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 quering, visualizing, analyzing data

Layer typeData sourceData typesFeaturesLimitations
FeatureLayerArcGIS FeatureServer/MapServer, ArcGIS Portal item, or client-side graphicsPoints, polylines, polygons downloaded as vector graphicsClient-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
GraphicsLayerClient-side graphicsPoints, polylines, polygons displayed as vector graphicsNo 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.
MapImageLayerArcGIS MapServer,
ArcGIS Portal item
Points, polylines, polygons, rasters exported in a single imageMay 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 workspacesNo editing support
SceneLayerArcGIS SceneServer, ArcGIS Portal itemPoint and multipatch geometriesCan display a large number of features on the client. Ideal for rendering 3D featuresNo 2D support; no editing
CSVLayerCSV filePoints downloaded as vector graphicsClient-side processing, popup templates, renderers with 2D and 3D symbolsMay require large download depending on the number of features
StreamLayerArcGIS StreamServerPoints downloaded as vector graphicsDownloads and updates feature locations in real timen/a
ImageryLayerArcGIS ImageServer, ArcGIS Portal itemRaster data exported as a single imageClient-side and server-side pixel filtering and rendering; popup templates; queryingn/a
GeoRSSLayerGeoRSS feedPoints, polylines, polygonsNo geometry schema; popup templatesNo 3D support; no support for renderers
MapNotesLayerArcGIS Portal itemPoints, polylines, polygons, textMap Notes in a webmapNo 3D support; read-only
WMSLayerWMS service,
ArcGIS Portal item
Data exported as a single imageOGC specificationNo 3D support

Layers for providing geographic context

Layer typeData sourceData typesFeaturesLimitations
TileLayerArcGIS MapServer, ArcGIS Portal itemImage tilesBetter performance for large datasets; querying featuresNo editing, client-side rendering, or popup templates; some schema limitations in 3D views.
VectorTileLayerArcGIS Portal itemPoints, polylines, and polygons rendered as vector tilesFeatures may be styled client-side and used as a tiled basemapNo editing, client-side rendering, or popup templates.
IntegratedMeshLayerArcGIS SceneServer, ArcGIS Portal itemPoint cloud mesh integrated with imageryDisplays 3D objects with a high level of detailNo 2D support
ElevationLayerArcGIS ImageServer, ArcGIS Portal itemTiled elevation mesh/surfaceRenders elevation surfaces in 3D viewsNo 2D support
PointCloudLayerArcGIS SceneServer, ArcGIS Portal itemPoint clouds (e.g. collected from LiDAR)Renderers; fast display of point cloudsNo 2D support
OpenStreetMapLayerOpenStreetMap tile servicesImage tilesDisplays OpenStreetMap tiled contentn/a
WMTSLayerWMTS tile services,
ArcGIS Portal item
Image tilesOGC specificationNo 3D support
WebTileLayernon-ArcGIS, non-OGC, and non-OSM tile servicesImage tilesn/aNo editing, client-side rendering, or popup templates.

Other layers

Layer typeData sourceData typesFeaturesLimitations
GroupLayerAny combination of other layer typesn/aCombines two or more layers into a single layern/a

An instance of any layer is also a Promise. This allows you to execute code once the promise resolves, or when the layer finishes loading its resources. See then() for additional details.

See also:

Property Overview

Any properties can be set, retrieved or listened to. See the Working with Properties topic.
NameTypeSummaryClass
String

The name of the class.

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more detailsAccessor
Extent

The full extent of the layer.

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more detailsLayer
String

The unique ID assigned to the layer.

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more detailsLayer
String

Indicates how the layer should display in the LayerList widget.

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more detailsLayer
Boolean

Indicates whether the layer's resources have loaded.

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more detailsLayer
Error

The Error object returned if an error occurred while loading.

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more detailsLayer
String

Represents the status of a load operation.

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more detailsLayer
Object[]

A list of warnings which occurred while loading.

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more detailsLayer
Number

The opacity of the layer.

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more detailsLayer
String

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

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more detailsLayer
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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more detailsLayer

Property Details

declaredClassStringreadonly inherited

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

fullExtentExtent autocast

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.then(function(){
  view.extent = layer.fullExtent;
});

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

listModeString

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

ValueDescription
showThe layer is visible in the table of contents.
hideThe layer is hidden in the table of contents.
hide-childrenIf the layer is a GroupLayer, hide the children layers from the table of contents.
Default Value: show

loadedBooleanreadonly

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

Default Value: false

loadErrorErrorreadonly

The Error object returned if an error occurred while loading.

Default Value: null

loadStatusStringreadonly

Represents the status of a load operation.

ValueDescription
not-loadedThe object's resources have not loaded.
loadingThe object's resources are currently loading.
loadedThe object's resources have loaded without errors.
failedThe object's resources failed to load. See loadError for more details.
Default Value: not-loaded

loadWarningsObject[]readonly

A list of warnings which occurred while loading.

opacityNumber

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;

titleString

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

typeStringreadonly

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 | elevation | feature | graphics | group | imagery | integrated-mesh | map-image | open-street-map | point-cloud | scene | stream | tile | unknown | unsupported | vector-tile | web-tile

visibleBoolean

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

NameReturn TypeSummaryClass
Promise

An instance of this class is a Promise.

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more detailsLayer

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

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more detailsLayer

Emits an event on the instance.

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more detailsLayer
Promise<Object>

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

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more detailsLayer
Promise<Layer>

Creates a new layer instance from an ArcGIS Server URL.

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more detailsLayer
Promise<Layer>

Creates a new layer instance of the appropriate layer class from an ArcGIS Online or ArcGIS for Portal 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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more detailsLayer
Boolean

An instance of this class is a Promise.

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more detailsLayer
Boolean

An instance of this class is a Promise.

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more detailsLayer
Boolean

An instance of this class is a Promise.

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more detailsLayer
Promise

Loads the resources referenced by this class.

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more detailsLayer
Object

Registers an event handler on the instance.

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more detailsLayer
Promise

An instance of this class is a Promise.

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more detailsLayer
Promise

An instance of this class is a Promise.

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more detailsLayer

Method Details

always(callbackOrErrback){Promise}

An instance of this class is a Promise. Therefore always() may be used to execute a function if the promise is rejected or resolved. The input function will always execute no matter the response. For more information about promises, see the Working with Promises guide page.

Parameter:
callbackOrErrback Function
optional

The function to execute when the promise is rejected or resolved.

Returns:
TypeDescription
PromiseReturns a new promise for the result of callbackOrErrback.
Example:
// Although this example uses MapView, any class instance that is a promise may use always() in the same way
var view = new MapView();
view.always(function(){
  // This function will always execute whether or not the promise is resolved or rejected
});

cancelLoad()

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

emit(type, event)protected

Since: ArcGIS API for JavaScript 4.5

Emits an event on the instance. This method should only be used when creating subclasses that inherit from Evented.

Parameters:
type String

The name of the event.

event Object

The event payload.

fetchAttributionData(){Promise<Object>}

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

Returns:
TypeDescription
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, SceneLayer, StreamLayer, 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.

Parameters:
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:
TypeDescription
Promise< Layer>Returns a promise that resolves to the new Layer instance.
Example:
// get an ArcGIS server url from a custom function
var 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);
});

fromPortalItem(params){Promise<Layer>}static

Creates a new layer instance of the appropriate layer class from an ArcGIS Online or ArcGIS for Portal 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.

See also: isLayer

Parameters:
params Object

The parameters for loading the portal item.

Specification:
portalItem PortalItem

The object representing an ArcGIS Online or ArcGIS for Portal item from which to load the layer.

Returns:
TypeDescription
Promise< Layer>Returns a promise which resolves to the new layer instance.
Example:
Layer.fromPortalItem({
  portalItem: {  // autocasts new PortalItem()
    id: "8444e275037549c1acab02d2626daaee"
  }
}).then(function(layer){
  // add the layer to the map
  map.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:
TypeDescription
BooleanReturns true if the class supports the input event.

isFulfilled(){Boolean}

An instance of this class is a Promise. Therefore isFulfilled() may be used to verify if the promise is fulfilled (either resolved or rejected). If it is fulfilled, true will be returned. See the Working with Promises guide page for more information about promises.

Returns:
TypeDescription
BooleanIndicates whether the promise has been fulfilled (either resolved or rejected).

isRejected(){Boolean}

An instance of this class is a Promise. Therefore isRejected() may be used to verify if the promise is rejected. If it is rejected, true will be returned. See the Working with Promises guide page for more information about promises.

Returns:
TypeDescription
BooleanIndicates whether the promise has been rejected.

isResolved(){Boolean}

An instance of this class is a Promise. Therefore isResolved() may be used to verify if the promise is resolved. If it is resolved, true will be returned. See the Working with Promises guide page for more information about promises.

Returns:
TypeDescription
BooleanIndicates whether the promise has been resolved.

load(){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.

Returns:
TypeDescription
PromiseResolves 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. See the Events summary table for a list of listened events.

Parameters:
type String

The name of event to listen for.

listener Function

The function to call when the event is fired.

Returns:
TypeDescription
ObjectReturns an event handler with a remove() method that can be called to stop listening for the event.
PropertyTypeDescription
removeFunctionWhen called, removes the listener from the event.
See also:
Example:
view.on("click", function(event){
  // event is the event handle returned after the event fires.
  console.log(event.mapPoint);
});

otherwise(errback){Promise}

An instance of this class is a Promise. Use otherwise() to call a function once the promise is rejected.

Parameter:
errback Function
optional

The function to execute when the promise fails.

Returns:
TypeDescription
PromiseReturns a new promise for the result of errback.
Example:
// Although this example uses MapView, any class instance that is a promise may use otherwise() in the same way
var view = new MapView();
view.otherwise(function(error){
  // This function will execute if the promise is rejected due to an error
});

then(callback, errback, progback){Promise}

An instance of this class is a Promise. Therefore then() 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 promise resolves (when the instance of the class loads). The errback executes if the promise fails. See the Working with Promises guide page for additional details.

Parameters:
callback Function
optional

The function to call when the promise resolves.

errback Function
optional

The function to execute when the promise fails.

progback Function
optional

The function to invoke when the promise emits a progress update.

Returns:
TypeDescription
PromiseReturns 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 then() in the same way
var view = new MapView();
view.then(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

NameTypeSummaryClass
{view: View,layerView: LayerView}

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

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more detailsLayer
{view: View,layerView: LayerView}

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

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more detailsLayer

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-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.

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