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, °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/19.2.4/css/dx.common.css" />
<link rel="stylesheet" type="text/css" href="https://cdn3.devexpress.com/jslib/19.2.4/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
}
});