Virtualization (Angular)

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 Angular.

import 'bootstrap.css'; import '@mescius/wijmo.styles/wijmo.css'; import './styles.css'; // import '@angular/compiler'; import { Component, enableProdMode, Inject, ɵresolveComponentResources } from '@angular/core'; import { BrowserModule, bootstrapApplication } from '@angular/platform-browser'; import * as wjcGrid from '@mescius/wijmo.grid'; import { WjGridModule } from '@mescius/wijmo.angular2.grid'; import { WjInputModule } from '@mescius/wijmo.angular2.input'; import { DataService } from './app.data'; // @Component({ standalone: true, providers: [DataService], imports: [WjGridModule, WjInputModule, BrowserModule], selector: 'app-component', templateUrl: 'src/app.component.html' }) export class AppComponent { data: any[]; dataSvc: DataService; rowCount: number; cellCount: number; constructor(@Inject(DataService) dataSvc: DataService) { this.data = dataSvc.getData(100); this.dataSvc = dataSvc; } initializeGrid(flex: wjcGrid.FlexGrid) { this.rowCount = flex.rows.length; this.cellCount = flex.hostElement.querySelectorAll('.wj-cell').length; flex.updatedView.addHandler((s: wjcGrid.FlexGrid) => { this.rowCount = s.rows.length; this.cellCount = s.hostElement.querySelectorAll('.wj-cell').length; }); flex.scrollPositionChanged.addHandler((s: wjcGrid.FlexGrid) => { // 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 this._addData(this.data, 20); view.refresh(); view.currentPosition = index; } }); } // add random data to an array private _addData(data: any[], cnt: number) { let more = this.dataSvc.getData(cnt, data.length); for (let i = 0; i < more.length; i++) { data.push(more[i]) } } } // enableProdMode(); // Resolve resources (templateUrl, styleUrls etc), After resolution all URLs have been converted into `template` strings. ɵresolveComponentResources(fetch).then(() => { // Bootstrap application bootstrapApplication(AppComponent).catch(err => console.error(err)); });
<!DOCTYPE html> <html lang="en"> <head> <meta charset="utf-8"> <meta http-equiv="X-UA-Compatible" content="IE=edge"> <title>MESCIUS Wijmo FlexGrid Scroll Virtualization</title> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <!-- Polyfills --> <script src="node_modules/core-js/client/shim.min.js"></script> <script src="node_modules/zone.js/fesm2015/zone.min.js"></script> <!-- SystemJS --> <script src="https://cdnjs.cloudflare.com/ajax/libs/systemjs/0.21.5/system.src.js" integrity="sha512-skZbMyvYdNoZfLmiGn5ii6KmklM82rYX2uWctBhzaXPxJgiv4XBwJnFGr5k8s+6tE1pcR1nuTKghozJHyzMcoA==" crossorigin="anonymous"></script> <script src="systemjs.config.js"></script> <script> // workaround to load 'rxjs/operators' from the rxjs bundle System.import('rxjs').then(function (m) { System.set(SystemJS.resolveSync('rxjs/operators'), System.newModule(m.operators)); System.import('./src/app.component'); }); </script> </head> <body> <app-component></app-component> </body> </html>
<div class="container-fluid"> <wj-flex-grid #flex (initialized)="initializeGrid(flex)" [(itemsSource)]="data"> </wj-flex-grid> <p> The grid now has <span id='rowCount'>{{rowCount}}</span> rows and <span id='cellCount'>{{cellCount}}</span> cell elements.</p> </div>
import { Injectable } from '@angular/core'; @Injectable() export class DataService { // get an array with random data getData(cnt: number, start?: number): any[] { 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; } }
.wj-flexgrid { height: 250px; } #rowCount, #cellCount { font-weight: bold; } body { margin-bottom: 24pt; }
(function (global) { SystemJS.config({ transpiler: './plugin-typescript.js', typescriptOptions: { "target": "ES2022", "module": "system", "emitDecoratorMetadata": true, "experimentalDecorators": true, }, baseURL: 'node_modules/', meta: { 'typescript': { "exports": "ts" }, '*.css': { loader: 'systemjs-plugin-css' } }, paths: { // paths serve as alias 'npm:': '' }, packageConfigPaths: [ '/node_modules/*/package.json', "/node_modules/@angular/*/package.json", "/node_modules/@mescius/*/package.json" ], map: { 'core-js': 'https://cdn.jsdelivr.net/npm/core-js@2.6.12/client/shim.min.js', 'typescript': 'https://cdnjs.cloudflare.com/ajax/libs/typescript/5.2.2/typescript.min.js', "rxjs": "https://cdnjs.cloudflare.com/ajax/libs/rxjs/7.8.1/rxjs.umd.min.js", 'systemjs-plugin-css': 'https://cdn.jsdelivr.net/npm/systemjs-plugin-css@0.1.37/css.js', '@mescius/wijmo': 'npm:@mescius/wijmo/index.js', '@mescius/wijmo.input': 'npm:@mescius/wijmo.input/index.js', '@mescius/wijmo.styles': 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packages: { "./src": { defaultExtension: 'ts' }, "node_modules": { defaultExtension: 'js' }, wijmo: { defaultExtension: 'js', } } }); })(this);