Layer

Class: esri/layers/Layer
Inheritance: Layer Accessor
Since: ArcGIS API for JavaScript 4.0

The layer is the most fundamental component of a Map. It is a collection of spatial data in the form of vector graphics or raster images that represent real-world phenomena. Layers may contain discrete features that store vector data or continuous cells/pixels that store raster data.

In the case of vector-based layers, such as FeatureLayer and GraphicsLayer, each feature contained in the layer has a Geometry that allows it to be rendered as a Graphic with spatial context on the view. Features within the layer also contain data attributes that provide additional information, which may be viewed in popup windows and used for rendering the layer.

To create a layer you must use one of the subclasses of Layer or call the Layer.fromPortalItem() method. A few examples of layers include the following:

  • Roads and highways may be represented using linear features in a FeatureLayer
  • Land parcels can be displayed as polygons in a MapImageLayer
  • Satellite imagery may be displayed as tiled images in a TileLayer

Multiple layers may be added to the same map and overlaid on top of one another for visualization and analytical purposes. See Map for additional information regarding how to add layers to a map. Layers are rendered in the View with a LayerView.

In a broad sense, layers can be used for the following purposes:

  • Displaying location for geographic context
  • Querying data
  • Displaying categorical and/or numeric data
  • Analytics

All layer types inherit from Layer. To learn more about each layer type, comparing and contrasting their data sources and capabilities, see the table below.

Layers for querying, visualizing, analyzing data

Layer type Data source Data types Features Limitations
FeatureLayer ArcGIS FeatureServer/MapServer, ArcGIS portal item, or client-side graphics Points, polylines, polygons downloaded as vector graphics Client-side processing, popup templates, renderers with 2D and 3D symbols, querying, editing (in a future release) Limited number of features for display; may require large download depending on number of features
GraphicsLayer Client-side graphics Points, polylines, polygons displayed as vector graphics No geometry schema. Points, polylines and polygons may be stored in a single layer. No renderer nor popup templates; visualization and popup templates are handled on a graphic-by-graphic basis.
MapImageLayer ArcGIS MapServer,
ArcGIS portal item
Points, polylines, polygons, rasters exported in a single image May contain nested sublayers. Server-side processing of renderers, popup templates, opacity, and labels for fast display of many features. May be used to display, query, and join data in registered workspaces No editing support
SceneLayer ArcGIS SceneServer, ArcGIS portal item Point and multipatch geometries Can display a large number of features on the client. Ideal for rendering 3D features No 2D support; no editing
CSVLayer CSV file Points downloaded as vector graphics Client-side processing, popup templates, renderers with 2D and 3D symbols May require large download depending on the number of features
KMLLayer KML file (.kml, .kmz), ArcGIS portal item Points, polylines, polygons displayed as vector graphics Display KML file in a map or webmap No 3D support; requires access to utility service from ArcGIS.com or ArcGIS Enterprise
StreamLayer ArcGIS StreamServer Points downloaded as vector graphics Downloads and updates feature locations in real time N/A
ImageryLayer ArcGIS ImageServer, ArcGIS portal item Raster data exported as a single image Client-side and server-side pixel filtering and rendering; popup templates; querying N/A
ImageryTileLayer ArcGIS ImageServer, ArcGIS portal item Raster data exported as a single image Client-side and server-side rendering; popup templates N/A
GeoJSONLayer GeoJSON Points, polylines, polygons Renderers, labels, editing, popups Data must comply with the RFC 7946 specification which states that the coordinates are in SpatialReference WGS84
OGCFeatureLayer OGC API - Features Points, polylines, polygons Renderers, labels, popups Data must comply with the RFC 7946 specification which states that the coordinates are in SpatialReference WGS84
GeoRSSLayer GeoRSS feed Points, polylines, polygons No geometry schema; popup templates No 3D support; no support for renderers
MapNotesLayer ArcGIS WebMap, ArcGIS portal item Points, polylines, polygons, text Map Notes in a webmap No 3D support; Read-only
WCSLayer WCS service Raster data exported as a single image OGC specification N/A
WMSLayer WMS service,
ArcGIS portal item
Data exported as a single image OGC specification N/A
BaseDynamicLayer ArcGIS MapServer, WMS service Data exported as a single image This class may be extended to create dynamic map layers No 3D support; exported images cannot be cached in the browser
BuildingSceneLayer ArcGIS SceneServer, ArcGIS portal item Data is organized in BuildingGroupSublayers which contain BuildingComponentSublayers Visualize complex digital models of buildings and interact with its components No 2D support

Layers for providing geographic context

Layer type Data source Data types Features Limitations
TileLayer ArcGIS MapServer, ArcGIS portal item Image tiles Better performance for large datasets; querying features No editing, client-side rendering, or popup templates; some schema limitations in 3D views.
BaseTileLayer ArcGIS MapServer, ArcGIS portal item Image tiles This class may be extended to create custom tile layers No editing, client-side rendering, or popup templates; some schema limitations in 3D views.
VectorTileLayer ArcGIS portal item Points, polylines, and polygons rendered as vector tiles Features may be styled client-side and used as a tiled basemap No editing, client-side rendering, or popup templates.
IntegratedMeshLayer ArcGIS SceneServer, ArcGIS portal item Point cloud mesh integrated with imagery Displays 3D objects with a high level of detail No 2D support
ElevationLayer ArcGIS ImageServer, ArcGIS portal item Tiled elevation mesh/surface Renders elevation surfaces in 3D views No 2D support
BaseElevationLayer ArcGIS ImageServer, ArcGIS portal item Tiled elevation mesh/surface This class may be extended to create custom elevation layers No 2D support
PointCloudLayer ArcGIS SceneServer, ArcGIS portal item Point clouds (e.g. collected from LiDAR) Renderers; fast display of point clouds No 2D support
OpenStreetMapLayer OpenStreetMap tile services Image tiles Displays OpenStreetMap tiled content N/A
WMTSLayer WMTS tile services,
ArcGIS portal item
Image tiles OGC specification N/A
WebTileLayer non-ArcGIS, non-OGC, and non-OSM tile services Image tiles N/A No editing, client-side rendering, or popup templates.
BingMapsLayer Bing Spatial Data Service data Image tiles Displays Microsoft's Bing tiled content Bing Maps key is required; three map styles are supported: road, aerial, and hybrid

Other layers

Layer type Data source Data types Features Limitations
GroupLayer Any combination of other layer types N/A Combines two or more layers into a single layer N/A
See also:

Property Overview

Any properties can be set, retrieved or listened to. See the Working with Properties topic.
Show inherited properties Hide inherited properties
Name Type Summary Class
String

The name of the class.

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Extent

The full extent of the layer.

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String

The unique ID assigned to the layer.

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String

Indicates how the layer should display in the LayerList widget.

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Boolean

Indicates whether the layer's resources have loaded.

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Error

The Error object returned if an error occurred while loading.

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String

Represents the status of a load operation.

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Object[]

A list of warnings which occurred while loading.

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Number

The opacity of the layer.

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String

The title of the layer used to identify it in places such as the Legend and LayerList widgets.

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String

The layer type provides a convenient way to check the type of the layer without the need to import specific layer modules.

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Boolean

Indicates if the layer is visible in the View.

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Property Details

declaredClass Stringreadonly inherited
Since: ArcGIS API for JavaScript 4.7

The name of the class. The declared class name is formatted as esri.folder.className.

fullExtent Extentautocast

The full extent of the layer. By default, this is worldwide. This property may be used to set the extent of the view to match a layer's extent so that its features appear to fill the view. See the sample snippet below.

Example:
// Once the layer loads, set the view's extent to the layer's fullextent
layer.when(function(){
  view.extent = layer.fullExtent;
});
id String

The unique ID assigned to the layer. If not set by the developer, it is automatically generated when the layer is loaded.

listMode String

Indicates how the layer should display in the LayerList widget. The possible values are listed below.

Value Description
show The layer is visible in the table of contents.
hide The layer is hidden in the table of contents.
hide-children If the layer is a GroupLayer, BuildingSceneLayer, KMLLayer, MapImageLayer, TileLayer or WMSLayer, hide the children layers from the table of contents.

Possible Values:"show"|"hide"|"hide-children"

Default Value:show
loaded Booleanreadonly

Indicates whether the layer's resources have loaded. When true, all the properties of the object can be accessed.

Default Value:false
loadError Errorreadonly

The Error object returned if an error occurred while loading.

Default Value:null
loadStatus Stringreadonly

Represents the status of a load operation.

Value Description
not-loaded The object's resources have not loaded.
loading The object's resources are currently loading.
loaded The object's resources have loaded without errors.
failed The object's resources failed to load. See loadError for more details.

Possible Values:"not-loaded"|"loading"|"failed"|"loaded"

Default Value:not-loaded
loadWarnings Object[]readonly

A list of warnings which occurred while loading.

opacity Number

The opacity of the layer. This value can range between 1 and 0, where 0 is 100 percent transparent and 1 is completely opaque.

Default Value:1
Example:
// Makes the layer 50% transparent
layer.opacity = 0.5;
title String

The title of the layer used to identify it in places such as the Legend and LayerList widgets.

If the layer is loaded from a portal item, the title of the portal item will be used. If a layer is loaded as part of a webmap or a webscene, then the title of the layer as stored in the webmap/webscene will be used.

type Stringreadonly

The layer type provides a convenient way to check the type of the layer without the need to import specific layer modules.

Possible Values:"base-dynamic"|"base-elevation"|"base-tile"|"bing-maps"|"building-scene"|"csv"|"elevation"|"feature"|"geojson"|"geo-rss"|"graphics"|"group"|"imagery"|"imagery-tile"|"integrated-mesh"|"kml"|"map-image"|"map-notes"|"ogc-feature"|"open-street-map"|"point-cloud"|"route"|"scene"|"stream"|"tile"|"unknown"|"unsupported"|"vector-tile"|"wcs"|"web-tile"|"wms"|"wmts"

visible Boolean

Indicates if the layer is visible in the View. When false, the layer may still be added to a Map instance that is referenced in a view, but its features will not be visible in the view.

Default Value:true
Example:
// The layer is no longer visible in the view
layer.visible = false;

Method Overview

Name Return Type Summary Class

Cancels a load() operation if it is already in progress.

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Promise<LayerView>

Called by the views, such as MapView and SceneView, when the layer is added to the Map.layers collection and a layer view must be created for it.

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Destroys the layer and any associated resources (including its portalItem, if it is a property on the layer).

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Boolean

Emits an event on the instance.

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Promise<Object>

Fetches custom attribution data for the layer when it becomes available.

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Promise<Layer>

Creates a new layer instance from an ArcGIS Server URL.

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Promise<Layer>

Creates a new layer instance of the appropriate layer class from an ArcGIS Online or ArcGIS Enterprise portal item.

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Boolean

Indicates whether there is an event listener on the instance that matches the provided event name.

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Boolean

isFulfilled() may be used to verify if creating an instance of the class is fulfilled (either resolved or rejected).

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Boolean

isRejected() may be used to verify if creating an instance of the class is rejected.

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Boolean

isResolved() may be used to verify if creating an instance of the class is resolved.

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Promise

Loads the resources referenced by this class.

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Object

Registers an event handler on the instance.

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Promise

when() may be leveraged once an instance of the class is created.

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Method Details

cancelLoad()

Cancels a load() operation if it is already in progress.

createLayerView(view, options){Promise<LayerView>}

Called by the views, such as MapView and SceneView, when the layer is added to the Map.layers collection and a layer view must be created for it. This method is used internally and there is no use case for invoking it directly.

Parameters:
view *

The parent view.

options Object
optional

An object specifying additional options. See the object specification table below for the required properties of this object.

Specification:
signal AbortSignal
optional

A signal to abort the creation of the layerview.

Returns:
Type Description
Promise<LayerView> Resolves with a LayerView instance.
See also:
destroy()
Since: ArcGIS API for JavaScript 4.17

Destroys the layer and any associated resources (including its portalItem, if it is a property on the layer). The layer can no longer be used once it has been destroyed.

The destroyed layer will be removed from its parent object like Map, WebMap, WebScene, Basemap, Ground, or GroupLayer.

See also:
emit(type, event){Boolean}
Since: ArcGIS API for JavaScript 4.5

Emits an event on the instance. This method should only be used when creating subclasses of this class.

Parameters:
type String

The name of the event.

event Object
optional

The event payload.

Returns:
Type Description
Boolean true if a listener was notified
fetchAttributionData(){Promise<Object>}

Fetches custom attribution data for the layer when it becomes available.

Returns:
Type Description
Promise<Object> Resolves to an object containing custom attribution data for the layer.
fromArcGISServerUrl(params){Promise<Layer>}static

Creates a new layer instance from an ArcGIS Server URL. Depending on the URL, the returned layer type may be a FeatureLayer, TileLayer, MapImageLayer, ImageryLayer, ImageryTileLayer, SceneLayer, StreamLayer, IntegratedMeshLayer, PointCloudLayer, BuildingSceneLayer, ElevationLayer or GroupLayer.

This is useful when you work with various ArcGIS Server URLs, but you don't necessarily know which layer type(s) they create. This method creates the appropriate layer type for you. In case of a feature service or a scene service, when the URL points to the service and the service has multiple layers, the returned promise will resolve to a GroupLayer.

Beginning with version 4.17, it is possible to load tables from hosted feature services. This only applies to feature layers, and will successfully load if FeatureLayer.isTable returns true.

The following table details what is returned when loading specific URL types.

URL Returns
Feature service with one layer FeatureLayer where isTable returns false.
Feature service with one table FeatureLayer where isTable returns true.
Feature service with more than one layer(s)/table(s) GroupLayer with layers and tables.
Layers with type other than "Feature Layer" are discarded, e.g. Utility Network Layers N/A
Parameters:
Specification:
params Object

Input parameters for creating the layer.

Specification:
url String

The ArcGIS Server URL used to create the layer.

properties Object
optional

Set any of the layer's properties here for constructing the layer instance (e.g. popupTemplate, renderer, etc.).

Returns:
Type Description
Promise<Layer> Returns a promise that resolves to the new Layer instance.
See also:
Examples:
// This snippet shows how to add a feature layer from an ArcGIS Server URL
// Get an ArcGIS Server URL from a custom function
const arcgisUrl = getLayerUrl();

Layer.fromArcGISServerUrl({
  url: arcgisUrl,
  properties: {
    // set any layer properties here
    popupTemplate: new PopupTemplate()
  }
}).then(function(layer){
  // add the layer to the map
  map.add(layer);
});
// This snippet shows how to add a table from an ArcGIS Server URL
// Get an ArcGIS Server URL from a custom function
const arcgisUrl = getLayerUrl();

Layer.fromArcGISServerUrl({
  url: arcgisUrl
}).then(function(layer){
  // Load the table before it can be used
  layer.load().then(function() {
    // Check that it is the right type
    if (layer.isTable) {
      // Add table to map's tables collection
      map.tables.add(layer);
    }
  });
});
fromPortalItem(params){Promise<Layer>}static

Creates a new layer instance of the appropriate layer class from an ArcGIS Online or ArcGIS Enterprise portal item. If the item points to a feature service with multiple layers, then a GroupLayer is created. If the item points to a service with a single layer, then it resolves to a layer of the same type of class as the service.

Beginning with version 4.17, it is possible to load tables from feature service items hosted in ArcGIS Online and ArcGIS Enterprise. This only applies to feature layers, and will successfully load if FeatureLayer.isTable returns true.

The following table details what is returned when loading specific item types.

Item(s) Returns
Feature service with one layer FeatureLayer where isTable returns false.
Feature service with one table FeatureLayer where isTable returns true.
Feature service with more than one layer(s)/table(s) GroupLayer with layers and tables.
Feature collection with one layer FeatureLayer where isTable returns false.
Feature collection with one table FeatureLayer where isTable returns true.
Feature collection with more than one layer(s)/table(s) GroupLayer with layers and tables.
Parameters:
params Object

The parameters for loading the portal item.

Specification:
portalItem PortalItem

The object representing an ArcGIS Online or ArcGIS Enterprise portal item from which to load the layer.

Returns:
Type Description
Promise<Layer> Returns a promise which resolves to the new layer instance.
See also:
Examples:
// Create a layer from a specified portal item and add to the map
Layer.fromPortalItem({
  portalItem: {  // autocasts new PortalItem()
    id: "8444e275037549c1acab02d2626daaee"
  }
}).then(function(layer){
  // add the layer to the map
  map.add(layer);
});
// Create a table from a specified portal item and add it to the map's tables collection
Layer.fromPortalItem({
  portalItem: { // autocasts new PortalItem()
    id: "123f4410054b43d7a0bacc1533ceb8dc" // This is a hosted table stored in a feature service
  }
}).then(function(layer) {
  // Necessary to load the table in order for it to be read correctly
  layer.load().then(function() {
    // Confirm this reads as a table
    if (layer.isTable) {
      // Add the new table to the map's table collection
      map.tables.add(layer);
    }
  });
});
hasEventListener(type){Boolean}

Indicates whether there is an event listener on the instance that matches the provided event name.

Parameter:
type String

The name of the event.

Returns:
Type Description
Boolean Returns true if the class supports the input event.
isFulfilled(){Boolean}

isFulfilled() may be used to verify if creating an instance of the class is fulfilled (either resolved or rejected). If it is fulfilled, true will be returned.

Returns:
Type Description
Boolean Indicates whether creating an instance of the class has been fulfilled (either resolved or rejected).
isRejected(){Boolean}

isRejected() may be used to verify if creating an instance of the class is rejected. If it is rejected, true will be returned.

Returns:
Type Description
Boolean Indicates whether creating an instance of the class has been rejected.
isResolved(){Boolean}

isResolved() may be used to verify if creating an instance of the class is resolved. If it is resolved, true will be returned.

Returns:
Type Description
Boolean Indicates whether creating an instance of the class has been resolved.
load(signal){Promise}

Loads the resources referenced by this class. This method automatically executes for a View and all of the resources it references in Map if the view is constructed with a map instance.

This method must be called by the developer when accessing a resource that will not be loaded in a View.

The load() method only triggers the loading of the resource the first time it is called. The subsequent calls return the same promise.

It's possible to provide a signal to stop being interested into a Loadable instance load status. When the signal is aborted, the instance does not stop its loading process, only cancelLoad can abort it.

Parameter:
signal AbortSignal
optional

Signal object that can be used to abort the asynchronous task. The returned promise will be rejected with an Error named AbortError when an abort is signaled. See also AbortController for more information on how to construct a controller that can be used to deliver abort signals.

Returns:
Type Description
Promise Resolves when the resources have loaded.
on(type, listener){Object}

Registers an event handler on the instance. Call this method to hook an event with a listener.

Parameters:

A event type, or an array of event types, to listen for.

listener Function

The function to call when the event is fired.

Returns:
Type Description
Object Returns an event handler with a remove() method that can be called to stop listening for the event(s).
Property Type Description
remove Function When called, removes the listener from the event.
Example:
view.on("click", function(event){
  // event is the event handle returned after the event fires.
  console.log(event.mapPoint);
});
when(callback, errback){Promise}
Since: ArcGIS API for JavaScript 4.6

when() may be leveraged once an instance of the class is created. This method takes two input parameters: a callback function and an errback function. The callback executes when the instance of the class loads. The errback executes if the instance of the class fails to load.

Parameters:
callback Function
optional

The function to call when the promise resolves.

errback Function
optional

The function to execute when the promise fails.

Returns:
Type Description
Promise Returns a new promise for the result of callback that may be used to chain additional functions.
Example:
// Although this example uses MapView, any class instance that is a promise may use when() in the same way
let view = new MapView();
view.when(function(){
  // This function will execute once the promise is resolved
}, function(error){
  // This function will execute if the promise is rejected due to an error
});

Event Overview

Name Type Summary Class
{view: View,layerView: LayerView}

Fires after the layer's LayerView is created and rendered in a view.

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{view: View,error: Error}

Fires when an error emits during the creation of a LayerView after a layer has been added to the map.

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{view: View,layerView: LayerView}

Fires after the layer's LayerView is destroyed and no longer renders in a view.

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Event Details

layerview-create

Fires after the layer's LayerView is created and rendered in a view.

Properties:
view View

The view in which the layerView was created.

layerView LayerView

The LayerView rendered in the view representing the layer in layer.

See also:
Example:
// This function will fire each time a layer view is created for this
// particular view.
layer.on("layerview-create", function(event){
  // The LayerView for the layer that emitted this event
  event.layerView;
});
layerview-create-error

Fires when an error emits during the creation of a LayerView after a layer has been added to the map.

Properties:
view View

The view that failed to create a layerview for the layer emitting this event.

error Error

An error object describing why the layer view failed to create.

See also:
Example:
// This function fires when an error occurs during the creation of the layer's layerview
layer.on("layerview-create-error", function(event) {
  console.error("LayerView failed to create for layer with the id: ", layer.id, " in this view: ", event.view);
});
layerview-destroy

Fires after the layer's LayerView is destroyed and no longer renders in a view.

Properties:
view View

The view in which the layerView was destroyed.

layerView LayerView

The destroyed LayerView representing the layer.