Virtualization (React)

The FlexGrid control allows you to implement a simple type of 'infinite scrolling' through the use of the viewRange property. When the user scrolls to the bottom of the grid, the code adds items to the grid's itemsSource. If you inspect the DOM, you will notice that no matter how large the itemsSource gets, the number of DOM elements remains constant. The data is 'virtualized'.

Learn about FlexGrid | FlexGrid API Reference

This example uses React.

import 'bootstrap.css'; import '@mescius/wijmo.styles/wijmo.css'; import ReactDOM from 'react-dom/client'; import React, { useState } from 'react'; import useEvent from 'react-use-event-hook'; import * as wjcGrid from '@mescius/wijmo.react.grid'; import './app.css'; import { data, getData } from './data'; function App() { const [rowCount, setRowCount] = useState(0); const [cellCount, setCellCount] = useState(0); const initializeGrid = useEvent((flex) => { setRowCount(flex.rows.length); setCellCount(flex.hostElement.querySelectorAll('.wj-cell').length); flex.updatedView.addHandler((s) => { setRowCount(flex.rows.length); setCellCount(flex.hostElement.querySelectorAll('.wj-cell').length); }); flex.scrollPositionChanged.addHandler((s) => { // if we're close to the bottom, add 20 items if (s.viewRange.bottomRow >= s.rows.length - 1) { let view = s.collectionView; let index = view.currentPosition; // keep position in case the view is sorted addData(data, 20); view.refresh(); view.currentPosition = index; } }); }); const addData = (data, cnt) => { let more = getData(cnt, data.length); for (let i = 0; i < more.length; i++) { data.push(more[i]); } }; return (<div className="container-fluid"> <wjcGrid.FlexGrid initialized={initializeGrid} itemsSource={data}/> <p> The grid now has <span id='rowCount'>{rowCount}</span> rows and {' '}<span id='cellCount'>{cellCount}</span> cell elements. </p> </div>); } const container = document.getElementById('app'); if (container) { const root = ReactDOM.createRoot(container); root.render(<App />); }
<!DOCTYPE html> <html lang="en"> <head> <meta charset="utf-8"> <meta http-equiv="X-UA-Compatible" content="IE=edge"> <title>MESCIUS Wijmo Wijmo FlexGrid Scroll Virtualization</title> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <!-- SystemJS --> <script src="https://cdnjs.cloudflare.com/ajax/libs/systemjs/0.19.40/system.src.js" integrity="sha512-G6mEj6h18+m3MvzdviSDfPle/TfH0//cXcB33AKlNR/Rha0yQsKefDZKRTkIZos97HEGq2JMV1RT5ybMoQ3WsQ==" crossorigin="anonymous"></script> <script src="systemjs.config.js"></script> <script> System.import('./src/app'); </script> </head> <body> <div id="app"></div> </body> </html>
.wj-flexgrid { height: 250px; } #rowCount, #cellCount { font-weight: bold; }
export function getData(cnt, start) { let data = []; let countries = 'USA,Germany,UK,Japan,Italy,Greece'.split(','); if (!start) start = 0; for (let i = 0; i < cnt; i++) { data.push({ id: i + start, country: countries[i % countries.length], date: new Date(2014, i % 12, i % 28), amount: Math.random() * 10000, active: i % 4 === 0 }); } return data; } export const data = getData(100);
(function (global) { System.config({ transpiler: 'plugin-babel', babelOptions: { es2015: true, react: true }, meta: { '*.css': { loader: 'css' } }, paths: { // paths serve as alias 'npm:': 'node_modules/' }, // map tells the System loader where to look for things map: { 'jszip': 'npm:jszip/dist/jszip.js', '@mescius/wijmo': 'npm:@mescius/wijmo/index.js', '@mescius/wijmo.input': 'npm:@mescius/wijmo.input/index.js', '@mescius/wijmo.styles': 'npm:@mescius/wijmo.styles', '@mescius/wijmo.cultures': 'npm:@mescius/wijmo.cultures', '@mescius/wijmo.chart': 'npm:@mescius/wijmo.chart/index.js', '@mescius/wijmo.chart.analytics': 'npm:@mescius/wijmo.chart.analytics/index.js', '@mescius/wijmo.chart.animation': 'npm:@mescius/wijmo.chart.animation/index.js', '@mescius/wijmo.chart.annotation': 'npm:@mescius/wijmo.chart.annotation/index.js', '@mescius/wijmo.chart.finance': 'npm:@mescius/wijmo.chart.finance/index.js', '@mescius/wijmo.chart.finance.analytics': 'npm:@mescius/wijmo.chart.finance.analytics/index.js', '@mescius/wijmo.chart.hierarchical': 'npm:@mescius/wijmo.chart.hierarchical/index.js', '@mescius/wijmo.chart.interaction': 'npm:@mescius/wijmo.chart.interaction/index.js', '@mescius/wijmo.chart.radar': 'npm:@mescius/wijmo.chart.radar/index.js', '@mescius/wijmo.chart.render': 'npm:@mescius/wijmo.chart.render/index.js', '@mescius/wijmo.chart.webgl': 'npm:@mescius/wijmo.chart.webgl/index.js', '@mescius/wijmo.chart.map': 'npm:@mescius/wijmo.chart.map/index.js', '@mescius/wijmo.gauge': 'npm:@mescius/wijmo.gauge/index.js', '@mescius/wijmo.grid': 'npm:@mescius/wijmo.grid/index.js', '@mescius/wijmo.grid.detail': 'npm:@mescius/wijmo.grid.detail/index.js', '@mescius/wijmo.grid.filter': 'npm:@mescius/wijmo.grid.filter/index.js', '@mescius/wijmo.grid.search': 'npm:@mescius/wijmo.grid.search/index.js', '@mescius/wijmo.grid.grouppanel': 'npm:@mescius/wijmo.grid.grouppanel/index.js', '@mescius/wijmo.grid.multirow': 'npm:@mescius/wijmo.grid.multirow/index.js', '@mescius/wijmo.grid.transposed': 'npm:@mescius/wijmo.grid.transposed/index.js', '@mescius/wijmo.grid.transposedmultirow': 'npm:@mescius/wijmo.grid.transposedmultirow/index.js', '@mescius/wijmo.grid.pdf': 'npm:@mescius/wijmo.grid.pdf/index.js', '@mescius/wijmo.grid.sheet': 'npm:@mescius/wijmo.grid.sheet/index.js', '@mescius/wijmo.grid.xlsx': 'npm:@mescius/wijmo.grid.xlsx/index.js', '@mescius/wijmo.grid.selector': 'npm:@mescius/wijmo.grid.selector/index.js', '@mescius/wijmo.grid.cellmaker': 'npm:@mescius/wijmo.grid.cellmaker/index.js', '@mescius/wijmo.grid.immutable': 'npm:@mescius/wijmo.grid.immutable/index.js', '@mescius/wijmo.touch': 'npm:@mescius/wijmo.touch/index.js', '@mescius/wijmo.cloud': 'npm:@mescius/wijmo.cloud/index.js', '@mescius/wijmo.nav': 'npm:@mescius/wijmo.nav/index.js', '@mescius/wijmo.odata': 'npm:@mescius/wijmo.odata/index.js', '@mescius/wijmo.olap': 'npm:@mescius/wijmo.olap/index.js', '@mescius/wijmo.rest': 'npm:@mescius/wijmo.rest/index.js', '@mescius/wijmo.pdf': 'npm:@mescius/wijmo.pdf/index.js', '@mescius/wijmo.pdf.security': 'npm:@mescius/wijmo.pdf.security/index.js', '@mescius/wijmo.viewer': 'npm:@mescius/wijmo.viewer/index.js', '@mescius/wijmo.xlsx': 'npm:@mescius/wijmo.xlsx/index.js', '@mescius/wijmo.undo': 'npm:@mescius/wijmo.undo/index.js', '@mescius/wijmo.interop.grid': 'npm:@mescius/wijmo.interop.grid/index.js', '@mescius/wijmo.barcode': 'npm:@mescius/wijmo.barcode/index.js', '@mescius/wijmo.barcode.common': 'npm:@mescius/wijmo.barcode.common/index.js', '@mescius/wijmo.barcode.composite': 'npm:@mescius/wijmo.barcode.composite/index.js', '@mescius/wijmo.barcode.specialized': 'npm:@mescius/wijmo.barcode.specialized/index.js', "@mescius/wijmo.react.chart.analytics": "npm:@mescius/wijmo.react.chart.analytics/index.js", "@mescius/wijmo.react.chart.animation": "npm:@mescius/wijmo.react.chart.animation/index.js", "@mescius/wijmo.react.chart.annotation": "npm:@mescius/wijmo.react.chart.annotation/index.js", "@mescius/wijmo.react.chart.finance.analytics": "npm:@mescius/wijmo.react.chart.finance.analytics/index.js", "@mescius/wijmo.react.chart.finance": "npm:@mescius/wijmo.react.chart.finance/index.js", "@mescius/wijmo.react.chart.hierarchical": "npm:@mescius/wijmo.react.chart.hierarchical/index.js", "@mescius/wijmo.react.chart.interaction": "npm:@mescius/wijmo.react.chart.interaction/index.js", "@mescius/wijmo.react.chart.radar": "npm:@mescius/wijmo.react.chart.radar/index.js", "@mescius/wijmo.react.chart": "npm:@mescius/wijmo.react.chart/index.js", "@mescius/wijmo.react.core": "npm:@mescius/wijmo.react.core/index.js", '@mescius/wijmo.react.chart.map': 'npm:@mescius/wijmo.react.chart.map/index.js', "@mescius/wijmo.react.gauge": "npm:@mescius/wijmo.react.gauge/index.js", "@mescius/wijmo.react.grid.detail": "npm:@mescius/wijmo.react.grid.detail/index.js", "@mescius/wijmo.react.grid.filter": "npm:@mescius/wijmo.react.grid.filter/index.js", "@mescius/wijmo.react.grid.grouppanel": "npm:@mescius/wijmo.react.grid.grouppanel/index.js", '@mescius/wijmo.react.grid.search': 'npm:@mescius/wijmo.react.grid.search/index.js', "@mescius/wijmo.react.grid.multirow": "npm:@mescius/wijmo.react.grid.multirow/index.js", "@mescius/wijmo.react.grid.sheet": "npm:@mescius/wijmo.react.grid.sheet/index.js", '@mescius/wijmo.react.grid.transposed': 'npm:@mescius/wijmo.react.grid.transposed/index.js', '@mescius/wijmo.react.grid.transposedmultirow': 'npm:@mescius/wijmo.react.grid.transposedmultirow/index.js', '@mescius/wijmo.react.grid.immutable': 'npm:@mescius/wijmo.react.grid.immutable/index.js', "@mescius/wijmo.react.grid": "npm:@mescius/wijmo.react.grid/index.js", "@mescius/wijmo.react.input": "npm:@mescius/wijmo.react.input/index.js", "@mescius/wijmo.react.olap": "npm:@mescius/wijmo.react.olap/index.js", "@mescius/wijmo.react.viewer": "npm:@mescius/wijmo.react.viewer/index.js", "@mescius/wijmo.react.nav": "npm:@mescius/wijmo.react.nav/index.js", "@mescius/wijmo.react.base": "npm:@mescius/wijmo.react.base/index.js", '@mescius/wijmo.react.barcode.common': 'npm:@mescius/wijmo.react.barcode.common/index.js', '@mescius/wijmo.react.barcode.composite': 'npm:@mescius/wijmo.react.barcode.composite/index.js', '@mescius/wijmo.react.barcode.specialized': 'npm:@mescius/wijmo.react.barcode.specialized/index.js', 'jszip': 'npm:jszip/dist/jszip.js', 'react': 'npm:react/umd/react.production.min.js', 'react-dom': 'npm:react-dom/umd/react-dom.production.min.js', 'react-dom/client': 'npm:react-dom/umd/react-dom.production.min.js', 'redux': 'npm:redux/dist/redux.min.js', 'react-redux': 'npm:react-redux/dist/react-redux.min.js', 'bootstrap.css': 'npm:bootstrap/dist/css/bootstrap.min.css', 'css': 'npm:systemjs-plugin-css/css.js', 'plugin-babel': 'npm:systemjs-plugin-babel/plugin-babel.js', 'systemjs-babel-build':'npm:systemjs-plugin-babel/systemjs-babel-browser.js', "react-use-event-hook": "npm:react-use-event-hook/dist/esm/useEvent.js", }, // packages tells the System loader how to load when no filename and/or no extension packages: { src: { defaultExtension: 'jsx' }, "node_modules": { defaultExtension: 'js' }, } }); })(this);