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Charts

Load Data On Demand

In this demo, the chart loads data as you pan it. Once a data block is loaded, it stays in memory to reduce requests to the server.

www.worldweatheronline.com
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import React 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'; class App extends React.Component { constructor(props) { super(props); this.packetsLock = 0; this.HALFDAY = 43200000; this.chartDataSource = new DataSource({ store: [], sort: 'date', paginate: false }); this.state = { visualRange: { startValue: new Date(2017, 3, 1), endValue: new Date(2017, 3, 15) } }; this.handleChange = this.handleChange.bind(this); } render() { return ( <Chart id={'chart'} title={'Temperature in Toronto (2017)'} dataSource={this.chartDataSource} onOptionChanged={this.handleChange} > <ZoomAndPan argumentAxis={'pan'} /> <ScrollBar visible={true} /> <ArgumentAxis argumentType={'datetime'} visualRangeUpdateMode={'keep'} visualRange={this.state.visualRange} wholeRange={{ startValue: new Date(2017, 0, 1), endValue: new Date(2017, 11, 31) }} /> <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> ); } handleChange(e) { if(e.fullName === 'argumentAxis.visualRange') { const stateStart = this.state.visualRange.startValue; const currentStart = e.value.startValue; if(stateStart.valueOf() !== currentStart.valueOf()) { this.setState({ visualRange: e.value }); } this.onVisualRangeChanged(e.component); } } onVisualRangeChanged(component) { const items = component.getDataSource().items(); const visualRange = this.state.visualRange; if(!items.length || items[0].date - visualRange.startValue >= this.HALFDAY || visualRange.endValue - items[items.length - 1].date >= this.HALFDAY) { this.uploadDataByVisualRange(visualRange, component); } } 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 && !this.packetsLock) { this.packetsLock++; component.showLoadingIndicator(); getDataFrame(ajaxArgs) .then(dataFrame => { this.packetsLock--; dataFrame = dataFrame.map(i => { return { date: new Date(i.Date), minTemp: i.MinTemp, maxTemp: i.MaxTemp }; }); const componentStorage = dataSource.store(); dataFrame.forEach(item => componentStorage.insert(item)); dataSource.reload(); this.onVisualRangeChanged(component); }) .catch(() => { this.packetsLock--; dataSource.reload(); }); } } } 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.js'; ReactDOM.render( <App />, document.getElementById('app') );
<!DOCTYPE html> <html> <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/19.2.3/css/dx.common.css" /> <link rel="stylesheet" type="text/css" href="https://cdn3.devexpress.com/jslib/19.2.3/css/dx.light.css" /> <link rel="stylesheet" type="text/css" href="styles.css" /> <script src="https://unpkg.com/core-js@2.4.1/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.js'); </script> </head> <body class="dx-viewport"> <div class="demo-container"> <div id="app"></div> </div> </body> </html>
#chart { height: 440px; }
System.config({ transpiler: 'plugin-babel', paths: { 'npm:': 'https://unpkg.com/' }, defaultExtension: 'js', map: { 'react': 'npm:react@16/umd/react.development.js', 'react-dom': 'npm:react-dom@16/umd/react-dom.development.js', 'prop-types': 'npm:prop-types/prop-types.js', 'devextreme': 'npm:devextreme@19.2', 'devextreme-react': 'npm:devextreme-react@19.2', 'jszip': 'npm:jszip@3.1.3/dist/jszip.min.js', 'whatwg-fetch': 'npm:whatwg-fetch@2.0.4/fetch.js', 'quill': 'npm:quill@1.3.7/dist/quill.js', 'devexpress-diagram': 'npm:devexpress-diagram', 'devexpress-gantt': 'npm:devexpress-gantt', // SystemJS plugins 'plugin-babel': 'npm:systemjs-plugin-babel@0/plugin-babel.js', 'systemjs-babel-build': 'npm:systemjs-plugin-babel@0/systemjs-babel-browser.js' }, packages: { 'devextreme-react': { main: 'index.js' }, 'devextreme': { defaultExtension: 'js' } }, babelOptions: { sourceMaps: false, stage0: true, react: true } });