虚拟列表

<template>
  <div ref="list" class="infinite-list-container" @scroll="scrollEvent($event)">
    <div class="infinite-list-phantom" :style="{ height: listHeight + 'px' }"></div>
    <div class="infinite-list" :style="{ transform: getTransform }">
      <div ref="items"
        class="infinite-list-item"
        v-for="item in visibleData"
        :key="item.id"
        :style="{ height: itemSize + 'px',lineHeight: itemSize + 'px' }"
      >{{ item.value }}</div>
    </div>
  </div>
</template>

export default {
  name:'VirtualList',
  props: {
    //所有列表数据
    listData:{
      type:Array,
      default:()=>[]
    },
    //每项高度
    itemSize: {
      type: Number,
      default:200
    }
  },
  computed:{
    //列表总高度
    listHeight(){
      return this.listData.length * this.itemSize;
    },
    //可显示的列表项数
    visibleCount(){
      return Math.ceil(this.screenHeight / this.itemSize)
    },
    //偏移量对应的style
    getTransform(){
      return `translate3d(0,${this.startOffset}px,0)`;
    },
    //获取真实显示列表数据
    visibleData(){
      return this.listData.slice(this.start, Math.min(this.end,this.listData.length));
    }
  },
  mounted() {
    this.screenHeight = this.$el.clientHeight;
    this.start = 0;
    this.end = this.start + this.visibleCount;
  },
  data() {
    return {
      //可视区域高度
      screenHeight:0,
      //偏移量
      startOffset:0,
      //起始索引
      start:0,
      //结束索引
      end:null,
    };
  },
  methods: {
    scrollEvent() {
      //当前滚动位置
      let scrollTop = this.$refs.list.scrollTop;
      //此时的开始索引
      this.start = Math.floor(scrollTop / this.itemSize);
      //此时的结束索引
      this.end = this.start + this.visibleCount;
      //此时的偏移量
      this.startOffset = scrollTop - (scrollTop % this.itemSize);
    }
  }
};