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Showing content from https://developers.arcgis.com/maplibre-gl-js/styles-and-data-visualization/style-a-feature-layer/ below:

Style a feature layer | MapLibre GL JS

Learn how to use style a feature layer.

Style a feature layer using API key authentication Style a feature layer using user 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. A feature layer can be styled in MapLibre GL JS with a layer connected to a GeoJSON source. Layers can contain expressions which use attribute values to calculate values. This lets you create complex, data-driven visualizations by relating visual variables to data attributes.

In this tutorial, you use symbol, line and fill layers to style three hosted feature layers in ArcGIS.

Mapping and location services guide

To learn more about styling layers, go to Data visualization.

Prerequisites

An ArcGIS Location Platform or ArcGIS Online account.

Steps Get the starter app

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

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 .

Go to the Display a map tutorial and download the solution.
Unzip the folder and open it in a text editor of your choice, such as Visual Studio Code. The starter app includes the following:
- callback.html: This contains callback as part of the authentication process.
- index.html: This contains app logic and the OAuth 2.0 code necessary to perform the authentication.

Set up authentication

Create developer credentials in your portal for the type of authentication you selected.

Create a new API key credential with the correct privileges to access the resources used in this tutorial.

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.
Copy the API key access token to your clipboard when prompted.

Create a new OAuth credential to register the application.

Go to the Create OAuth credentials for user authentication tutorial to create an OAuth credential.
Copy the Client ID and Redirect URL from your OAuth credentials item and paste them to a safe location. They will be used in a later step.

Note

To use this application, users must have an ArcGIS account with the necessary privileges to access all resources and services.

Set developer credentials

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

Update the accessToken variable to use your API key.

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    /* Use for API key authentication */
    const accessToken = "YOUR_ACCESS_TOKEN"

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;

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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!

Load a hiker icon

To use an image as an icon, you must first load the image into the map style using map.loadImage and map.addImage.

Call map.loadImage with 'https://static.arcgis.com/images/Symbols/NPS/npsPictograph_0231b.png' as the first parameter. The second parameter is a callback taking an error and the image.

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    const map = new maplibregl.Map({
      container: "map", // the id of the div element
      style: `https://basemapstyles-api.arcgis.com/arcgis/rest/services/styles/v2/styles/${basemapEnum}?token=${accessToken}`,
      zoom: 12, // starting zoom
      center: [-118.805, 34.027] // starting location [longitude, latitude]
    });

    map.loadImage("https://static.arcgis.com/images/Symbols/NPS/npsPictograph_0231b.png").then((resp) => {

    });

Call map.addImage to define hiker-icon as the provided image.

A MapLibre style can contain a number of images as part of its sprite file. map.addImage is required to display images that are not included in its sprite file.

See the MapLibre GL JS documentation for more information.

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    map.loadImage("https://static.arcgis.com/images/Symbols/NPS/npsPictograph_0231b.png").then((resp) => {

      map.addImage("hiker-icon", resp.data);

    });

Style and display trailheads with a hiker icon and labels

To display an icon of a hiker for each trailhead, along with a label, you can use a single symbol layer. Properties for the label start with text- and properties for the icon start with icon-.

Create a function called showTrailheads. Inside, add a GeoJSON source.

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    map.loadImage("https://static.arcgis.com/images/Symbols/NPS/npsPictograph_0231b.png").then((resp) => {

      map.addImage("hiker-icon", resp.data);

    });

    function showTrailheads() {

      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";
      map.addSource("trailheads", {
        type: "geojson",
        data: trailheadsLayerURL,

      });

    }

Add the data attribution for the feature layer source.

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

Create an attribution property and paste the attribution value from the item.

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    map.loadImage("https://static.arcgis.com/images/Symbols/NPS/npsPictograph_0231b.png").then((resp) => {

      map.addImage("hiker-icon", resp.data);

    });

    function showTrailheads() {

      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";
      map.addSource("trailheads", {
        type: "geojson",
        data: trailheadsLayerURL,

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

      });

    }

Note

To learn how to get attribution from an item, go to Esri and data attribution.

Add a symbol layer for the hiker icons. Use icon-image to reference the icon you loaded.

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    function showTrailheads() {

      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";
      map.addSource("trailheads", {
        type: "geojson",
        data: trailheadsLayerURL,

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

      });

      map.addLayer({
        id: "trailheads-symbol",
        type: "symbol",
        source: "trailheads",
        layout: {
          "icon-image": "hiker-icon",
          "icon-size": 0.3,
          "icon-allow-overlap": true,

        }
      });

    }

Add additional label properties. Set a text-anchor of bottom, with a text-offset of [0, -2] to position the label above the icon. Use the TRL_NAME attribute as the text field.

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      map.addLayer({
        id: "trailheads-symbol",
        type: "symbol",
        source: "trailheads",
        layout: {
          "icon-image": "hiker-icon",
          "icon-size": 0.3,
          "icon-allow-overlap": true,

          "text-font": ["Arial Italic"],
          "text-field": ["get", "TRL_NAME"],
          "text-size": 12,
          "text-anchor": "bottom",
          "text-offset": [0, -2]

        },
        paint: {
          "text-color": "white",
          "text-halo-color": "seagreen",
          "text-halo-width": 2

        }
      });

Add a load event handler

It is important to wait for the MapLibre GL JS map to finish loading before adding any layers.

Add an event handler to the map load event. Inside, call the showTrailheads function.

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        },
        paint: {
          "text-color": "white",
          "text-halo-color": "seagreen",
          "text-halo-width": 2

        }
      });

    }

    map.on("load", () => {

      showTrailheads();

    });

At the top right, click Run to test your map. You should see icons and labels at each of the trailheads.

Style and display all trails

Create a showTrails function. Inside, add a GeoJSON source with id trails.

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        },
        paint: {
          "text-color": "white",
          "text-halo-color": "seagreen",
          "text-halo-width": 2

        }
      });

    }

    function showTrails() {

      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";
      map.addSource("trails", {
        type: "geojson",
        data: trailsLayerURL,

      });

    }

Add the data attribution for the feature layer source.

Go to the Trails item.
Scroll down to the Credits (Attribution) section and copy its value.

Create an attribution property and paste the attribution value from the item.

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        },
        paint: {
          "text-color": "white",
          "text-halo-color": "seagreen",
          "text-halo-width": 2

        }
      });

    }

    function showTrails() {

      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";
      map.addSource("trails", {
        type: "geojson",
        data: trailsLayerURL,

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

      });

    }

Note

To learn how to get attribution from an item, go to Esri and data attribution.

Add a line layer with id trails-line to display the trails source.

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    function showTrails() {

      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";
      map.addSource("trails", {
        type: "geojson",
        data: trailsLayerURL,

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

      });

      map.addLayer({
        id: "trails-line",
        type: "line",
        source: "trails",
        paint: {
          "line-color": "hsl(291, 44%, 60%)",

          "line-opacity": 0.75
        }
      });

    }

At the top right, click Run to test your map. The trails should display as purple lines.

Style trail width by elevation gain

To make the width of the trail line reflect the elevation gain, you can use a MapLibre GL expression as the value of the line-width. You use the ['interpolate'] and ['get'] expressions to achieve this.

['interpolate', ['linear'], ... creates a linear mapping from one range of input values (the number of feet of elevation gain) to a range of output values (the number of pixels of line width). You provide "stops", such as mapping 2,300 feet to 7 pixels. See the MapLibre Style Specification for details.

['get', 'ELEV_GAIN'] accesses the ELEV_GAIN property. See the MapLibre Style Specification for details.

Update the trails-line layer definition that calculates line-width from the ELEV_GAIN attribute.

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      map.addLayer({
        id: "trails-line",
        type: "line",
        source: "trails",
        paint: {
          "line-color": "hsl(291, 44%, 60%)",

          "line-width": ["interpolate", ["linear"], ["get", "ELEV_GAIN"], 0, 3, 2300, 7],

          "line-opacity": 0.75
        }
      });

At the top right, click Run to test your map. The trails should display as purple lines with varying thickness based on elevation gain.

Display bike-only trails

You can limit a layer to display only certain features by setting a filter. A filter is defined by an expression that should evaluate to true for the features you want included.

To show trails that allow bikes with a dashed line, you can create a new layer that sits above the other trails layer. You can reuse the existing source.

Create a function called showBikeTrails. Inside, add a layer with id biketrails-line. Use a filter to only show trails where USE_BIKE has a value of YES. Set line-dasharray to [1, 2] to create short dashes.

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      map.addLayer({
        id: "trails-line",
        type: "line",
        source: "trails",
        paint: {
          "line-color": "hsl(291, 44%, 60%)",

          "line-width": ["interpolate", ["linear"], ["get", "ELEV_GAIN"], 0, 3, 2300, 7],

          "line-opacity": 0.75
        }
      });

    }

    function showBikeTrails() {

      map.addLayer({
        id: "biketrails-line",
        type: "line",
        source: "trails",
        filter: ["==", ["get", "USE_BIKE"], "Yes"],
        paint: {
          "line-dasharray": [1, 2],
          "line-width": 2,
          "line-color": "hsl(300, 100%, 78.4%)"
        }
      });

    }

In the load event handler, call the showTrails and showBikeTrails functions. Add the calls before showTrailheads so that the trails layers are placed beneath the trailheads.

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    map.on("load", () => {

      showTrails();
      showBikeTrails();

      showTrailheads();

    });

At the top right, click Run to test your map. The trails should appear as dashed lines for trails that allow bikes.

Display park areas with different colors

You can use a different style for each unique attribute value in a feature layer. Use a ['match', ...] expression to display park polygons with different colors depending on the TYPE field.

A ['match', ...] expression choose between several different output values depending on the input value. See the MapLibre Style Specification for details.

Create a function called showParks. Inside, add a GeoJSON source for the parks. Give it an id of parks.

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      map.addLayer({
        id: "biketrails-line",
        type: "line",
        source: "trails",
        filter: ["==", ["get", "USE_BIKE"], "Yes"],
        paint: {
          "line-dasharray": [1, 2],
          "line-width": 2,
          "line-color": "hsl(300, 100%, 78.4%)"
        }
      });

    }

    function showParks() {

      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";
      map.addSource("parks", {
        type: "geojson",
        data: parksLayerURL,

      });

    }

Add the data attribution for the feature layer source.

Go to the Parks and Open Space item.
Scroll down to the Credits (Attribution) section and copy its value.

Create an attribution property and paste the attribution value from the item.

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      map.addLayer({
        id: "biketrails-line",
        type: "line",
        source: "trails",
        filter: ["==", ["get", "USE_BIKE"], "Yes"],
        paint: {
          "line-dasharray": [1, 2],
          "line-width": 2,
          "line-color": "hsl(300, 100%, 78.4%)"
        }
      });

    }

    function showParks() {

      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";
      map.addSource("parks", {
        type: "geojson",
        data: parksLayerURL,

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

      });

    }

Note

To learn how to get attribution from an item, go to Esri and data attribution.

Add a fill layer with id parks-fill and source parks. For the fill color, use a match expression for different TYPE values.

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    function showParks() {

      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";
      map.addSource("parks", {
        type: "geojson",
        data: parksLayerURL,

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

      });

      map.addLayer({
        id: "parks-fill",
        type: "fill",
        source: "parks",
        paint: {
          "fill-color": [
            "match",
            ["get", "TYPE"],
            "Natural Areas",
            "#9E559C",
            "Regional Open Space",
            "#A7C636",
            "Local Park",
            "#149ECE",
            "Regional Recreation Park",
            "#ED5151",
            "black"
          ],
          "fill-opacity": 0.2
        }
      });

    }

Back inside the load event handler, call the showParks functions. Place it before the other functions so that the parks layer is placed under the trails and trailheads.

Expand

Use dark colors for code blocks

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    map.on("load", () => {

      showParks();

      showTrails();
      showBikeTrails();

      showTrailheads();

    });

Run the app

Run the app.

You should now see trailheads with icons and labels, trails whose width varies by elevation, dashed lines for trails that allow bikes, and parks of different colors.

What's next?

Learn how to use additional ArcGIS Location Services in these tutorials:

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