解决ElementUI列表大数据操作卡顿问题

问题描述

前端UI框架使用的是ElementUI,项目要求数据不分页一个表格至少要1000条数据，这时点击其他DOM操作，会出现卡顿的现象。如点击复选框。

官网的示例也搞了，超过200行后操作就会卡很久，比如复选框

基于elementUI的table，在不修改源码的情况下支持大数据了渲染的场景

思路：
减少对DOM节点的渲染，通过滚动函数节流实现滚动后事件来动态渲染数据

解决方案：

Vue自定义指令 （通过自定义指令隐藏数据）

ele-table

<template>
  <div>
    <el-table border :data="filteredData" style="width: 100%" height="300" :data-size="tableData.length" v-loadmore="handelLoadmore">
      <el-table-column type="selection" width="55">
      </el-table-column>
      <el-table-column label="日期" width="180">
        <template slot-scope="scope">
          <div>
            <i class="el-icon-time"></i>
            <span style="margin-left: 10px">{{ scope.row.date }}</span>
          </div>
        </template>
      </el-table-column>
      <el-table-column label="日期" width="180">
        <template slot-scope="scope">
          <div>
            <i class="el-icon-time"></i>
            <span style="margin-left: 10px">{{ scope.row.date }}</span>
          </div>
        </template>
      </el-table-column>
      <el-table-column label="日期" width="180">
        <template slot-scope="scope">
          <div>
            <i class="el-icon-time"></i>
            <span style="margin-left: 10px">{{ scope.row.date }}</span>
          </div>
        </template>
      </el-table-column>
      <el-table-column label="日期" width="180">
        <template slot-scope="scope">
          <div>
            <i class="el-icon-time"></i>
            <span style="margin-left: 10px">{{ scope.row.date }}</span>
          </div>
        </template>
      </el-table-column>
      <el-table-column label="姓名" width="180">
        <template slot-scope="scope">
          <div>
            <el-popover trigger="hover" placement="top">
              <p>姓名: {{ scope.row.name }}</p>
              <p>住址: {{ scope.row.address }}</p>
              <div slot="reference" class="name-wrapper">
                <el-tag size="medium">{{ scope.row.name }}</el-tag>
              </div>
            </el-popover>
          </div>
        </template>
      </el-table-column>
      <el-table-column label="操作">
        <template slot-scope="scope">
          <div>
            <el-button size="mini"  @click="handleEdit(scope.$index, scope.row)">编辑</el-button>
            <el-button size="mini" type="danger"  @click="handleDelete(scope.$index, scope.row)">删除</el-button>
          </div>
        </template>
      </el-table-column>
    </el-table>
  </div>
</template>

<script>

export default {
  name: 'test',
  components: {},
  data () {
    return {
      tableData: [],
      currentStartIndex: 0,
      currentEndIndex: 20
    };
  },
  created () {
    this.getTableData();
  },
  computed: {
    filteredData () {
      return this.tableData.filter((item, index) => {
        if (index < this.currentStartIndex) {
          return false;
        } else if (index > this.currentEndIndex) {
          return false;
        } else {
          return true;
        }
      });
    }
  },
  methods: {
    handelLoadmore (currentStartIndex, currentEndIndex) {
      this.currentStartIndex = currentStartIndex;
      this.currentEndIndex = currentEndIndex;
    },
    getTableData () {
      let cont = 0;
      let tableData = [];
      while (cont < 30000) {
        cont = cont + 1;
        let object = {
          date: cont,
          name: '王小虎' + cont,
          address: '上海市普陀区金沙江路 cont 弄'
        }
        tableData.push(object);
      }
      setTimeout(() => {
        this.tableData = tableData;
      }, 2000);
    }
  },
  watch: {}
}
</script>

<style scoped>
.el-table__body-wrapper .el-table__row td {
  display: none;
}
.el-table__body-wrapper .el-table__row {
  height: 38px;
}
</style>

指令代码：

// 设置默认溢出显示数量
var spillDataNum = 20;

// 设置隐藏函数
var timeout = false;
let setRowDisableNone = function (topNum, showRowNum, binding) {
  if (timeout) {
    clearTimeout(timeout);
  }
  timeout = setTimeout(() => {
    binding.value.call(null, topNum, topNum + showRowNum + spillDataNum);
  });
};

export default {
  name: 'loadmore',
  componentUpdated: function (el, binding, vnode, oldVnode) {
    setTimeout(() => {
      const dataSize = vnode.data.attrs['data-size'];
      const oldDataSize = oldVnode.data.attrs['data-size'];
      if(dataSize === oldDataSize){
        return;
      }
      const selectWrap = el.querySelector('.el-table__body-wrapper');
      const selectTbody = selectWrap.querySelector('table tbody');
      const selectRow = selectWrap.querySelector('table tr');
      if (!selectRow) {
        return;
      }
      const rowHeight = selectRow.clientHeight;
      let showRowNum = Math.round(selectWrap.clientHeight / rowHeight);

      const createElementTR = document.createElement('tr');
      let createElementTRHeight = (dataSize - showRowNum - spillDataNum) * rowHeight;
      createElementTR.setAttribute('style', `height: ${createElementTRHeight}px;`);
      selectTbody.append(createElementTR);

      // 监听滚动后事件
      selectWrap.addEventListener('scroll', function () {
        let topPx = this.scrollTop - spillDataNum * rowHeight;
        let topNum = Math.round(topPx / rowHeight);
        let minTopNum = dataSize - spillDataNum - showRowNum;
        if (topNum > minTopNum) {
          topNum = minTopNum;
        }
        if (topNum < 0) {
          topNum = 0;
          topPx = 0;
        }
        selectTbody.setAttribute('style', `transform: translateY(${topPx}px)`);
        createElementTR.setAttribute('style', `height: ${createElementTRHeight-topPx > 0 ? createElementTRHeight-topPx : 0}px;`);
        setRowDisableNone(topNum, showRowNum, binding);
      })
    });
  }
};

全局main.js引用

import loadmore from '@/js/loadmore'
Vue.directive(loadmore.name,loadmore.componentUpdated);