    this.allListData = res.data.data;
    this.loading = false;
  },
  methods: {
    // 滚动这里可以加上节流，减少触发频次
    handleScroll() {
      /**
       * 获取在垂直方向上，滚动条滚动了多少像素距离Element.scrollTop
       *
       * 滚动的距离除以每一项的高度，即为滚动到了多少项，当然，要取个整数
       * 例：滚动4米，一步长0.8米，滚动到第几步，4/0.8 = 第5步（取整好计算）
       *
       * 又因为我们一次要展示10项，所以知道了起始位置项，再加上结束位置项，
       * 就能得出区间了【起始位置, 起始位置 + size项数】==【起始位置, 结束位置】
       * */
      const scrollTop = this.$refs.virtualListWrap.scrollTop;
      this.start = Math.floor(scrollTop / this.itemHeight);
      this.end = this.start + this.count;
      /**
       * 动态更改定位的top值，确保联动，动态展示相应内容
       * */
      this.topVal = this.$refs.virtualListWrap.scrollTop + "px";
    },
  },
};
</script>
<style scoped lang="less">
// 虚拟列表容器盒子
.virtualListWrap {
  box-sizing: border-box;
  width: 240px;
  border: solid 1px #000000;
  // 开启滚动条
  overflow-y: auto;
  // 开启相对定位
  position: relative;
  .contentList {
    width: 100%;
    height: auto;
    // 搭配使用绝对定位
    position: absolute;
    top: 0;
    left: 0;
    .itemClass {
      box-sizing: border-box;
      width: 100%;
      height: 40px;
      line-height: 40px;
      text-align: center;
    }
    // 奇偶行改一个颜色
    .itemClass:nth-child(even) {
      background: #c7edcc;
    }
    .itemClass:nth-child(odd) {
      background: pink;
    }
  }
  .loadingBox {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(255, 255, 255, 0.64);
    color: green;
    display: flex;
    justify-content: center;
    align-items: center;
  }
}
</style>

Reference: 8 ways to cleverly deal with the backend returning 100,000 pieces of data at once

Virtual list and its principle_What is a virtual list_illion-78's blog-CSDN blog

vue implements a simple virtual list

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