Load Data on Demand

import { NgModule, Component, enableProdMode } from '@angular/core'; import { BrowserModule } from '@angular/platform-browser'; import { platformBrowserDynamic } from '@angular/platform-browser-dynamic'; import { HttpClient, HttpClientModule, HttpParams } from '@angular/common/http'; import { DxTreeListModule } from 'devextreme-angular'; if (!/localhost/.test(document.location.host)) { enableProdMode(); } @Component({ selector: 'demo-app', templateUrl: 'app/app.component.html', styleUrls: ['app/app.component.css'], }) export class AppComponent { dataSource: any; constructor(http: HttpClient) { this.dataSource = { load(loadOptions) { let params = new HttpParams(); if (loadOptions.parentIds) { loadOptions.parentIds.forEach((id) => { params = params.append('parentIds', id); }); } return http .get('https://js.devexpress.com/Demos/Mvc/api/treeListData', { params }) .toPromise(); }, }; } customizeSizeText(e) { if (e.value !== null) { return `${Math.ceil(e.value / 1024)} KB`; } } } @NgModule({ imports: [ BrowserModule, DxTreeListModule, HttpClientModule, ], declarations: [AppComponent], bootstrap: [AppComponent], }) export class AppModule { } platformBrowserDynamic().bootstrapModule(AppModule);

::ng-deep #treelist { max-height: 440px; }

// In real applications, you should not transpile code in the browser. // You can see how to create your own application with Angular and DevExtreme here: // https://js.devexpress.com/Documentation/Guide/Angular_Components/Getting_Started/Create_a_DevExtreme_Application/ window.config = { transpiler: 'ts', typescriptOptions: { module: 'system', emitDecoratorMetadata: true, experimentalDecorators: true, }, meta: { 'typescript': { 'exports': 'ts', }, 'devextreme/localization.js': { 'esModule': true, }, }, paths: { 'npm:': 'https://unpkg.com/', }, map: { 'ts': 'npm:plugin-typescript@8.0.0/lib/plugin.js', 'typescript': 'npm:typescript@3.5.3/lib/typescript.js', '@angular/core': 'npm:@angular/core@12.2.13', '@angular/platform-browser': 'npm:@angular/platform-browser@12.2.13', '@angular/platform-browser-dynamic': 'npm:@angular/platform-browser-dynamic@12.2.13', '@angular/forms': 'npm:@angular/forms@12.2.13', '@angular/common': 'npm:@angular/common@12.2.13', '@angular/compiler': 'npm:@angular/compiler@12.2.13', 'tslib': 'npm:tslib@2.3.1/tslib.js', 'rxjs': 'npm:rxjs@6.4.0', 'rrule': 'npm:rrule@2.6.6/dist/es5/rrule.js', 'luxon': 'npm:luxon@1.28.0/build/global/luxon.min.js', 'es6-object-assign': 'npm:es6-object-assign@1.1.0', 'devextreme': 'npm:devextreme@21.2.4/cjs', 'devextreme/bundles/dx.all': 'npm:devextreme@21.2.4/bundles/dx.all.js', 'jszip': 'npm:jszip@3.7.1/dist/jszip.min.js', 'devextreme-quill': 'npm:devextreme-quill@1.5.7/dist/dx-quill.min.js', 'devexpress-diagram': 'npm:devexpress-diagram@2.1.40', 'devexpress-gantt': 'npm:devexpress-gantt@4.0.0', 'devextreme-angular': 'npm:devextreme-angular@21.2.4', '@devextreme/runtime': 'npm:@devextreme/runtime@2.3.13', 'inferno': 'npm:inferno@7.4.11/dist/inferno.min.js', 'inferno-compat': 'npm:inferno-compat@7.4.11/dist/inferno-compat.min.js', 'inferno-create-element': 'npm:inferno-create-element@7.4.11/dist/inferno-create-element.min.js', 'inferno-dom': 'npm:inferno-dom/dist/inferno-dom.min.js', 'inferno-hydrate': 'npm:inferno-hydrate@7.4.11/dist/inferno-hydrate.min.js', 'inferno-clone-vnode': 'npm:inferno-clone-vnode@7.4.11/dist/inferno-clone-vnode.min.js', 'inferno-create-class': 'npm:inferno-create-class@7.4.11/dist/inferno-create-class.min.js', 'inferno-extras': 'npm:inferno-extras@7.4.11/dist/inferno-extras.min.js', }, packages: { 'app': { main: './app.component.ts', defaultExtension: 'ts', }, 'devextreme': { defaultExtension: 'js', }, 'devextreme/events/utils': { main: 'index', }, 'devextreme/events': { main: 'index', }, 'es6-object-assign': { main: './index.js', defaultExtension: 'js', }, }, packageConfigPaths: [ 'npm:@devextreme/*/package.json', 'npm:@devextreme/runtime@2.3.13/inferno/package.json', 'npm:@angular/*/package.json', 'npm:@angular/common@12.2.13/*/package.json', 'npm:rxjs@6.4.0/package.json', 'npm:rxjs@6.4.0/operators/package.json', 'npm:devextreme-angular@21.2.4/*/package.json', 'npm:devextreme-angular@21.2.4/ui/*/package.json', 'npm:devextreme-angular@21.2.4/package.json', 'npm:devexpress-diagram@2.1.40/package.json', 'npm:devexpress-gantt@4.0.0/package.json', ], }; System.config(window.config);

<!DOCTYPE html> <html xmlns="http://www.w3.org/1999/xhtml"> <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=1.0" /> <link rel="stylesheet" type="text/css" href="https://cdn3.devexpress.com/jslib/21.2.4/css/dx.common.css" /> <link rel="stylesheet" type="text/css" href="https://cdn3.devexpress.com/jslib/21.2.4/css/dx.light.css" /> <script src="https://unpkg.com/core-js@2.4.1/client/shim.min.js"></script> <script src="https://unpkg.com/zone.js@0.11.4/dist/zone.js"></script> <script src="https://unpkg.com/reflect-metadata@0.1.3/Reflect.js"></script> <script src="https://unpkg.com/systemjs@0.21.3/dist/system.js"></script> <script src="config.js"></script> <script> System.import("app").catch(console.error.bind(console)); </script> </head> <body class="dx-viewport"> <div class="demo-container"> <demo-app>Loading...</demo-app> </div> </body> </html>