用vue实现虚拟列表

把以下代码拷贝放到html文件中即可查看效果
vue.js 文件需要自己引入

<!doctype html>
<html lang="zh">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>虚拟列表</title>
  <style>
    .container {
      width: 300px;
      height: 370px;
      overflow: auto;
      border: 1px solid;
      margin: 100px auto;
    }

    .item {
      height: 39px;
      line-height: 30px;
      border-bottom: 1px solid #aaa;
      padding-left: 20px;
    }
  </style>
</head>

<body>
  <div id="app">
    <button @click="add">增加</button>
    <div class="container" ref="container">
      <div class="scroll-wrapper" :style="style">
        <div v-for="(item, index) in scrollList" :key="index" class="item">{{item}}</div>
      </div>
    </div>
  </div>
  <!-- vue自行引入 -->
  <script src="../vue.js"></script>
  <script>
    new Vue({
      el: '#app',
      data: {
        list: [],
        itemLen: 40, //每一项高度
        startIndex: 0,
        endIndex: 0,
        paddingTop: 0,
        paddingBottom: 0,
        allHeight: 0, //所有数据的高度
      },
      computed: {
        scrollList() {
          //截取要展示的数据
          return this.list.slice(this.startIndex, this.endIndex)
        },
        style() {
          //获取内容体的上下padding
          return {
            paddingTop: this.paddingTop + 'px',
            paddingBottom: this.paddingBottom + 'px'
          }
        }
      },
      mounted() {
        const needLen = Math.ceil(370 / this.itemLen) + 1;
        this.endIndex = needLen;
        this.add();
        const container = this.$refs.container;
        this.timer = null;
        //利用外层div的高度 和 每一项的高度，获取可视区域需要展示的数据条数
        container.addEventListener('scroll', () => {
          //防抖
          if (this.timer) {
            clearTimeout(this.timer);
          }
          this.timer = setTimeout(() => {
            const top = container.scrollTop;
            console.log(top);
            //当列表滚动到任何一个位置，利用滚动条距离顶部的值算出需要展示数据的起止位置
            this.startIndex = Math.floor(top / this.itemLen)
            this.endIndex = this.startIndex + needLen;

            //重新设置上下边距
            this.paddingTop = this.startIndex * this.itemLen;
            if (this.list.length >= this.endIndex) {
              this.paddingBottom = (this.list.length - this.endIndex) * this.itemLen;
            } else {
              this.paddingBottom = 0;
            }
          }, 20);
        })
      },
      methods: {
        add() {
          let arr = new Array(30).fill(0)
          let basis = this.list.length;
          arr = arr.map((item, index) => {
            return index + 1 + basis
          })
          this.list = [
            ...this.list,
            ...arr
          ];
          //插入数据，重新设置下边距
          const valLen = this.list.length
          this.allHeight = valLen * this.itemLen
          this.paddingBottom = this.allHeight - this.endIndex * this.itemLen
        }
      }
    })
  </script>
</body>

</html>