React虚拟渲染实现50个或者一百个图表渲染

import React, { useRef, useState, useEffect } from 'react';
import { requestTimeout, cancelTimeout } from '../../utils/timer';
import styles from './index.less';
const VirtualScroll = ({ data, itemHeight, preload = 1, renderItem }) => {
  const [v, setUpdateValue] = useState(0); // 用来更新组件
  const containerRef = useRef(null);
  const resetIsScrollingTimeoutId = useRef(null);
  /**
  * 可视区域滚动事件
  * 防抖处理
  */
  const onScroll = (e) => {
    if (resetIsScrollingTimeoutId.current !== null) {
      cancelTimeout(resetIsScrollingTimeoutId.current);
    }
    resetIsScrollingTimeoutId.current = requestTimeout(
      () => { setUpdateValue(val => (val + 1)); },
      150
    );
  }
  useEffect(() => {
    if (containerRef.current) {
      setUpdateValue(val => (val + 1));
    }
  }, [containerRef.current])
  if (!containerRef.current) {
    return <div className={styles.container} ref={containerRef}></div>;
  }
  let start = 0; // 开始的索引
  let end = 0; // 结束索引
  // const screenHeight = 300;
  const { scrollTop, offsetHeight: screenHeight } = containerRef.current;
  const visibleCount = Math.ceil((screenHeight / itemHeight)); // 显示的数量
  start = Math.floor(((scrollTop + screenHeight) / itemHeight)) - preload; // 开始的索引
  start = start < 0 ? 0 : start; // 判断边界
  end = start + visibleCount + preload; //
  end = end > data.length ? data.length : end; // 判断结束边界
  const visibleData = data.map((item, index) => {
    item.index = index;
    return item;
  }).slice(start, end);
  /**
  * ${data.length * itemHeight}px 容器的总高度
  * ${ item.index * itemHeight}px 没个元素的高度
  */
  return (
    <div className={styles.container} ref={containerRef} onScroll={onScroll}>
      <div style={{ width: '100%', height: `${data.length * itemHeight}px`, }}>
        {
          visibleData?.map((item, index) => {
            return <div key={item.index} style={{ position: 'absolute', width: '100%', height: `${itemHeight}px`, top: `${ item.index * itemHeight}px`}}>
              {renderItem(item)}
            </div>
          })
        }
      </div>
    </div>
  );
}
export default VirtualScroll;

const now = () => Date.now();
export function cancelTimeout(timeoutID) {
  cancelAnimationFrame(timeoutID.id);
}
export function requestTimeout(callback, delay) {
  const start = now();
  function tick() {
    if (now() - start >= delay) {
      callback.call(null);
    } else {
      timeoutID.id = requestAnimationFrame(tick);
    }
  }
  const timeoutID = {
    id: requestAnimationFrame(tick),
  };
  return timeoutID;
}

import React from 'react';
import { FullScreenBox, VirtualScroll } from '../../../components';
import { BarChart } from 'charts';
import { Row, Col, Select } from 'antd';
//造数据
let eventRateData = [];
for (let index = 0; index < 60; index++) {
  const d = [
    { x: 'text', y: 3.0, itemType: null, count: 0 },
    { x: 'asdasdzzzcv', y: 1.0, itemType: null, count: 0 },
  ];
  d.cacheIndex = index + 1;
  eventRateData.push(d)
}
// 对数据进行分组，每组有3条chart数据
function arrayGroup(arr, count = 3) {
  const arrResult = [];
  let begin = 0;
  let end = count;
  for (let i = 0; i < Math.ceil(arr.length / count); i++) {
    const splitArr = arr.slice(begin, end);
    arrResult.push(splitArr);
    begin = end;
    end = end + count;
  }
  return arrResult;
}
function Chart({ data }) {
  return <BarChart data={data} height={200} title alias={['数据集名称', '引用次数']} />
}
const EventView = props => {
  const [state, setState] = useImmer({
    count: 20
  })
  let data = eventRateData.slice(0, state.count);
  data = arrayGroup(data, 3);
  const renderItem = (item) => {
    return <Row>
      {
        item.map(child => {
          return <Col span={8} style={{ height: '200px' }}>
            <Chart data={child} title alias={['数据集名称', '引用次数']} />
          </Col>
        })
      }
    </Row>
  }
  return (
      <VirtualScroll
        renderItem={renderItem}
        data={data}
        itemHeight={200}
        preload={3}
      >
      </VirtualScroll>
  );
}
export default EventView;