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Charts

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. 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.

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<template> <DxChart id="chart" ref="chart" :data-source="chartDataSource" title="Temperature in Toronto (2017)" > <DxZoomAndPan argument-axis="pan"/> <DxScrollBar :visible="true"/> <DxArgumentAxis v-model:visual-range="currentVisualRange" :whole-range="bounds" argument-type="datetime" visual-range-update-mode="keep" /> <DxValueAxis :allow-decimals="false" name="temperature" > <DxTitle text="Temperature, &deg;C"> <DxFont color="#ff950c"/> </DxTitle> <DxLabel> <DxFont color="#ff950c"/> </DxLabel> </DxValueAxis> <DxSeries color="#ff950c" type="rangearea" argument-field="date" range-value1-field="minTemp" range-value2-field="maxTemp" name="Temperature range" /> <DxAnimation :enabled="false"/> <DxLoadingIndicator background-color="none"> <DxFont :size="14"/> </DxLoadingIndicator> <DxLegend :visible="false"/> </DxChart> </template> <script> import DxChart, { DxZoomAndPan, DxScrollBar, DxArgumentAxis, DxSeries, DxValueAxis, DxTitle, DxLabel, DxFont, DxAnimation, DxLoadingIndicator, DxLegend, } from 'devextreme-vue/chart'; import DataSource from 'devextreme/data/data_source'; import 'whatwg-fetch'; let packetsLock = 0; const HALFDAY = 43200000; export default { components: { DxChart, DxZoomAndPan, DxScrollBar, DxArgumentAxis, DxSeries, DxValueAxis, DxTitle, DxLabel, DxFont, DxAnimation, DxLoadingIndicator, DxLegend, }, data() { return { visualRange: { startValue: new Date(2017, 3, 1), endValue: new Date(2017, 3, 15), }, chartDataSource: new DataSource({ store: [], sort: 'date', paginate: false, }), bounds: { startValue: new Date(2017, 0, 1), endValue: new Date(2017, 11, 31), }, }; }, computed: { currentVisualRange: { get() { return this.visualRange; }, set(newRange) { const stateStart = this.visualRange.startValue; const currentStart = newRange.startValue; if (stateStart.valueOf() !== currentStart.valueOf()) { this.visualRange = newRange; } this.onVisualRangeChanged(); }, }, }, methods: { onVisualRangeChanged() { const component = this.$refs.chart.instance; const items = component.getDataSource().items(); if (!items.length || items[0].date - this.visualRange.startValue >= HALFDAY || this.visualRange.endValue - items[items.length - 1].date >= HALFDAY) { this.uploadDataByVisualRange(this.visualRange, component); } }, uploadDataByVisualRange(visualRange, component) { const dataSource = component.getDataSource(); const storage = dataSource.items(); const ajaxArgs = { startVisible: this.getDateString(visualRange.startValue), endVisible: this.getDateString(visualRange.endValue), startBound: this.getDateString(storage.length ? storage[0].date : null), endBound: this.getDateString(storage.length ? storage[storage.length - 1].date : null), }; if (ajaxArgs.startVisible !== ajaxArgs.startBound && ajaxArgs.endVisible !== ajaxArgs.endBound && !packetsLock) { packetsLock += 1; component.showLoadingIndicator(); this.getDataFrame(ajaxArgs) .then((dataFrame) => { packetsLock -= 1; const componentStorage = dataSource.store(); dataFrame .map((i) => ({ date: new Date(i.Date), minTemp: i.MinTemp, maxTemp: i.MaxTemp, })) .forEach((item) => componentStorage.insert(item)); dataSource.reload(); this.onVisualRangeChanged(); }) .catch(() => { packetsLock -= 1; dataSource.reload(); }); } }, getDataFrame(args) { let params = '?'; params += `startVisible=${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()); }, getDateString(dateTime) { return dateTime ? dateTime.toLocaleDateString('en-US') : ''; }, }, }; </script> <style> #chart { height: 440px; } </style>
import { createApp } from 'vue'; import App from './App.vue'; createApp(App).mount('#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/22.1.4/css/dx.common.css" /> <link rel="stylesheet" type="text/css" href="https://cdn3.devexpress.com/jslib/22.1.4/css/dx.light.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>
window.config = { transpiler: 'plugin-babel', meta: { '*.vue': { loader: 'vue-loader', }, 'devextreme/localization.js': { 'esModule': true, }, }, paths: { 'npm:': 'https://unpkg.com/', }, map: { 'vue': 'npm:vue@3.0.0/dist/vue.esm-browser.js', 'vue-loader': 'npm:dx-systemjs-vue-browser@1.0.15/index.js', 'whatwg-fetch': 'npm:whatwg-fetch@2.0.4/fetch.js', 'mitt': 'npm:mitt/dist/mitt.umd.js', 'rrule': 'npm:rrule@2.6.4/dist/es5/rrule.js', 'luxon': 'npm:luxon@1.28.0/build/global/luxon.min.js', 'es6-object-assign': 'npm:es6-object-assign@1.1.0', 'devextreme': 'npm:devextreme@22.1.4/cjs', 'devextreme-vue': 'npm:devextreme-vue@22.1.4', 'jszip': 'npm:jszip@3.7.1/dist/jszip.min.js', 'devextreme-quill': 'npm:devextreme-quill@1.5.16/dist/dx-quill.min.js', 'devexpress-diagram': 'npm:devexpress-diagram@2.1.63/dist/dx-diagram.js', 'devexpress-gantt': 'npm:devexpress-gantt@4.1.32/dist/dx-gantt.js', '@devextreme/runtime': 'npm:@devextreme/runtime@3.0.7', 'inferno': 'npm:inferno@7.4.4/dist/inferno.min.js', 'inferno-compat': 'npm:inferno-compat@7.4.11/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@7.4.11/dist/inferno-clone-vnode.min.js', 'inferno-create-class': 'npm:inferno-create-class@7.4.11/dist/inferno-create-class.min.js', 'inferno-extras': 'npm:inferno-extras@7.4.11/dist/inferno-extras.min.js', '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', }, packages: { 'devextreme-vue': { main: 'index.js', }, 'devextreme': { defaultExtension: 'js', }, 'devextreme/events/utils': { main: 'index', }, 'devextreme/events': { main: 'index', }, 'es6-object-assign': { main: './index.js', defaultExtension: 'js', }, }, packageConfigPaths: [ 'npm:@devextreme/*/package.json', 'npm:@devextreme/runtime@3.0.7/inferno/package.json', ], babelOptions: { sourceMaps: false, stage0: true, }, }; System.config(window.config);