Style a feature layer | OpenLayers

Learn how to use style feature layers.

Style a feature layer using API key authentication

A feature layer is a dataset in a feature service hosted in ArcGIS. Each feature layer contains features with a single geometry type (point, line, or polygon), and a set of attributes. Layers in OpenLayers can contain style functions, which use attribute values to change the appearance of features. This allows you to create complex, data-driven visualizations by relating visual variables to data attributes.

In this tutorial, you apply different styles to enhance the visualization of the Trailheads, Trails and Parks and Open Spaces feature layers.

Prerequisites

You need an ArcGIS Location Platform or ArcGIS Online account.

Steps

Get the starter app

Select a type of authentication and follow the steps to create a new app.

Choose API key authentication if you:

Want the easiest way to get started.
Want to build public applications that access ArcGIS Location Services and secure items.
Have an ArcGIS Location Platform or ArcGIS Online account.

Choose user authentication if you:

Want to build private applications.
Require application users to sign in with their own ArcGIS account and access resources their behalf.
Have an ArcGIS Online account.

To learn more about both types of authentication, go to Authentication.

You can choose one of the following to create a new CodePen:

Option 1: Complete the Display a map tutorial; or,
Option 2: Start from the Display a map tutorial .

Set up authentication

Create a new API key credential with the correct privileges to get an access token.

Go to the Create an API key tutorial and create an API key with the following privilege(s):
- Privileges
  - Location services > Basemaps
- Item access
  - Note: If you are using your own custom data layer for this tutorial, you need to grant the API key credentials access to the layer item. Learn more in Item access privileges.

Set developer credentials

Use the API key or OAuth developer credentials so your application can access ArcGIS services.

Update the accessToken variable to use your API key.

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    /* Use for API key authentication */
    const accessToken = "YOUR_ACCESS_TOKEN";
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In both the index.html and callback.html files, replace YOUR_CLIENT_ID and YOUR_REDIRECT_URL with the client ID and redirect URL of your OAuth credentials.

index.html
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    /* Use for user authentication */
    const clientId = "YOUR_CLIENT_ID"; // Your client ID from OAuth credentials
    const redirectUri = ""YOUR_REDIRECT_URI""; // The redirect URL registered in your OAuth credentials
    const session = await arcgisRest.ArcGISIdentityManager.beginOAuth2({
      clientId,
      redirectUri,
      portal: "https://www.arcgis.com/sharing/rest" // Your portal URL
    });

    const accessToken = session.token;

callback.html
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    arcgisRest.ArcGISIdentityManager.completeOAuth2({
      clientId: "YOUR_CLIENT_ID", // Your client ID from OAuth credentials
      redirectUri: "YOUR_REDIRECT_URI", // The redirect URL registered in your OAuth credentials
      portal: "https://www.arcgis.com/sharing/rest" // Your portal URL
    });

Run the app and ensure you can sign in successfully.

If you are unable to sign in, make sure you have the correct redirect URL and port. This URL varies based on your application and typically takes the format of https://<server>[:port]/callback.html or http://my-arcgis-app:/auth. For example, if you are running an application on http://127.0.0.1:5500/, set http://127.0.0.1:5500/callback.html as your redirect URL in the index.html and callback.html file and your developer credential. They all have to match!

Style trailheads with an image and labels

A Style in OpenLayers has several possible components: an image, text, stroke, fill and so on. To display a hiker icon for the trailheads layer, you use an Icon style as the image component. Specify which image file as the src, and the size as the scale parameter.

To display the trailhead name, you use a Text style. Use a left value for textAlign with an offsetX of 10 to display the labels to the right of the icons. Use Fill and Stroke styles as the fill and stroke properties to give the labels white text with a teal outline. The font property is a CSS font definition. Since the label for each trailhead is different, use a function to return a Style for a given feature. Set the text property using feature's TRL_NAME attribute.

Inside olms load handler, create a trailheadStyle function that takes a feature and returns a Style containing an Icon style. Use http://static.arcgis.com/images/Symbols/NPS/npsPictograph_0231b.png for the src and set a scale of 25%.

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    const basemapId = "arcgis/streets";
    const basemapURL = `https://basemapstyles-api.arcgis.com/arcgis/rest/services/styles/v2/styles/${basemapId}?token=${accessToken}`;

    olms.apply(map, basemapURL).then(function (map) {

      const trailheadStyle = function (feature) {
        return new ol.style.Style({
          image: new ol.style.Icon({
            src: "http://static.arcgis.com/images/Symbols/NPS/npsPictograph_0231b.png",
            scale: 0.25
          }),

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Add a Text style to display labels with white text, teal outline, in an italic sans-serif font. Set the text property using the feature's TRL_NAME attribute.

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      const trailheadStyle = function (feature) {
        return new ol.style.Style({
          image: new ol.style.Icon({
            src: "http://static.arcgis.com/images/Symbols/NPS/npsPictograph_0231b.png",
            scale: 0.25
          }),

          text: new ol.style.Text({
            text: feature.get("TRL_NAME"),
            font: "italic 12px sans-serif",
            offsetX: 10,
            textAlign: "left",
            fill: new ol.style.Fill({
              color: "#FFFFFF"
            }),

            stroke: new ol.style.Stroke({
              color: "#5E8D74",
              width: 3
            })
          })

        });
      };
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Add a Vector layer with a Vector source to load and display the trailheads feature layer. Set declutter to be true to prevent label overlap. Pass the trailheadsStyle function as the style property.

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            stroke: new ol.style.Stroke({
              color: "#5E8D74",
              width: 3
            })
          })

        });
      };

      const trailheadsLayerName = "Trailheads";
      const trailheadsLayerURL =
        "https://services3.arcgis.com/GVgbJbqm8hXASVYi/arcgis/rest/services/" +
        trailheadsLayerName +
        "/FeatureServer/0/query?where=1%3D1&outFields=*&returnGeometry=true&f=pgeojson";

      const trailheadsLayer = new ol.layer.Vector({
        source: new ol.source.Vector({
          format: new ol.format.GeoJSON(),
          url: trailheadsLayerURL,

        }),

        style: trailheadStyle,
        declutter: true
      });


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For more information about adding feature layers using GeoJSON, see the Add a feature layer as GeoJSON tutorial.

Add the data attribution for the feature layer source.

Go to the Trailheads (Santa Monica Mountains) item.
Scroll down to the Acknowledgments section and copy its value.

Paste the copied value to the attributions property.

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            stroke: new ol.style.Stroke({
              color: "#5E8D74",
              width: 3
            })
          })

        });
      };

      const trailheadsLayerName = "Trailheads";
      const trailheadsLayerURL =
        "https://services3.arcgis.com/GVgbJbqm8hXASVYi/arcgis/rest/services/" +
        trailheadsLayerName +
        "/FeatureServer/0/query?where=1%3D1&outFields=*&returnGeometry=true&f=pgeojson";

      const trailheadsLayer = new ol.layer.Vector({
        source: new ol.source.Vector({
          format: new ol.format.GeoJSON(),
          url: trailheadsLayerURL,

          // Attribution text retrieved from https://arcgis.com/home/item.html?id=883cedb8c9fe4524b64d47666ed234a7
          attributions: ["Los Angeles GeoHub |"]

        }),

        style: trailheadStyle,
        declutter: true
      });


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Style trail width by elevation gain

To visualize the elevation gain of a trail you can use the width of a Stroke style. To do this, create another function which returns a Style. The width of the style's stroke property will be a calculation converting feet of elevation gain to pixels of width.

Create a trailStyle function that takes a feature and returns a Style with a Stroke style. Set the color to pink, and calculate the width property from the feature's ELEV_GAIN attribute.

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        style: trailheadStyle,
        declutter: true
      });



      const trailStyle = function (feature) {
        return new ol.style.Style({
          stroke: new ol.style.Stroke({
            color: "#BA55D3",
            width: 3 + (4 * feature.get("ELEV_GAIN")) / 2300
          })
        });
      };
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Add the Trails feature layer as a Vector layer with a GeoJSON Vector source. Pass your trailStyle function as the style property.

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      const trailStyle = function (feature) {
        return new ol.style.Style({
          stroke: new ol.style.Stroke({
            color: "#BA55D3",
            width: 3 + (4 * feature.get("ELEV_GAIN")) / 2300
          })
        });
      };

      const trailsLayerName = "Trails";
      const trailsLayerURL =
        "https://services3.arcgis.com/GVgbJbqm8hXASVYi/arcgis/rest/services/" +
        trailsLayerName +
        "/FeatureServer/0/query?where=1%3D1&outFields=*&returnGeometry=true&f=pgeojson";
      const trailsLayer = new ol.layer.Vector({
        source: new ol.source.Vector({
          format: new ol.format.GeoJSON(),
          url: trailsLayerURL,

        }),

        style: trailStyle
      });

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Add the data attribution for the feature layer source.

Go to the Trails item.
Scroll down to the Acknowledgments section and copy its value.

Paste the copied value to the attributions property.

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      const trailStyle = function (feature) {
        return new ol.style.Style({
          stroke: new ol.style.Stroke({
            color: "#BA55D3",
            width: 3 + (4 * feature.get("ELEV_GAIN")) / 2300
          })
        });
      };

      const trailsLayerName = "Trails";
      const trailsLayerURL =
        "https://services3.arcgis.com/GVgbJbqm8hXASVYi/arcgis/rest/services/" +
        trailsLayerName +
        "/FeatureServer/0/query?where=1%3D1&outFields=*&returnGeometry=true&f=pgeojson";
      const trailsLayer = new ol.layer.Vector({
        source: new ol.source.Vector({
          format: new ol.format.GeoJSON(),
          url: trailsLayerURL,

          // Attribution text retrieved from https://arcgis.com/home/item.html?id=69e12682738e467eb509d8b54dc73cbd
          attributions: ["Los Angeles GeoHub |"]

        }),

        style: trailStyle
      });

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Create a bikeTrailsStyle function. If the feature has a Yes value for USE_BIKE, return a white dashed Stroke style. Otherwise, do not return a Style, so the feature will not be displayed.

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        style: trailStyle
      });


      const bikeTrailsStyle = function (feature) {
        if (feature.get("USE_BIKE") === "Yes") {
          return new ol.style.Style({

            stroke: new ol.style.Stroke({
              lineDash: [1, 4],
              color: "white",
              width: 2
            })
          });
        }
      };
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Add a bikeTrailsLayer using the source from trailsLayer, with the bikeTrailsStyle function.

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            stroke: new ol.style.Stroke({
              lineDash: [1, 4],
              color: "white",
              width: 2
            })
          });
        }
      };

      const bikeTrailsLayer = new ol.layer.Vector({
        source: trailsLayer.getSource(),
        style: bikeTrailsStyle
      });

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Style park colors by type

You can use color to communicate the category of a feature, such as the type of a park or open space. Use a style function to returns a Fill style, in which you derive the color property from the feature's TYPE property.

Create a parksStyle function which returns a Fill style. Look up the feature's TYPE attribute in a table to give a different color for Natural Areas, Regionla Open Space, Local Park and Regional Recreation Park. If the type is not one of these, make the color transparent.

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      const bikeTrailsLayer = new ol.layer.Vector({
        source: trailsLayer.getSource(),
        style: bikeTrailsStyle
      });


      const parksStyle = function (feature) {
        const colorTable = {
          "Natural Areas": "#9E559C",
          "Regional Open Space": "#A7C636",
          "Local Park": "#149ECE",
          "Regional Recreation Park": "#ED5151"
        };

        return new ol.style.Style({
          fill: new ol.style.Fill({
            color: colorTable[feature.get("TYPE")] || "transparent"
          })
        });
      };
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Create a Vector layer with a Vector source for the parks feature layer. Pass your parksStyle function as the style property, with a low opacity.

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        return new ol.style.Style({
          fill: new ol.style.Fill({
            color: colorTable[feature.get("TYPE")] || "transparent"
          })
        });
      };

      const parksLayerName = "Parks_and_Open_Space";
      const parksLayerURL =
        "https://services3.arcgis.com/GVgbJbqm8hXASVYi/arcgis/rest/services/" +
        parksLayerName +
        "/FeatureServer/0/query?where=1%3D1&outFields=*&returnGeometry=true&f=pgeojson";
      const parksLayer = new ol.layer.Vector({
        source: new ol.source.Vector({
          format: new ol.format.GeoJSON(),
          url: parksLayerURL,

        }),
        opacity: 0.2,
        style: parksStyle
      });
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Add the data attribution for the feature layer source.

Go to the Parks and Open Space item.
Scroll down to the Acknowledgments section and copy its value.

Paste the copied value to the attributions property.

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        return new ol.style.Style({
          fill: new ol.style.Fill({
            color: colorTable[feature.get("TYPE")] || "transparent"
          })
        });
      };

      const parksLayerName = "Parks_and_Open_Space";
      const parksLayerURL =
        "https://services3.arcgis.com/GVgbJbqm8hXASVYi/arcgis/rest/services/" +
        parksLayerName +
        "/FeatureServer/0/query?where=1%3D1&outFields=*&returnGeometry=true&f=pgeojson";
      const parksLayer = new ol.layer.Vector({
        source: new ol.source.Vector({
          format: new ol.format.GeoJSON(),
          url: parksLayerURL,

          // Attribution text retrieved from https://arcgis.com/home/item.html?id=f2ea5d874dad427294641d2d45097c0e
          attributions: ["Los Angeles GeoHub |"]

        }),
        opacity: 0.2,
        style: parksStyle
      });
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Add all layers to map

To display multiple layers in a specific order, you group them using a LayerGroup. This makes it easier to manage and organize your map layers. Once the group is set up, you can display on it to the map using map.addLayer().

Create a layer group to add all the layers with the correct ordering.

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      const layerGroup = new ol.layer.Group({
        layers: [parksLayer, bikeTrailsLayer, trailsLayer, trailheadsLayer]
      });

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Display the layers on the map.

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      const layerGroup = new ol.layer.Group({
        layers: [parksLayer, bikeTrailsLayer, trailsLayer, trailheadsLayer]
      });

      map.addLayer(layerGroup);
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Run the app

Run the app.

You should now see parks of different colors, beneath the trails and trailhead layers.

What's next?

Learn how to use additional location services in these tutorials:

Style vector tiles

Change the fill and outline color of vector tiles based on their attributes on the client side.

Search for an address

Find an address or place using a search box.

Find a route and directions

Find a route and directions from a start and finish location.