// Construct Stream Layer
streamLayer = new StreamLayer({
  url: "https://geoeventsample1.esri.com:6443/arcgis/rest/services/LABus/StreamServer",
  purgeOptions: {
    displayCount: 10000
  },
  maxReconnectionAttempts: 100,
  maxReconnectionInterval: 10,
  renderer: renderer
}
map.add(streamLayer);

const layer = new StreamLayer({
  popupTemplate: {
    content: "OBJECTID={OBJECTID}, TRACKID={TRACKID}",
  },
  webSocketUrl: "ws://localhost:8000",
  fields: [
    {
      name: "OBJECTID",
      alias: "ObjectId",
      type: "oid",
    },
    {
      name: "TRACKID",
      alias: "TrackId",
      type: "oid",
    }
  ],
  timeInfo: {
    trackIdField: "TRACKID"
  },
  geometryType: "point"
  maxReconnectionAttempts: 100,
  maxReconnectionInterval: 10,
  renderer: renderer
});
map.add(layer);

Property Overview

Property Details

blendMode String

Since: ArcGIS API for JavaScript 4.16

Blend modes are used to blend layers together to create an interesting effect in a layer, or even to produce what seems like a new layer. Unlike the method of using transparency which can result in a washed-out top layer, blend modes can create a variety of very vibrant and intriguing results by blending a layer with the layer(s) below it.

When blending layers, a top layer is a layer that has a blend mode applied. All layers underneath the top layer are background layers. The default blending mode is normal where the top layer is simply displayed over the background layer. While this default behavior is perfectly acceptable, the use of blend modes on layers open up a world of endless possibilities to generate creative maps.

The layers in a GroupLayer are blended together in isolation from the rest of the map.

In the following screenshots, the vintage shaded relief layer is displayed over a firefly world imagery layer. The color blend mode is applied to the vintage shaded relief and the result looks a new layer.

Known Limitations

• The blendMode is not supported in 3D SceneViews.
• The blendMode is not supported in printing and in legend.

The following factors will affect the blend result:

• Order of all layers
• Layer opacity
• Opacity of features in layers
• Visibility of layers
• By default, the very bottom layer in a map is drawn on a transparent background. You can change the MapView's background color.

Read more

Blend mode	Description
normal	The top layer is displayed over the background layer. The data of the top layer block the data of background layer where they overlap.
average	Takes the mathematical average of top and background layers. Result of average blend mode is often similar to the effect of setting the layer's opacity to 50%.

Lighten blend modes:

The following blend modes create lighter results than all layers. In lighten blend modes, pure black colors in the top layer become transparent allowing the background layer to show through. White in the top layer will stay unchanged. Any color that is lighter than pure black is going to lighten colors in the top layer to varying degrees all way to pure white.

Lighten blend modes can be useful when lightening dark colors of the top layer or removing black colors from the result. The plus, lighten and screen modes can be used to brighten layers that have faded or dark colors on a dark background.

Blend mode	Description
lighten	Compares top and background layers and retains the lighter color in the top layer. Colors in the top layer become transparent if they are darker than the overlapping colors in the background layer allowing the background layer to show through completely. Can be thought of as the opposite of darken blend mode.
lighter	Colors in top and background layers are multiplied by their alphas (layer opacity and layer's data opacity. Then the resulting colors are added together. All overlapping midrange colors are lightened in the top layer. The opacity of layer and layer's data will affect the blend result.
plus	Colors in top and background layers are added together. All overlapping midrange colors are lightened in the top layer. This mode is also known as add or linear-dodge.
screen	Inverts colors of the background layer and multiplies with colors of the top layer. The resulting colors will be lighter than the original color with less contrast. Screen can produce many different levels of brightening depending on the luminosity values of the top layer. Can be thought of as the opposite of the multiply mode.
color-dodge	Creates a brighter effect by decreasing the contrast between the top and background layers, resulting in saturated mid-tones and bright highlights.

Darken blend modes:

The following blend modes create darker results than all layers. In darken blend modes, pure white in the top layer will become transparent allowing the background layer to show through. Black in the top layer will stay unchanged. Any color that is darker than pure white is going to darken a top layer to varying degrees all the way to pure black.

The multiply blend mode is often used to highlight shadows, show contrast, or accentuate an aspect of a map. For example, you can use multiply blend mode on a topographic map displayed over hillshade when you want to have your elevation show through the topographic layer. See the intro to layer blending sample.

The multiply and darken modes can be used to have dark labels of the basemap to show through top layers. See the darken blending sample.

The color-burn mode works well with colorful top and background layers since it increases saturation in mid-tones. It increases the contrast by tinting pixels in overlapping areas in top and bottom layers more towards the top layer color. Use this blend mode, when you want an effect with more contrast than multiply or darken.

The following screenshots show how the multiply blend mode used for creating a physical map of the world that shows both boundaries and elevation.

Blend mode	Description
darken	Emphasizes the darkest parts of overlapping layers. Colors in the top layer become transparent if they are lighter than the overlapping colors in the background layer, allowing the background layer to show through completely.
multiply	Emphasizes the darkest parts of overlapping layers by multiplying colors of the top layer and the background layer. Midrange colors from top and background layers are mixed together more evenly.
color-burn	Intensifies the dark areas in all layers. It increases the contrast between top and background layers, by tinting colors in overlapping area towards the top color. To do this it inverts colors of the background layer, divides the result by colors of the top layer, then inverts the results.

Contrast blend modes:

The following blend modes create contrast by both lightening the lighter areas and darkening the darker areas in the top layer by using lightening or darkening blend modes to create the blend. The contrast blend modes will lighten the colors lighter than 50% gray ([128,128,128]), and darken the colors darker than 50% gray. 50% gray will be transparent in the top layer. Each mode can create a variety of results depending on the colors of top and background layers being blended together. The overlay blend mode makes its calculations based on the brightness of the colors in the background layer while all of the other contrast blend modes make their calculations based on the brightness of the top layer. Some of these modes are designed to simulate the effect of shining a light through the top layer, effectively projecting upon the layers beneath it.

Contrast blend modes can be used to increase the contrast and saturation to have more vibrant colors and give a punch to your layers. For example, you can duplicate a layer and set overlay blend mode on the top layer to increase the contrast and tones of your layer. You can also add a polygon layer with a white fill symbol over a dark imagery layer and apply soft-light blend mode to increase the brightness in the imagery layer.

The following screenshots show an effect of the overlay blend mode on a GraphicsLayer. The left image shows when the buffer graphics layer has the normal blend mode. As you can see, the gray color for the buffer polygon is blocking the intersecting census tracts. The right image shows when the overlay blend mode is applied to the buffer graphics layer. The overlay blend mode darkens or lightens the gray buffer polygon depending on the colors of the background layer while the census tracts layer is shining through. See this in action.

Normal blend mode	Overlay blend mode

Blend mode	Description
overlay	Uses a combination of multiply and screen modes to darken and lighten colors in the top layer with the background layer always shining through. The result is darker color values in the background layer intensify the top layer, while lighter colors in the background layer wash out overlapping areas in the top layer.
soft-light	Applies a half strength screen mode to lighter areas and and half strength multiply mode to darken areas of the top layer. You can think of the soft-light as a softer version of the overlay mode.
hard-light	Multiplies or screens the colors, depending on colors of the top layer. The effect is similar to shining a harsh spotlight on the top layer.
vivid-light	Uses a combination of color-burn or color-dodge by increasing or decreasing the contrast, depending on colors in the top layer.

Component blend modes:

The following blend modes use primary color components, which are hue, saturation and luminosity to blend top and background layers. You can add a feature layer with a simple renderer over any layer and set hue, saturation, color or luminosity blend mode on this layer. With this technique, you create a brand new looking map.

The following screenshots show where the topo layer is blended with world hillshade layer with luminosity blend mode. The result is a drastically different looking map which preserves the brightness of the topo layer while adapting the hue and saturation of the hillshade layer.

Blend mode	Description
hue	Creates an effect with the hue of the top layer and the luminosity and saturation of the background layer.
saturation	Creates an effect with the saturation of the top layer and the hue and luminosity of the background layer. 50% gray with no saturation in the background layer will not produce any change.
luminosity	Creates effect with the luminosity of the top layer and the hue and saturation of the background layer. Can be thought of as the opposite of color blend mode.
color	Creates an effect with the hue and saturation of the top layer and the luminosity of the background layer. Can be thought of as the opposite of luminosity blend mode.

Composite blend modes:

The following blend modes can be used to mask the contents of top, background or both layers.

• Destination modes are used to mask the data of the top layer with the data of the background layer.
• Source modes are used to mask the data of the background layer with the data of the top layer.

The destination-in blend mode can be used to show areas of focus such as earthquakes, animal migration, or point-source pollution by revealing the underlying map, providing a bird’s eye view of the phenomenon. Check out multiple blending and groupLayer blending samples to see composite blend modes in action.

The following screenshots show feature and imagery layers on the left side on their own in the order they are drawn in the view. The imagery layer that contains land cover classification rasters. The feature layer contains 2007 county crops data. The right image shows the result of layer blending where destination-in blendMode is set on the imagery layer. As you can see, the effect is very different from the original layers. The blended result shows areas of cultivated crops only (where both imagery and feature layers overlap).

Blend mode	Description
destination-over	Destination/background layer covers the top layer. The top layer is drawn underneath the destination layer. You'll see the top layer peek through wherever the background layer is transparent or has no data.
destination-atop	Destination/background layer is drawn only where it overlaps the top layer. The top layer is drawn underneath the background layer. You'll see the top layer peek through wherever the background layer is transparent or has no data.
destination-in	Destination/background layer is drawn only where it overlaps with the top layer. Everything else is made transparent.
destination-out	Destination/background layer is drawn where it doesn't overlap the top layer. Everything else is made transparent.
source-atop	Source/top layer is drawn only where it overlaps the background layer. You will see the background layer peek through where the source layer is transparent or has no data.
source-in	Source/top layer is drawn only where it overlaps with the background layer. Everything else is made transparent.
source-out	Source/top layer is drawn where it doesn't overlap the background layer. Everything else is made transparent.
xor	Top and background layers are made transparent where they overlap. Both layers are drawn normal everywhere else.

Invert blend modes:

The following blend modes either invert or cancel out colors depending on colors of the background layer. These blend modes look for variations between top and background layers. For example, you can use difference or exclusion blend modes on two imagery layers of forest covers to visualize how forest covers changed from one year to another.

The invert blend mode can be used to turn any light basemap into a dark basemap to accommodate those who work in low-light conditions. The following screenshots show how setting the invert blend mode set on a feature layer with a simple renderer turns the world terrain basemap into a dark themed basemap in no time.

Blend mode	Description
difference	Subtracts the darker of the overlapping colors from the lighter color. When two pixels with the same value are subtracted, the result is black. Blending with black produces no change. Blending with white inverts the colors. This blending mode is useful for aligning layers with similar content.
exclusion	Similar to the difference blend mode, except that the resulting image is lighter overall. Overlapping areas with lighter color values are lightened, while darker overlapping color values become transparent.
minus	Subtracts colors of the top layer from colors of the background layer making the blend result darker. In the case of negative values, black is displayed.
invert	Inverts the background colors wherever the top and background layers overlap. The invert blend mode inverts the layer similar to a photographic negative.
reflect	This blend mode creates effects as if you added shiny objects or areas of light in the layer. Black pixels in the background layer are ignored as if they were transparent.

Possible Values:"average"|"color-burn"|"color-dodge"|"color"|"darken"|"destination-atop"|"destination-in"|"destination-out"|"destination-over"|"difference"|"exclusion"|"hard-light"|"hue"|"invert"|"lighten"|"lighter"|"luminosity"|"minus"|"multiply"|"normal"|"overlay"|"plus"|"reflect"|"saturation"|"screen"|"soft-light"|"source-atop"|"source-in"|"source-out"|"vivid-light"|"xor"

Default Value:normal

See also:

• Layer blending samples

copyright String

Since: ArcGIS API for JavaScript 4.15

Copyright information for the layer.

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.

definitionExpression String

The SQL where clause used to filter features based on their attributes. Only the features that satisfy the definition expression are displayed in the View. Setting a definition expression is useful when the dataset is large and you don't want to bring all features to the client for analysis. Definition expressions may be set when a layer is constructed prior to it loading in the view or after it has been added to the map. If the definition expression is set after the layer has been added to the map, the view will automatically refresh itself to display the features that satisfy the new definition expression.

Examples:

// Set a definition expression in a constructor to only display features that
// "region = 'central'". Also only keep the latest 10 features per track id.
const streamLayer = new StreamLayer({
  url: svcUrl,
  definitionExpression: "region = 'central'",
  purgeOptions: {
    displayCount: 10000,
    maxObservations: 10
  }
});

// Set the definition expression directly on layer instance to
// only display buses going on route 70.
streamLayer.definitionExpression = "route_id = '70'";

displayField String

Since: ArcGIS API for JavaScript 4.15

The name of the layer's primary display field. The value of this property matches the name of one of the fields of the layer.

effect Effect

Since: ArcGIS API for JavaScript 4.18

Effect provides various filter functions that can be performed on the layer to achieve different visual effects similar to how image filters work. This powerful capability allows you to apply css filter-like functions to layers to create custom visual effects to enhance the cartographic quality of your maps. This is done by applying the desired effect to the layer's effect property as a string or an array of objects to set scale dependent effects.

Known Limitations

• The effect is not supported in 3D SceneViews.
• The effect is not supported in printing and in legend.

Default Value:null

See also:

• More information on how to set effect

• Layer and layer view effect samples

Examples:

// the following effect will be applied to the layer at all scales
// brightness will be applied first, then hue-rotate followed by contrast
// changing order of the effects will change the final result
layer.effect = "brightness(5) hue-rotate(270deg) contrast(200%)";

// set a scale dependent bloom effect on the layer
layer.effect = [
  {
    scale: 36978595,
    value: "drop-shadow(3px, 3px, 4px)"
  },
  {
    scale: 18489297,
    value: "drop-shadow(2px, 2px, 3px)"
  },
  {
    scale: 4622324,
    value: "drop-shadow(1px, 1px, 2px)"
  }
];

elevationInfo Object

Specifies how graphics are placed on the vertical axis (z). This property may only be used in a SceneView. See the ElevationInfo sample for an example of how this property may be used.

Properties:

mode String Defines how the feature is placed with respect to the terrain surface or 3D objects in the scene. If the geometry consists of multiple points (e.g. lines or polygons), the elevation is evaluated separately for each point. See the table below for a list of possible values. Mode Description on-the-ground Features are aligned to the Ground. If the scene contains an IntegratedMeshLayer, then features are aligned to the IntegratedMeshLayer. If features have z-values, then the z-values are ignored in this mode. Features with 2D symbols are draped on the Ground or IntegratedMeshLayer. This is the default mode for layers without z-values containing Polyline, Polygon features or Point features rendered with ObjectSymbol3DLayer. absolute-height Features are placed at an absolute elevation (z-value) above sea level. This z-value is determined by the geometry's z-value (if present). If featureExpressionInfo is defined, the result of the expression is used instead of the geometry’s z-value. This mode doesn't take the elevation of the Ground or any other layers into account. This is the default value of features with any geometry type where hasZ is true. relative-to-ground Features are placed at an elevation relative to the Ground or IntegratedMeshLayer. The feature's elevation is determined by summing up the elevation of the Ground or IntegratedMeshLayer and the geometry's z-value (if present). If featureExpressionInfo is defined, the result of the expression is used instead of the geometry’s z-value. If the geometries don't have z-values, relative-to-ground is the default value for Point geometries rendered with IconSymbol3DLayers. relative-to-scene Features are aligned to extruded polygons, 3D Object SceneLayers or BuildingSceneLayers, depending on which one has higher elevation. If the feature is not directly above a building or any other feature, it is aligned to the elevation of the Ground or the IntegratedMeshLayer. If defined, the result of featureExpressionInfo is added to the elevation. In this mode z-values are ignored. Possible Values:"on-the-ground"|"relative-to-ground"|"absolute-height"|"relative-to-scene"

offset Number optional An elevation offset, which is added to the vertical position of the graphic. If unit is not defined, the offset is in meters. When mode = "on-the-ground", this property has no effect.

featureExpressionInfo Object optional This object contains information about setting a custom z-value on the feature. Specification: expression String optional An Arcade expression evaluating to a number that determines the z-value of the feature. When mode = "on-the-ground", this property has no effect. For line and polygon geometries the result of the expression is the same for all vertices of a feature.

unit String optional The unit for featureExpressionInfo and offset values. Possible Values:"feet"|"meters"|"kilometers"|"miles"|"us-feet"|"yards"

featureReduction FeatureReductionSelectionautocast

Since: ArcGIS API for JavaScript 4.4

Configures the method for reducing the number of point features in the view. By default this property is null, which indicates the layer view should draw every feature.

StreamLayer supports one type feature reduction: selection. Selection only applies to points in a SceneView and involves thinning overlapping features so no features intersect on screen.

See also:

• Sample: Point styles for cities

Example:

// thins features in the view
layer.featureReduction = {
  type: "selection"
};

fields Field[]autocast

Autocasts from Object[]

Since: ArcGIS API for JavaScript 4.15

An array of fields in the layer.

Example:

// define each field's schema
var fields = [
 new Field({
   "name": "ObjectID",
   "alias": "ObjectID",
   "type": "oid"
 }), new Field({
   "name": "description",
   "alias": "Description",
   "type": "string"
 }), new Field ({
   "name": "title",
   "alias": "Title",
   "type": "string"
 })
];

fieldsIndex FieldsIndexreadonly

Since: ArcGIS API for JavaScript 4.12

A convenient property that can be used to make case-insensitive lookups for a field by name. It can also provide a list of the date fields in a layer.

Example:

// lookup a field by name. name is case-insensitive
const field = layer.fieldsIndex.get("SoMeFiEld");

if (field) {
  console.log(field.name); // SomeField
}

geometryDefinition Extentautocast

An extent object used to filter features. Only features that intersect the extent object are displayed in the view. For example, the geometryDefinition can be set to a city boundary extent to display features only intersect this extent.

Example:

// Get the current extent of the map view and expand the extent by factor of 0.9
// Then apply this extent to stream layer's geometryDefinition.
// Only features that intersect this extent will be displayed on the view.
var extent = mapView.extent.clone().expand(0.9);
streamLayer.geometryDefinition = extent;

geometryType String

The geometry type of features in the layer. All features must be of the same type.

Possible Values:"point"|"polygon"|"polyline"|"multipoint"

id String inherited

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

labelingInfo LabelClass[]autocast

Autocasts from Object[]

The label definition for this layer, specified as an array of LabelClass. Use this property to specify labeling properties for the layer such as label expression, placement, and size.

Multiple Label classes with different where clauses can be used to define several labels with varying styles on the same feature. Likewise, multiple label classes may be used to label different types of features (for example blue labels for boats and green labels for trucks).

Known Limitations

• Currently only one LabelClass is supported in 3D SceneViews.

See also:

• Sample: Flat vs. volumetric 3D symbol layers

• Sample: Add multiple label classes to a layer

• Sample: Multi-line labels

Example:

const boatLabelClass = new LabelClass({
  labelExpressionInfo: { expression: "$feature.NAME" },
  symbol: {
    type: "label-3d",  // autocasts as new LabelSymbol3D()
    symbolLayers: [{
      type: "text",  // autocasts as new TextSymbol3DLayer()
      material: { color: [ 49,163,84 ] },
      size: 12  // points
    }]
  }
});

streamLayer.labelingInfo = [ boatLabelClass ];

labelsVisible Boolean

Indicates whether to display labels for this layer. If true, labels will appear as defined in the labelingInfo property.

Default Value:true

legendEnabled Boolean

Indicates whether the layer will be included in the legend.

Default Value:true

listMode String inherited

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 inherited

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

Default Value:false

loadError Errorreadonly inherited

The Error object returned if an error occurred while loading.

Default Value:null

loadStatus Stringreadonly inherited

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 inherited

A list of warnings which occurred while loading.

maxReconnectionAttempts Number

Since: ArcGIS API for JavaScript 4.17

The maximum number of attempts to reconnect. If 0, the client will always continue to try to reconnect. Cannot be changed after the layer has been loaded.

maxReconnectionInterval Number

Since: ArcGIS API for JavaScript 4.17

The maximum time to wait in seconds between attempts to reconnect. Cannot be changed after the layer has been loaded.

maxScale Number

The maximum scale (most zoomed in) at which the layer is visible in the view. If the map is zoomed in beyond this scale, the layer will not be visible. A value of 0 means the layer does not have a maximum scale. The maxScale value should always be smaller than the minScale value, and greater than or equal to the service specification.

Default Value:0

Examples:

// The layer will not be visible when the view is zoomed in beyond a scale of 1:1,000
layer.maxScale = 1000;

// The layer's visibility is not restricted to a maximum scale.
layer.maxScale = 0;

minScale Number

The minimum scale (most zoomed out) at which the layer is visible in the view. If the map is zoomed out beyond this scale, the layer will not be visible. A value of 0 means the layer does not have a minimum scale. The minScale value should always be larger than the maxScale value, and lesser than or equal to the service specification.

Default Value:0

Examples:

// The layer will not be visible when the view is zoomed out beyond a scale of 1:3,000,000
layer.minScale = 3000000;

// The layer's visibility is not restricted to a minimum scale.
layer.minScale = 0;

objectIdField String

The name of an oid field containing a unique value or identifier for each feature in the layer.

See also:

• fields

opacity Number inherited

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;

popupEnabled Boolean

Indicates whether to display popups when features in the layer are clicked. The layer needs to have a popupTemplate to define what information should be displayed in the popup. Alternatively, a default popup template may be automatically used if Popup.defaultPopupTemplateEnabled is set to true.

Default Value:true

See also:

• createPopupTemplate

• View

popupTemplate PopupTemplateautocast

The popup template for the layer. When set on the layer, the popupTemplate allows users to access attributes and display their values in the view's popup when a feature is selected using text and/or charts. See the PopupTemplate sample for an example of how PopupTemplate interacts with a FeatureLayer.

A default popup template is automatically used if no popupTemplate has been defined when Popup.defaultPopupTemplateEnabled is set to true.

See also:

• createPopupTemplate

• View

purgeOptions Object

Options for purging stale features. The purge options controls how much data is removed from StreamLayerView and how often. Choosing the right purge rule for your stream layer is critical for maximizing functionality and performance. Cannot be changed after the layer has been loaded.

Properties:

age Number optional Specifies the maximum age of a feature in minutes. It purges features whose start time specified in the startField of the feature is older than the age. If no new features coming in then the age of the application does not advance.

ageReceived Number optional Specifies the maximum age of a feature in minutes since it arrived in the application. The features older than specified ageReceived will be removed.

displayCount Number optional Controls the overall maximum number of features.

maxObservations Number optional Controls the maximum number of observations to show within a track. If trackIdField is not configured on the geoevent service, this property will have no effect. The default is 1.

renderer Rendererautocast

The renderer assigned to the layer. The renderer defines how to visualize each feature in the layer. Depending on the renderer type, features may be visualized with the same symbol, or with varying symbols based on the values of provided attribute fields or functions. If not specified, a default renderer will be generated based on the geometry type.

See also:

• Manually defined renderers

screenSizePerspectiveEnabled Boolean

Since: ArcGIS API for JavaScript 4.4

Apply perspective scaling to screen-size point symbols in a SceneView. When true, screen sized objects such as icons, labels or callouts integrate better in the 3D scene by applying a certain perspective projection to the sizing of features. This only applies when using a SceneView.

layer.screenSizePerspectiveEnabled = true

layer.screenSizePerspectiveEnabled = false

Known Limitations

Screen size perspective is currently not optimized for situations where the camera is very near the ground, or for scenes with point features located far from the ground surface. In these cases it may be better to turn off screen size perspective. As screen size perspective changes the size based on distance to the camera, it should be set to false when using size visual variables.

Default Value:true

See also:

• Sample: Point styles for cities

sourceJSON Object

Since: ArcGIS API for JavaScript 4.13

The stream service's metadata JSON exposed by the ArcGIS REST API. While most commonly used properties are exposed on the StreamLayer class directly, this property gives access to all information returned by the stream service. This property is useful if working in an application built using an older version of the API which requires access to stream service properties from a more recent version.

spatialReference SpatialReferenceautocast

The spatial reference of the layer. When creating the layer from a url, the spatial reference is read from the service.

When creating a StreamLayer from client-side features, this property is inferred from the geometries of the features provided in the source property.

timeExtent TimeExtentautocast

Since: ArcGIS API for JavaScript 4.14

The layer's time extent. When the layer's useViewTime is false, the layer instructs the view to show data from the layer based on this time extent. If the useViewTime is true, and both layer and view time extents are set, then features that fall within the intersection of the view and layer time extents will be displayed. For example, if the layer's time extent is set to display features between 1970 and 1975 and the view has a time extent set to 1972-1980, the effective time on the feature layer will be 1972-1975.

Default Value:null

Examples:

if (!layer.useViewTime) {
  if (layer.timeExtent) {
    console.log("Current timeExtent:", layer.timeExtent.start, " - ", layer.timeExtent.end}
  } else {
    console.log("The layer will display data within the view's timeExtent.");
    console.log("Current view.timeExtent:", view.timeExtent.start, " - ", view.timeExtent.end}
  }
}

// set the timeExtent on the layer and useViewTime false
// In this case, the layer will honor its timeExtent and ignore
// the view's timeExtent
const layer = new ImageryLayer({
  url: "https://sampleserver6.arcgisonline.com/arcgis/rest/services/ScientificData/SeaTemperature/ImageServer",
  timeExtent: {
    start: new Date(2014, 4, 18),
    end: new Date(2014, 4, 19)
  },
  useViewTime: false
});

// timeExtent is set on the layer and the view
// In this case, the layer will display features that fall
// within the intersection of view and layer time extents
// features within Jan 1, 1976 - Jan 1, 1981 will be displayed
const view = new MapView({
  timeExtent: {
    start: new Date(1976, 0, 1),
    end: new Date(2002, 0, 1)
  }
});
const layer = new FeatureLayer({
  url: myUrl,
  timeExtent: {
    start: new Date(1974, 0, 1),
    end: new Date(1981, 0, 1)
  }
});

timeInfo TimeInfoautocast

Since: ArcGIS API for JavaScript 4.11

TimeInfo provides information such as date fields that store start and end time for each feature and the fullTimeExtent for the layer. The timeInfo property, along with its startField and endField properties, must be set at the time of layer initialization if it is being set for a CSVLayer, GeoJSONLayer or FeatureLayer initialized from client-side features. The fullTimeExtent for timeInfo is automatically calculated based on its startField and endField properties. The timeInfo parameters cannot be changed after the layer is loaded.

Default Value:null

Example:

// create geojson layer from usgs earthquakes geojson feed
const geojsonLayer = new GeoJSONLayer({
  url: "https://earthquake.usgs.gov/earthquakes/feed/v1.0/summary/all_month.geojson",
  copyright: "USGS Earthquakes",
  fields: [
    { "name": "mag", "type": "double" },
    { "name": "place", "type": "string" },
    { "name": "time", "type": "date" }, // date field
    { "name": "depth", "type": "double" }
  ],
  // timeInfo can be used to do temporal queries
  // set the startField and endField.
  // timeExtent is automatically calculated from the
  // the start and end date fields
  timeInfo: {
    startField: "time"
  }
});

timeOffset TimeIntervalautocast

Since: ArcGIS API for JavaScript 4.14

A temporary offset of the time data based on a certain TimeInterval. This allows users to overlay features from two or more time-aware layers with different time extents. For example, if a layer has data recorded for the year 1970, an offset value of 2 years would temporarily shift the data to 1972. You can then overlay this data with data recorded in 1972. A time offset can be used for display purposes only. The query and selection are not affected by the offset.

Default Value:null

Example:

// Offset a CSV Layer containing hurricanes from 2015 so that they appear in 2019 (+4 years).
var layer = new CSVLayer({
  url: `hurricanes-and-storms-2015.csv`,
  timeOffset: {
    value: 4,
    unit: "years"
  },
  timeInfo: {
    startField: "ISO_time"
  },
  renderer: {
    type: "simple",
    symbol: {
      type: "simple-marker",
      size: 6,
      color: "red",
      outline: {
        width: 0.5,
        color: "black"
      }
    }
  }
});

title String inherited

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

type Stringreadonly

For StreamLayer the type is stream.

For StreamLayer the type is always "stream".

updateInterval Number

Since: ArcGIS API for JavaScript 4.18

The minimum rate (ms) at which to poll for updates over the websocket connection. Increasing the updateInterval reduces the speed at which feature updates are applied.

Default Value:300

url String

The URL of the stream service. This is set in the url parameter of the constructor.

Example:

var layer = new StreamLayer({
 url: "https://geoeventsample3.esri.com:6443/arcgis/rest/services/SeattleBus/StreamServer"
});

useViewTime Boolean

Since: ArcGIS API for JavaScript 4.14

Determines if the layer will update its temporal data based on the view's timeExtent. When false, the layer will display its temporal data based on the layer's timeExtent, regardless of changes to the view. If both view and layer time extents are set while this property is true, then the features that fall within the intersection of the view and layer time extents will be displayed. For example, if a layer's time extent is set to display features between 1970 and 1975 and the view has a time extent set to 1972-1980, the effective time on the feature layer will be 1972-1975.

Default Value:true

Example:

if (featureLayer.useViewTime) {
  console.log("Displaying data between:", view.timeExtent.start, " - ", view.timeExtent.end);
}

visible Boolean inherited

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;

webSocketUrl String

Since: ArcGIS API for JavaScript 4.17

beta

The URL of a websocket connection. Can be used instead of url to specify a standalone WebSocket connection. See the section on StreamLayer from a custom stream service for more information.

See also:

• StreamLayer from a custom stream service

• Creating a custom stream service

Method Overview

Method Details

cancelLoad()inherited

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

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

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:

• Sample - Custom WebGL layer view

createPopupTemplate(options){PopupTemplate}

Since: ArcGIS API for JavaScript 4.11

Creates a popup template for the layer, populated with all the fields of the layer.

Parameter:

options CreatePopupTemplateOptions optional Options for creating the popup template.

Returns:

Type	Description
PopupTemplate	The popup template, or null if the layer does not have any fields.

destroy()inherited

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:

• Map.destroy()
• WebMap.destroy()
• WebScene.destroy()
• Basemap.destroy()
• Ground.destroy()
• PortalItem.destroy()

emit(type, event){Boolean}inherited

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

getField(fieldName){Field}

Since: ArcGIS API for JavaScript 4.15

Returns the Field instance for a field name (case-insensitive).

Parameter:

fieldName String Name of the field.

Returns:

Type	Description
Field	the matching field or undefined

See also:

• fields

getFieldDomain(fieldName, options){Domain}

Since: ArcGIS API for JavaScript 4.15

Returns the Domain associated with the given field name. The domain can be either a CodedValueDomain or RangeDomain.

Parameters:

fieldName String Name of the field.

options Object optional An object specifying additional options. See the object specification table below for the required properties of this object. Specification: feature Graphic The feature to which the Domain is assigned.

Returns:

Type	Description
Domain	The Domain object associated with the given field name for the given feature.

hasEventListener(type){Boolean}inherited

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}inherited

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}inherited

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}inherited

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}inherited

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}inherited

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

Parameters:

type String|String[] 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}inherited

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
var 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

{view: View,layerView: LayerView}

{view: View,error: Error}

{view: View,layerView: LayerView}

Event Details

layerview-createinherited

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:

• View.whenLayerView()

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-errorinherited

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:

• View.whenLayerView()

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-destroyinherited

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.