React Tree List - Load Data on Demand

import React from 'react';

import { TreeList, RemoteOperations, Column } from 'devextreme-react/tree-list';

import 'whatwg-fetch';

​

const dataSource = {

  async load(loadOptions) {

    const parentIdsParam = loadOptions.parentIds;

    const url = new URL('https://js.devexpress.com/Demos/NetCore/api/treeListData');

    if (parentIdsParam) {

      parentIdsParam.forEach((id) => {

        url.searchParams.append('parentIds', id);

      });

    }

    const result = await fetch(url.toString());

    if (result.status === 200) {

      return result.json();

    }

    throw new Error('Data Loading Error');

  },

};

const customizeText = (e) => {

  if (e.value !== null) {

    return `${Math.ceil(e.value / 1024)} KB`;

  }

  return null;

};

const App = () => (

  <TreeList

    id="treelist"

    dataSource={dataSource}

    showBorders={true}

    keyExpr="id"

    parentIdExpr="parentId"

    hasItemsExpr="hasItems"

    rootValue=""

  >

    <RemoteOperations filtering={true} />

    <Column dataField="name" />

    <Column

      width={100}

      customizeText={customizeText}

      dataField="size"

    />

    <Column

      width={150}

      dataField="createdDate"

      dataType="date"

    />

    <Column

      width={150}

      dataField="modifiedDate"

      dataType="date"

    />

  </TreeList>

);

export default App;

​

import React from 'react';

import ReactDOM from 'react-dom';

​

import App from './App.tsx';

​

ReactDOM.render(

  <App />,

  document.getElementById('app'),

);

​

window.exports = window.exports || {};

window.config = {

  transpiler: 'ts',

  typescriptOptions: {

    module: 'system',

    emitDecoratorMetadata: true,

    experimentalDecorators: true,

    jsx: 'react',

  },

  meta: {

    'react': {

      'esModule': true,

    },

    'typescript': {

      'exports': 'ts',

    },

    'devextreme/time_zone_utils.js': {

      'esModule': true,

    },

    'devextreme/localization.js': {

      'esModule': true,

    },

    'devextreme/viz/palette.js': {

      'esModule': true,

    },

    'openai': {

      'esModule': true,

    },

  },

  paths: {

    'npm:': 'https://unpkg.com/',

    'bundles:': 'bundles/',

    'externals:': 'bundles/externals/',

  },

  defaultExtension: 'js',

  map: {

    'ts': 'npm:plugin-typescript@8.0.0/lib/plugin.js',

    'typescript': 'npm:typescript@4.2.4/lib/typescript.js',

    'jszip': 'npm:jszip@3.10.1/dist/jszip.min.js',

    'react': 'npm:react@17.0.2/umd/react.development.js',

    'react-dom': 'npm:react-dom@17.0.2/umd/react-dom.development.js',

    'prop-types': 'npm:prop-types/prop-types.js',

    'whatwg-fetch': 'npm:whatwg-fetch@2.0.4/fetch.js',

    'rrule': 'npm:rrule@2.6.4/dist/es5/rrule.js',

    'luxon': 'npm:luxon@3.4.4/build/global/luxon.min.js',

    'es6-object-assign': 'npm:es6-object-assign',

    'devextreme': 'npm:devextreme@24.2.6/cjs',

    'devextreme-react': 'npm:devextreme-react@24.2.6/cjs',

    'devextreme-quill': 'npm:devextreme-quill@1.7.1/dist/dx-quill.min.js',

    'devexpress-diagram': 'npm:devexpress-diagram@2.2.15/dist/dx-diagram.js',

    'devexpress-gantt': 'npm:devexpress-gantt@4.1.60/dist/dx-gantt.js',

    '@devextreme/runtime': 'npm:@devextreme/runtime@3.0.12',

    'inferno': 'npm:inferno@7.4.11/dist/inferno.min.js',

    'inferno-compat': 'npm:inferno-compat/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/dist/inferno-hydrate.min.js',

    'inferno-clone-vnode': 'npm:inferno-clone-vnode/dist/inferno-clone-vnode.min.js',

    'inferno-create-class': 'npm:inferno-create-class/dist/inferno-create-class.min.js',

    'inferno-extras': 'npm:inferno-extras/dist/inferno-extras.min.js',

    'devextreme-cldr-data': 'npm:devextreme-cldr-data@1.0.3',

    // SystemJS plugins

    'plugin-babel': 'npm:systemjs-plugin-babel@0.0.25/plugin-babel.js',

    'systemjs-babel-build': 'npm:systemjs-plugin-babel@0.0.25/systemjs-babel-browser.js',

    // Prettier

    'prettier/standalone': 'npm:prettier@2.8.8/standalone.js',

    'prettier/parser-html': 'npm:prettier@2.8.8/parser-html.js',

  },

  packages: {

    'devextreme': {

      defaultExtension: 'js',

    },

    'devextreme-react': {

      main: 'index.js',

    },

    'devextreme/events/utils': {

      main: 'index',

    },

    'devextreme/common/core/events/utils': {

      main: 'index',

    },

    'devextreme/localization/messages': {

      format: 'json',

      defaultExtension: 'json',

    },

    'devextreme/events': {

      main: 'index',

    },

    'es6-object-assign': {

      main: './index.js',

      defaultExtension: 'js',

    },

  },

  packageConfigPaths: [

    'npm:@devextreme/*/package.json',

    'npm:@devextreme/runtime@3.0.12/inferno/package.json',

  ],

  babelOptions: {

    sourceMaps: false,

    stage0: true,

    react: true,

  },

};

System.config(window.config);

​

import React from 'react';

import ReactDOM from 'react-dom';

import App from './App.js';

​

ReactDOM.render(<App />, document.getElementById('app'));

​

<!DOCTYPE html>

<html lang="en">

  <head>↔</head>

​

  <body class="dx-viewport">

    <div class="demo-container">

      <div id="app"></div>

    </div>

  </body>

</html>

​

#treelist {

  max-height: 440px;

}

​