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Load Data On Demand

In this demo, the range area Chart loads data as you pan it. Once the component loads a data block, this data stays in memory to reduce requests to the server.

www.kaggle.com
Backend API
import React, { useState } from 'react'; import DataSource from 'devextreme/data/data_source'; import { Chart, ChartTypes, ZoomAndPan, ScrollBar, ArgumentAxis, ValueAxis, Title, Label, Font, Legend, Series, Animation, LoadingIndicator, } from 'devextreme-react/chart'; const HALFDAY = 43200000; let packetsLock = 0; const chartDataSource = new DataSource({ store: [], sort: 'date', paginate: false, }); const wholeRange = { startValue: new Date(2017, 0, 1), endValue: new Date(2017, 11, 31), }; function App() { const [visualRange, setVisualRange] = useState({ startValue: new Date(2017, 3, 1), endValue: new Date(2017, 3, 15), }); const handleChange = (e: ChartTypes.OptionChangedEvent) => { if (e.fullName === 'argumentAxis.visualRange') { const stateStart = visualRange.startValue; const currentStart = e.value.startValue; if (stateStart.valueOf() !== currentStart.valueOf()) { setVisualRange(e.value); } onVisualRangeChanged(e.value, e.component); } }; return ( <Chart id="chart" title="Temperature in Toronto (2017)" dataSource={chartDataSource} onOptionChanged={handleChange} > <ZoomAndPan argumentAxis="pan" /> <ScrollBar visible={true} /> <ArgumentAxis argumentType="datetime" visualRangeUpdateMode="keep" visualRange={visualRange} wholeRange={wholeRange} /> <ValueAxis name="temperature" allowDecimals={false}> <Title text='Temperature, &deg;C'> <Font color="#ff950c" /> </Title> <Label> <Font color="#ff950c" /> </Label> </ValueAxis> <Series color="#ff950c" type="rangearea" argumentField="date" rangeValue1Field="minTemp" rangeValue2Field="maxTemp" name="Temperature range" /> <Animation enabled={false} /> <LoadingIndicator backgroundColor="none"> <Font size={14} /> </LoadingIndicator> <Legend visible={false} /> </Chart> ); } const uploadDataByVisualRange = (visualRange, component) => { const dataSource = component.getDataSource(); const storage = dataSource.items(); const ajaxArgs = { startVisible: getDateString(visualRange.startValue), endVisible: getDateString(visualRange.endValue), startBound: getDateString(storage.length ? storage[0].date : null), endBound: getDateString( storage.length ? storage[storage.length - 1].date : null, ), }; if ( ajaxArgs.startVisible !== ajaxArgs.startBound && ajaxArgs.endVisible !== ajaxArgs.endBound && !packetsLock ) { packetsLock += 1; component.showLoadingIndicator(); getDataFrame(ajaxArgs) .then((dataFrame) => { 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(); onVisualRangeChanged(visualRange, component); }) .catch(() => { packetsLock -= 1; dataSource.reload(); }); } }; const onVisualRangeChanged = (visualRange, component) => { const items = component.getDataSource().items(); if ( !items.length || items[0].date - visualRange.startValue.getTime() >= HALFDAY || visualRange.endValue.getTime() - items[items.length - 1].date >= HALFDAY ) { uploadDataByVisualRange(visualRange, component); } }; function getDataFrame(args) { let params = '?'; params += `startVisible=${args.startVisible} &endVisible=${args.endVisible} &startBound=${args.startBound} &endBound=${args.endBound}`; return fetch( `https://js.devexpress.com/Demos/WidgetsGallery/data/temperatureData${params}`, ).then((response) => response.json()); } function getDateString(dateTime) { return dateTime ? dateTime.toLocaleDateString('en-US') : ''; } export default App;
import React, { useState } from 'react'; import DataSource from 'devextreme/data/data_source'; import { Chart, ZoomAndPan, ScrollBar, ArgumentAxis, ValueAxis, Title, Label, Font, Legend, Series, Animation, LoadingIndicator, } from 'devextreme-react/chart'; const HALFDAY = 43200000; let packetsLock = 0; const chartDataSource = new DataSource({ store: [], sort: 'date', paginate: false, }); const wholeRange = { startValue: new Date(2017, 0, 1), endValue: new Date(2017, 11, 31), }; function App() { const [visualRange, setVisualRange] = useState({ startValue: new Date(2017, 3, 1), endValue: new Date(2017, 3, 15), }); const handleChange = (e) => { if (e.fullName === 'argumentAxis.visualRange') { const stateStart = visualRange.startValue; const currentStart = e.value.startValue; if (stateStart.valueOf() !== currentStart.valueOf()) { setVisualRange(e.value); } onVisualRangeChanged(e.value, e.component); } }; return ( <Chart id="chart" title="Temperature in Toronto (2017)" dataSource={chartDataSource} onOptionChanged={handleChange} > <ZoomAndPan argumentAxis="pan" /> <ScrollBar visible={true} /> <ArgumentAxis argumentType="datetime" visualRangeUpdateMode="keep" visualRange={visualRange} wholeRange={wholeRange} /> <ValueAxis name="temperature" allowDecimals={false} > <Title text="Temperature, &deg;C"> <Font color="#ff950c" /> </Title> <Label> <Font color="#ff950c" /> </Label> </ValueAxis> <Series color="#ff950c" type="rangearea" argumentField="date" rangeValue1Field="minTemp" rangeValue2Field="maxTemp" name="Temperature range" /> <Animation enabled={false} /> <LoadingIndicator backgroundColor="none"> <Font size={14} /> </LoadingIndicator> <Legend visible={false} /> </Chart> ); } const uploadDataByVisualRange = (visualRange, component) => { const dataSource = component.getDataSource(); const storage = dataSource.items(); const ajaxArgs = { startVisible: getDateString(visualRange.startValue), endVisible: getDateString(visualRange.endValue), startBound: getDateString(storage.length ? storage[0].date : null), endBound: getDateString(storage.length ? storage[storage.length - 1].date : null), }; if ( ajaxArgs.startVisible !== ajaxArgs.startBound && ajaxArgs.endVisible !== ajaxArgs.endBound && !packetsLock ) { packetsLock += 1; component.showLoadingIndicator(); getDataFrame(ajaxArgs) .then((dataFrame) => { 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(); onVisualRangeChanged(visualRange, component); }) .catch(() => { packetsLock -= 1; dataSource.reload(); }); } }; const onVisualRangeChanged = (visualRange, component) => { const items = component.getDataSource().items(); if ( !items.length || items[0].date - visualRange.startValue.getTime() >= HALFDAY || visualRange.endValue.getTime() - items[items.length - 1].date >= HALFDAY ) { uploadDataByVisualRange(visualRange, component); } }; function getDataFrame(args) { let params = '?'; params += `startVisible=${args.startVisible} &endVisible=${args.endVisible} &startBound=${args.startBound} &endBound=${args.endBound}`; return fetch(`https://js.devexpress.com/Demos/WidgetsGallery/data/temperatureData${params}`).then( (response) => response.json(), ); } function getDateString(dateTime) { return dateTime ? dateTime.toLocaleDateString('en-US') : ''; } 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, }, }, paths: { 'npm:': 'https://unpkg.com/', }, defaultExtension: 'js', map: { 'ts': 'npm:plugin-typescript@4.2.4/lib/plugin.js', 'typescript': 'npm:typescript@4.2.4/lib/typescript.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@15.8.1/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@1.28.1/build/global/luxon.min.js', 'es6-object-assign': 'npm:es6-object-assign@1.1.0', 'devextreme': 'npm:devextreme@24.1.3/cjs', 'devextreme-react': 'npm:devextreme-react@24.1.3/cjs', 'jszip': 'npm:jszip@3.10.1/dist/jszip.min.js', 'devextreme-quill': 'npm:devextreme-quill@1.7.1/dist/dx-quill.min.js', 'devexpress-diagram': 'npm:devexpress-diagram@2.2.8/dist/dx-diagram.js', 'devexpress-gantt': 'npm:devexpress-gantt@4.1.56/dist/dx-gantt.js', '@devextreme/runtime': 'npm:@devextreme/runtime@3.0.13', '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@7.4.11/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/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@3.0.13/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> <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/24.1.3/css/dx.light.css" /> <link rel="stylesheet" type="text/css" href="styles.css" /> <script src="https://unpkg.com/core-js@2.6.12/client/shim.min.js"></script> <script src="https://unpkg.com/systemjs@0.21.3/dist/system.js"></script> <script type="text/javascript" src="config.js"></script> <script type="text/javascript"> System.import("./index.tsx"); </script> </head> <body class="dx-viewport"> <div class="demo-container"> <div id="app"></div> </div> </body> </html>
#chart { height: 440px; }

To implement this functionality, do the following:

  1. Configure a data source.

  2. Configure the Chart to support on-demand data loading.

  3. Implement functions that load the data.

    • In this demo, Chart displays daily information. If a user pan the Chart left or right more than half a day, additional data starts to load. The onVisualRangeChanged initiates this procedure.

    • The uploadDataByVisualRange function analyzes the starting and ending points of the visual range and the bounds of already loaded data. If necessary, it calls the getDataFrame function to obtain new data points. Finally, it reloads the DataSource and saves the current visual range.

    • The getDataFrame Ajax request gets the new data frame from the server.