The code to accomplish this uses the esri.tasks.StatisticDefinition class (new at ArcGIS API for JavaScript version 2.6) to get the maximum for a particlar field of a layer in a map service. Other statistics that can be returned by the map service are: minimum, sum, count, average and standard deviation
<!DOCTYPE html> <html> <head> <meta charset="utf-8"> <meta name="viewport" content="initial-scale=1, maximum-scale=1,user-scalable=no"> <title>Query statistics</title> <link rel="stylesheet" href="https://js.arcgis.com/3.29/dijit/themes/tundra/tundra.css"> <link rel="stylesheet" href="https://js.arcgis.com/3.29/esri/css/esri.css"> <style> html, body { height: 100%; width: 100%; margin: 0; padding: 0; } #map{ margin: 0; padding: 0; } #feedback { position: absolute; height: 330px; font-family: arial; margin: 5px; padding: 5px; z-index: 40; background: #fff; color: #444; width: 300px; right: 30px; bottom: 30px; -moz-box-shadow: 0 0 5px #888; -webkit-box-shadow: 0 0 5px #888; box-shadow: 0 0 5px #888; } #county { padding: 5px 0 0 0; font-weight: 700; } h3 { margin: 0 0 5px 0; border-bottom: 1px solid #444; } </style> <script>var dojoConfig = { parseOnLoad: true };</script> <script src="https://js.arcgis.com/3.29/"></script> <script> dojo.require("dijit.layout.BorderContainer"); dojo.require("dijit.layout.ContentPane"); dojo.require("dojox.widget.AnalogGauge"); dojo.require("dojox.widget.gauge.AnalogArcIndicator"); dojo.require("esri.map"); dojo.require("esri.tasks.query"); dojo.require("esri.layers.FeatureLayer"); var app = {}; app.abbrLookup = { "Maine": "ME", "Vermont": "VT", "New Hampshire": "NH", "Connecticut": "CT", "Massachusetts": "MA", "Rhode Island": "RI" }; function init() { app.map = new esri.Map("map", { basemap: "oceans", center: [-70.324, 44.256], zoom: 7 }); var countiesUrl = "https://sampleserver6.arcgisonline.com/arcgis/rest/services/Census/MapServer/2"; var stateList = "'Maine', 'New Hampshire', 'Vermont', 'Connecticut', 'Massachusetts', 'Rhode Island'"; var newEnglandDef = dojo.string.substitute("STATE_NAME IN (${0})", [stateList]); var outFields = ["POP2007", "STATE_NAME", "NAME"]; var outline = new esri.symbol.SimpleLineSymbol() .setColor(dojo.colorFromHex("#fff")); app.sym = new esri.symbol.SimpleFillSymbol() .setColor(new dojo.Color([52, 67, 83, 0.4])) .setOutline(outline); var renderer = new esri.renderer.SimpleRenderer(app.sym); var hColor = dojo.colorFromHex("#ff3"); var hOutline = new esri.symbol.SimpleLineSymbol() .setColor(hColor).setWidth(4); app.highlight = new esri.symbol.SimpleFillSymbol() .setColor(new dojo.Color([0, 0, 0, 0])) .setOutline(hOutline); // use new 10.1 query statistic definition to find // the value for the most populous county in New England var popQueryTask = new esri.tasks.QueryTask(countiesUrl); var popQuery = new esri.tasks.Query(); var statDef = new esri.tasks.StatisticDefinition(); statDef.statisticType = "max"; statDef.onStatisticField = "POP2007"; statDef.outStatisticFieldName = "maxPop"; popQuery.returnGeometry = false; popQuery.where = newEnglandDef; popQuery.outFields = outFields; popQuery.outStatistics = [ statDef ]; popQueryTask.execute(popQuery, handlePopQuery); // create a feature layer for counties in New England app.neCounties = new esri.layers.FeatureLayer(countiesUrl, { "id": "NewEngland", "mode": esri.layers.FeatureLayer.MODE_ONDEMAND, "outFields": outFields }); // set a definition expression so only counties in New England are shown app.neCounties.setDefinitionExpression(newEnglandDef); app.neCounties.setRenderer(renderer); dojo.connect(app.neCounties, "onMouseOver", showInfo); app.map.addLayer(app.neCounties); // create the gauge createGauge(dojo.byId("gauge"), 0); } function showInfo(evt) { app.map.graphics.clear(); app.map.graphics.add( new esri.Graphic( evt.graphic.geometry, app.highlight ) ); updateGauge(evt.graphic); } function createGauge(gdiv, startValue) { var indicator = new dojox.widget.gauge.AnalogArcIndicator({ interactionMode: "gauge", noChange: false, value: startValue, width: 20, offset: 65, color: "#ff3", title: "value", hideValue: true, duration: 100 // default is 1000 }); app.gauge = new dojox.widget.AnalogGauge({ background: [200, 200, 200, 0.0], width: parseInt(gdiv.style.width, 10), height: parseInt(gdiv.style.height, 10), cx: parseInt(gdiv.style.width, 10) / 2, cy: parseInt(gdiv.style.height, 10) * 0.75, style: "position: absolute;", radius: parseInt(gdiv.style.width, 10) / 2, useTooltip: false, ranges: [{ low: 0, high: 100, color: "rgba(255,0,0,0)" }], majorTicks: { offset: 90, interval: 25, length: 3, color: 'black' }, indicators: [ indicator ] }, dojo.create("div", null, gdiv)); app.gauge.startup(); // add percent label app.percentDiv = dojo.create("div",{ "innerHTML": "0%", "style": { "position": "absolute", "bottom": app.gauge.height - app.gauge.cy + "px", "left": "-1000px", "font-family": "verdana", "font-size": "24px", "color":"#000" } }); dojo.place(app.percentDiv, app.gauge.domNode); // put the percent label in the middle of the gauge var contentBox = dojo.contentBox(app.percentDiv); dojo.style(app.percentDiv, "left", app.gauge.cx + "px"); dojo.style(app.percentDiv, "marginLeft", (-contentBox.w/2) + "px"); if( app.gauge.cx ) { dojo.style(app.percentDiv, "marginBottom", (-contentBox.h/2) + "px"); } } function updateGauge(g) { dojo.byId("county").innerHTML = "Highlighted: " + g.attributes.NAME + " County, " + app.abbrLookup[g.attributes.STATE_NAME] + "<br />" + "Population(2007): " + dojo.number.format(g.attributes.POP2007); var perc = parseInt((g.attributes.POP2007 / app.maxPop) * 100, 10); app.percentDiv.innerHTML = perc + "%"; app.gauge.indicators[0].update(perc); } function handlePopQuery(result) { console.log('pop query...', result); app.maxPop = result.features[0].attributes.maxPop; } dojo.ready(init); </script> </head> <body class="tundra"> <div data-dojo-type="dijit.layout.BorderContainer" data-dojo-props="design:'headline',gutters:false" style="width: 100%; height: 100%; margin: 0;"> <div id="map" data-dojo-type="dijit.layout.ContentPane" data-dojo-props="region:'center'"> <div id="feedback"> <h3>County Info</h3> <div id="info"> Mouse over to see how a particular county's population compares to the most populous county in New England (Middlesex, MA). </div> <div id="county">...county name here...</div> <div id="gauge" style="position:absolute; width: 290px; height: 230px;"></div> </div> </div> </div> </body> </html>