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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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<template> <dx-chart id="chart" ref="chart" :data-source="chartDataSource" title="Temperature in Toronto (2017)" > <dx-zoom-and-pan argument-axis="pan"/> <dx-scroll-bar :visible="true"/> <dx-argument-axis :visual-range.sync="currentVisualRange" :whole-range="bounds" argument-type="datetime" visual-range-update-mode="keep" /> <dx-value-axis :allow-decimals="false" name="temperature" > <dx-title text="Temperature, &deg;C"> <dx-font color="#ff950c"/> </dx-title> <dx-label> <dx-font color="#ff950c"/> </dx-label> </dx-value-axis> <dx-series color="#ff950c" type="rangeArea" argument-field="date" range-value1-field="minTemp" range-value2-field="maxTemp" name="Temperature range" /> <dx-animation :enabled="false"/> <dx-loading-indicator background-color="none"> <dx-font :size="14"/> </dx-loading-indicator> <dx-legend :visible="false"/> </dx-chart> </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() { const chartDataSource = new DataSource({ store: [], sort: 'date', paginate: false }); let visualRange = { startValue: new Date(2017, 3, 1), endValue: new Date(2017, 3, 15) }; return { visualRange, chartDataSource, bounds: { startValue: new Date(2017, 0, 1), endValue: new Date(2017, 11, 31) } }; }, computed: { currentVisualRange: { get: function() { return this.visualRange; }, set: function(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.$refs.chart.instance; const items = component.getDataSource().items(); if(!items.length || items[0].date - this.visualRange.startValue >= HALFDAY || this.visualRange.endValue - items[items.length - 1].date >= HALFDAY) { this.uploadDataByVisualRange(this.visualRange, component); } }, uploadDataByVisualRange(visualRange, component) { const dataSource = component.getDataSource(); const storage = dataSource.items(); const ajaxArgs = { startVisible: this.getDateString(visualRange.startValue), endVisible: this.getDateString(visualRange.endValue), startBound: this.getDateString(storage.length ? storage[0].date : null), endBound: this.getDateString(storage.length ? storage[storage.length - 1].date : null) }; if(ajaxArgs.startVisible !== ajaxArgs.startBound && ajaxArgs.endVisible !== ajaxArgs.endBound && !packetsLock) { packetsLock++; component.showLoadingIndicator(); this.getDataFrame(ajaxArgs) .then(dataFrame => { packetsLock--; dataFrame = dataFrame.map(i => { return { date: new Date(i.Date), minTemp: i.MinTemp, maxTemp: i.MaxTemp }; }); const componentStorage = dataSource.store(); dataFrame.forEach(item => componentStorage.insert(item)); dataSource.reload(); this.onVisualRangeChanged(); }) .catch(() => { packetsLock--; dataSource.reload(); }); } }, getDataFrame(args) { let params = '?'; params += `startVisible=${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 Vue from 'vue'; import App from './App.vue'; new Vue({ el: '#app', components: { App }, template: '<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/19.1.6/css/dx.common.css" /> <link rel="stylesheet" type="text/css" href="https://cdn3.devexpress.com/jslib/19.1.6/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"> <span v-if="false">Loading...</span> </div> </div> </body> </html>
System.config({ transpiler: 'plugin-babel', paths: { 'npm:': 'https://unpkg.com/' }, map: { vue: 'npm:vue@2.6.3/dist/vue.esm.browser.js', 'vue-loader': 'npm:systemjs-vue-browser@latest/index.js', 'devextreme': 'npm:devextreme@19.1', 'devextreme-vue': 'npm:devextreme-vue@19.1', jszip: 'npm:jszip@3.1.3/dist/jszip.min.js', 'whatwg-fetch': 'npm:whatwg-fetch@2.0.4/fetch.js', 'quill': 'npm:quill@1.3.6/dist/quill.js', 'devexpress-diagram': 'npm:devexpress-diagram', 'plugin-babel': 'npm:systemjs-plugin-babel@0/plugin-babel.js', 'systemjs-babel-build': 'npm:systemjs-plugin-babel@0/systemjs-babel-browser.js' }, meta: { '*.vue': { loader: 'vue-loader' } }, packages: { 'devextreme-vue': { main: 'index.js' }, 'devextreme': { defaultExtension: 'js' } }, babelOptions: { sourceMaps: false, stage0: true } });