Angular Charts - Load Data On Demand

import { bootstrapApplication } from '@angular/platform-browser'; import { Component, ViewChild, enableProdMode, provideZoneChangeDetection } from '@angular/core'; import { HttpClient, provideHttpClient, withFetch } from '@angular/common/http'; import { lastValueFrom } from 'rxjs'; import { DxChartComponent, DxChartModule } from 'devextreme-angular'; import { VisualRange } from 'devextreme-angular/common/charts'; import { DataSource } from 'devextreme-angular/common/data'; if (!/localhost/.test(document.location.host)) { enableProdMode(); } @Component({ selector: 'demo-app', templateUrl: './app.component.html', styleUrls: ['./app.component.css'], imports: [ DxChartModule, ], }) export class AppComponent { @ViewChild(DxChartComponent, { static: false }) component: DxChartComponent; private _visualRange: VisualRange = { startValue: new Date(2025, 3, 1), length: { weeks: 2, }, }; HALFDAY = 43200000; packetsLock = 0; chartDataSource = new DataSource({ store: [], sort: 'date', paginate: false, }); bounds = { startValue: new Date(2025, 0, 1), endValue: new Date(2025, 11, 31), }; constructor(private httpClient: HttpClient) {} get currentVisualRange(): VisualRange { return this._visualRange; } set currentVisualRange(range: VisualRange) { this._visualRange.startValue = range.startValue; this._visualRange.endValue = range.endValue; this.onVisualRangeChanged(); } onVisualRangeChanged() { const items = this.component.instance.getDataSource().items(); const itemsFirstDate = items?.[0]?.date as number; const itemsLastDate = items?.[items.length - 1]?.date as number; const startDate = this._visualRange.startValue as number; const endDate = this._visualRange.endValue as number; if (!items.length || itemsFirstDate - startDate >= this.HALFDAY || endDate - itemsLastDate >= this.HALFDAY) { this.uploadDataByVisualRange(); } } uploadDataByVisualRange() { const dataSource = this.component.instance.getDataSource(); const ajaxArgs = { startVisible: this.getDateString(this._visualRange.startValue as Date), endVisible: this.getDateString(this._visualRange.endValue as Date), }; if (!this.packetsLock) { this.packetsLock += 1; this.component.instance.showLoadingIndicator(); this.getDataFrame(ajaxArgs) .then((dataFrame: Record<string, number | Date>[]) => { this.packetsLock -= 1; const componentStorage = dataSource.store(); dataFrame .map((i) => ({ date: new Date(i.Date), minTemp: i.MinTemp, maxTemp: i.MaxTemp, })) .forEach((item) => componentStorage.insert(item)); dataSource.reload(); this.onVisualRangeChanged(); }) .catch(() => { this.packetsLock -= 1; dataSource.reload(); }); } } getDataFrame(args: Record<string, string>) { const params = `startVisible=${args.startVisible}` + `&endVisible=${args.endVisible}`; return lastValueFrom( this.httpClient.get(`https://js.devexpress.com/Demos/NetCore/api/TemperatureData?${params}`), ); } getDateString(dateTime: Date) { return dateTime ? dateTime.toLocaleDateString('en-US') : ''; } } bootstrapApplication(AppComponent, { providers: [ provideZoneChangeDetection({ eventCoalescing: true, runCoalescing: true }), provideHttpClient(withFetch()), ], });

::ng-deep #chart { height: 440px; }

<!DOCTYPE html> <html lang="en"> <head> <title>DevExtreme Demo</title> <meta http-equiv="X-UA-Compatible" content="IE=edge" /> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=5.0" /> <link rel="stylesheet" type="text/css" href="https://cdn3.devexpress.com/jslib/26.1.5/css/dx.light.css" /> </head> <body class="dx-viewport"> <div class="demo-container"> <demo-app>Loading...</demo-app> </div> <script src="https://cdn.jsdelivr.net/npm/zone.js@0.16.2/bundles/zone.umd.js"></script> <script src="./bundle.js" type="module"></script> </body> </html>