Style a feature layer

Learn how to use renderers to apply data-driven styling to feature layers.

A feature layer is a dataset in a hosted feature service. Each feature layer contains features with a single geometry type (point, line, or polygon), and a set of attributes. Feature layers can be styled on the client-side with a renderer. Renderers are responsible for using attribute values to apply the appropriate symbol to each feature when the layer is drawn. Renderers can be used with visual variables and expressions to create more complex, data-driven visualizations.

In this tutorial, you use three different renderers to style three hosted feature layers.

Prerequisites

You need a free ArcGIS developer account to access your dashboard and API keys. The API key must be scoped to access the services used in this tutorial.

Steps

Create a new pen

To get started, either complete the Display a map tutorial or .

Set an API key

To access ArcGIS services, you need an API key.

Go to your dashboard to get an API key.

In CodePen, set the apiKey to your key, so it can be used to access basemap layer and location services.

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esriConfig.apiKey = "YOUR_API_KEY";
const map = new Map({
  basemap: "arcgis-topographic" // Basemap layer service
});

Add modules

In the require statement, add the FeatureLayer module.

The ArcGIS API for JavaScript uses AMD modules. The require function is used to load modules so they can be used in the main function. It's important to keep the module references and function parameters in the same order.

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    require([
      "esri/config",
      "esri/Map",
      "esri/views/MapView",

      "esri/layers/FeatureLayer"

    ], function(esriConfig,Map, MapView, FeatureLayer ) {
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Style trailheads (points)

Use the SimpleRenderer, PictureMarkerSymbol, and LabelClass classes to style the points with an image, and then define label attributes to display for the Trailheads feature layer.

Create a trailheadsRenderer and define it as a simple renderer. Set the symbol property to draw a hiker image accessed from its url.

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      const view = new MapView({
        container: "viewDiv",
        map: map,
        center: [-118.80543,34.02700], //Longitude, latitude
        zoom: 13
      });

      const trailheadsRenderer = {
        "type": "simple",
        "symbol": {
          "type": "picture-marker",
          "url": "http://static.arcgis.com/images/Symbols/NPS/npsPictograph_0231b.png",
          "width": "18px",
          "height": "18px"
        }
      }
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Create a trailheadsLabels and set the symbol property to draw a label with the TRL_NAME.

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      const trailheadsRenderer = {
        "type": "simple",
        "symbol": {
          "type": "picture-marker",
          "url": "http://static.arcgis.com/images/Symbols/NPS/npsPictograph_0231b.png",
          "width": "18px",
          "height": "18px"
        }
      }

      const trailheadsLabels = {
        symbol: {
          type: "text",
          color: "#FFFFFF",
          haloColor: "#5E8D74",
          haloSize: "2px",
          font: {
            size: "12px",
            family: "Noto Sans",
            style: "italic",
            weight: "normal"
          }
        },

        labelPlacement: "above-center",
        labelExpressionInfo: {
          expression: "$feature.TRL_NAME"
        }
      };

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Create a trailheads FeatureLayer. Set the url property to access its URL endpoint. Set the renderer and labelingInfo before adding trailheads to the map. The feature layer will autocast the renderer and labelingInfo to create class instances of the objects.

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        labelPlacement: "above-center",
        labelExpressionInfo: {
          expression: "$feature.TRL_NAME"
        }
      };

      // Create the layer and set the renderer
      const trailheads = new FeatureLayer({
        url: "https://services3.arcgis.com/GVgbJbqm8hXASVYi/arcgis/rest/services/Trailheads/FeatureServer/0",
        renderer: trailheadsRenderer,
        labelingInfo: [trailheadsLabels]
      });

      map.add(trailheads);
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View hiker symbols with trailhead names.

Style trails (lines)

Use the SimpleRenderer and VisualVariable classes to style trails in the Trails feature layer. Visual variables define the attribute to use to style trails with a greater elevation gain wider compared to trails with smaller elevation changes. This is one form of data-driven visualization.

Create a trailsRenderer and define it as a simple renderer.

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      map.add(trailheads);

      // Define a unique value renderer and symbols
      const trailsRenderer = {
        type: "simple",
        symbol: {
          color: "#BA55D3",
          type: "simple-line",
          style: "solid"
        },

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In the visualVariables array, set the field to ELEV_GAIN to determine line width.

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      // Define a unique value renderer and symbols
      const trailsRenderer = {
        type: "simple",
        symbol: {
          color: "#BA55D3",
          type: "simple-line",
          style: "solid"
        },

        visualVariables: [
          {
            type: "size",
            field: "ELEV_GAIN",
            minDataValue: 0,
            maxDataValue: 2300,
            minSize: "3px",
            maxSize: "7px"
          }
        ]
      };

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Create a trails FeatureLayer. Set the url to access its URL endpoint. Set the renderer and opacity properties before adding trails to the map. The feature layer will autocast the renderer a create class instances of the object.

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        visualVariables: [
          {
            type: "size",
            field: "ELEV_GAIN",
            minDataValue: 0,
            maxDataValue: 2300,
            minSize: "3px",
            maxSize: "7px"
          }
        ]
      };

      // Create the layer and set the renderer
      const trails = new FeatureLayer({
        url: "https://services3.arcgis.com/GVgbJbqm8hXASVYi/arcgis/rest/services/Trails/FeatureServer/0",
        renderer: trailsRenderer,
        opacity: .75
      });

      // Add the layer
      map.add(trails,0);
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View trails of differing widths based on elevation gain.

Show bike-only trails (lines)

You can use a renderer and definition expression to style a subset of data from a feature layer. To style bike-only trails from the Trails feature layer, use the definiteExpression, SimpleRenderer and SimpleLineSymbol classes. The layer is added on top of the existing trails layer.

Create a bikeTrailsRenderer and define it as a simple renderer. Set the symbol to draw a line that is styled with dots in pink.

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      // Add the layer
      map.add(trails,0);

      // Add bikes only trails
      const bikeTrailsRenderer = {
        type: "simple",
        symbol: {
          type: "simple-line",
          style: "short-dot",
          color: "#FF91FF",
          width: "1px"
        }
      };
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Create a bikeTrails FeatureLayer and set the url and renderer properties. Set the definiteExpression (a SQL where clause) to access bike trails from the Trails feature layer before adding bikeTrails to the map. The feature layer will autocast the renderer a create class instances of the object

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      // Add bikes only trails
      const bikeTrailsRenderer = {
        type: "simple",
        symbol: {
          type: "simple-line",
          style: "short-dot",
          color: "#FF91FF",
          width: "1px"
        }
      };

      const bikeTrails = new FeatureLayer({
        url:
          "https://services3.arcgis.com/GVgbJbqm8hXASVYi/arcgis/rest/services/Trails/FeatureServer/0",
        renderer: bikeTrailsRenderer,
        definitionExpression: "USE_BIKE = 'YES'"
      });

      map.add(bikeTrails, 1);
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View the location of bike trails in relation to other trails.

Style open spaces (polygons)

You can use renderers to style feature layer data by unique attribute values. Use the UniqueValueRenderer and SimpleFillSymbol classes to style polygon features with different fill colors, based on the TYPE attribute in the Parks and Open Spaces feature layer.

Create a createFillSymbol function with value and color as parameters. The function will return a solid, simple-fill symbol for each park type.

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      map.add(bikeTrails, 1);

      // Add parks with a class breaks renderer and unique symbols
      function createFillSymbol(value, color) {
        return {
          "value": value,
          "symbol": {
            "color": color,
            "type": "simple-fill",
            "style": "solid",
            "outline": {
              "style": "none"
            }
          },
          "label": value
        };
      }

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Create an openSpacesRenderer and define it as unique-value. Set the field property to TYPE. In the uniqueValueInfos array, set unique colors for each park type.

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      // Add parks with a class breaks renderer and unique symbols
      function createFillSymbol(value, color) {
        return {
          "value": value,
          "symbol": {
            "color": color,
            "type": "simple-fill",
            "style": "solid",
            "outline": {
              "style": "none"
            }
          },
          "label": value
        };
      }

      const openSpacesRenderer = {
        type: "unique-value",
        field: "TYPE",
        uniqueValueInfos: [
          createFillSymbol("Natural Areas", "#9E559C"),
          createFillSymbol("Regional Open Space", "#A7C636"),
          createFillSymbol("Local Park", "#149ECE"),
          createFillSymbol("Regional Recreation Park", "#ED5151")
        ]
      };

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Create an openspaces FeatureLayer. Set the url to access its URL endpoint. Set the renderer and opacity properties before adding openspacesto the map. The feature layer will autocast the renderer a create class instances of the object

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      const openSpacesRenderer = {
        type: "unique-value",
        field: "TYPE",
        uniqueValueInfos: [
          createFillSymbol("Natural Areas", "#9E559C"),
          createFillSymbol("Regional Open Space", "#A7C636"),
          createFillSymbol("Local Park", "#149ECE"),
          createFillSymbol("Regional Recreation Park", "#ED5151")
        ]
      };

      // Create the layer and set the renderer
      const openspaces = new FeatureLayer({
        url: "https://services3.arcgis.com/GVgbJbqm8hXASVYi/arcgis/rest/services/Parks_and_Open_Space/FeatureServer/0",
        renderer: openSpacesRenderer,
        opacity: 0.2
      });

      // Add the layer
      map.add(openspaces,0);
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Run the app

In CodePen, run your code to display the map.

The completed map should display all of the layers with a unique, data-driven style.

What's next?

Learn how to use additional API features and ArcGIS services in these tutorials:

ArcGIS API for JavaScript

Style a feature layer

Solution

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