Backend API
import React, { useState } from 'react';
import { DataSource } from 'devextreme-react/common/data';
import {
Chart,
ZoomAndPan,
ScrollBar,
ArgumentAxis,
ValueAxis,
Title,
Label,
Font,
Legend,
Series,
Animation,
LoadingIndicator,
} from 'devextreme-react/chart';
import type { ChartTypes, ChartRef } from 'devextreme-react/chart';
import type { VisualRange } from 'devextreme/common/charts';
type ChartType = ReturnType<ChartRef['instance']>;
const HALFDAY = 43200000;
let packetsLock = 0;
const chartDataSource = new DataSource({
store: [],
sort: 'date',
paginate: false,
});
const wholeRange = {
startValue: new Date(2025, 0, 1),
endValue: new Date(2025, 11, 31),
};
function App() {
const [visualRange, setVisualRange] = useState({
startValue: new Date(2025, 3, 1),
endValue: new Date(2025, 3, 15),
});
const handleChange = (e: ChartTypes.OptionChangedEvent): void => {
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 (2025)"
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, °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: VisualRange, component: ChartType): void => {
const dataSource = component.getDataSource();
const ajaxArgs = {
startVisible: getDateString(visualRange.startValue as Date),
endVisible: getDateString(visualRange.endValue as Date),
};
if (!packetsLock) {
packetsLock += 1;
component.showLoadingIndicator();
getDataFrame(ajaxArgs)
.then((dataFrame) => {
packetsLock -= 1;
const componentStorage = dataSource.store();
dataFrame
.map((i: any) => ({
date: new Date(i.Date),
minTemp: i.MinTemp,
maxTemp: i.MaxTemp,
}))
.forEach((item: any) => componentStorage.insert(item));
dataSource.reload();
onVisualRangeChanged(visualRange, component);
})
.catch(() => {
packetsLock -= 1;
dataSource.reload();
});
}
};
const onVisualRangeChanged = (visualRange: VisualRange, component: ChartType): void => {
const items = component.getDataSource().items();
if (
!items.length
|| items[0].date - (visualRange.startValue as Date)?.getTime() >= HALFDAY
|| (visualRange.endValue as Date)?.getTime() - items[items.length - 1].date >= HALFDAY
) {
uploadDataByVisualRange(visualRange, component);
}
};
function getDataFrame(args: { startVisible: string; endVisible: string }) {
let params = '?';
params += `startVisible=${args.startVisible}
&endVisible=${args.endVisible}`;
return fetch(
`https://js.devexpress.com/Demos/NetCore/api/TemperatureData${params}`,
).then((response) => response.json());
}
function getDateString(dateTime?: Date): string {
return dateTime ? dateTime.toLocaleDateString('en-US') : '';
}
export default App;
import React, { useState } from 'react';
import { DataSource } from 'devextreme-react/common/data';
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(2025, 0, 1),
endValue: new Date(2025, 11, 31),
};
function App() {
const [visualRange, setVisualRange] = useState({
startValue: new Date(2025, 3, 1),
endValue: new Date(2025, 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 (2025)"
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, °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 ajaxArgs = {
startVisible: getDateString(visualRange.startValue),
endVisible: getDateString(visualRange.endValue),
};
if (!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=${args.endVisible}`;
return fetch(`https://js.devexpress.com/Demos/NetCore/api/TemperatureData${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'),
);
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/26.1.5/css/dx.light.css" />
<link rel="stylesheet" type="text/css" href="./bundle.css" />
</head>
<body class="dx-viewport">
<div class="demo-container">
<div id="app"></div>
</div>
<script src="bundles/vendor/react.vendor.js"></script>
<script src="./bundle.js"></script>
</body>
</html>
#chart {
height: 440px;
}
To implement this functionality, do the following:
-
Configure a data source.
-
Assign a DataSource with an empty store to the Chart dataSource property.
-
Set the sort property to
date. -
Disable the paginate property to prevent data from partitioning.
-
-
Configure the Chart to support on-demand data loading.
-
Set the visualRangeUpdateMode property to
keep. -
Specify a loadingIndicator.
-
Specify the initial visualRange.
-
Implement a function that respond to user pan operations and tracks visualRange changes. If a user changed the visual range, initiate a request for additional data.
-
-
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
onVisualRangeChangedinitiates this procedure. -
The
uploadDataByVisualRangefunction analyzes the starting and ending points of the visual range and the bounds of already loaded data. If necessary, it calls thegetDataFramefunction to obtain new data points. Finally, it reloads the DataSource and saves the current visual range. -
The
getDataFrameAjax request gets the new data frame from the server.
-