Legend | References | ArcGIS Maps SDK for JavaScript

import Legend from "@arcgis/core/widgets/Legend.js";

Inheritance:: Legend→Widget→Accessor

Since: ArcGIS Maps SDK for JavaScript 4.0

The Legend widget describes the symbols used to represent layers in a map. All symbols and text used in this widget are configured in the Renderer of the layer. The legend will only display layers and sublayers that are visible in the view unless respectLayerVisibility is false.

The legend automatically updates when

the visibility of a layer or sublayer changes
a layer is added or removed from the map
a layer's renderer, opacity, or title is changed
the legendEnabled property is changed (set to true or false on the layer)

You can use the view's DefaultUI to add widgets to the view's user interface via the ui property on the view.

Known Limitations

Currently, the legend widget does not support the following layer types: ElevationLayer, GraphicsLayer, IntegratedMeshLayer, KMLLayer, MapNotesLayer, OpenStreetMapLayer, VectorTileLayer, VideoLayer, and WebTileLayer. 3D symbols with more than one symbol layer are not supported. DictionaryRenderer is not supported.

Expand the "Read more" section below to view various examples of legends based on renderer type.

Continuous color

Classed color

Continuous size

Size - above and below

Dot density

Predominance

Relationship

See also

DefaultUI

Example

let legend = new Legend({
  view: view
});

view.ui.add(legend, "bottom-right");

Constructors

Constructor

Parameters

Parameter	Type	Description	Required
properties	`LegendProperties`

See the properties table for a list of all the properties that may be passed into the constructor.

Example

// typical usage
let legend = new Legend({
  view: view
});

Properties

Any properties can be set, retrieved or listened to. See the Watch for changes topic.

Property	Type	Class
`activeLayerInfos`	`Collection<ActiveLayerInfo>`
`basemapLegendVisible`	`boolean`
`container` inherited	`HTMLElement \| null \| undefined`	Widget
`declaredClass` readonly inherited	`string`	Accessor
`destroyed` readonly inherited	`boolean`	Widget
`headingLevel`	`HeadingLevel`
`hideLayersNotInCurrentView`	`boolean`
`icon`	`Icon["icon"]`
`id` inherited	`string`	Widget
`label`	`string`
`layerInfos`	`LayerInfo[]`
`respectLayerDefinitionExpression`	`boolean`
`respectLayerVisibility`	`boolean`
`style`	`LegendStyle`
`view`	`MapViewOrSceneView \| LinkChartView \| null \| undefined`
`viewModel`	`LegendViewModel`
`visible` inherited	`boolean`	Widget

activeLayerInfos

autocast Property

Type: Collection<ActiveLayerInfo>

Collection of ActiveLayerInfo objects used by the legend view to display data in the legend. The legend widget watches this property to hide or display the layer's legend when an ActiveLayerInfo is removed from or added to this collection.

basemapLegendVisible

Property

Type: boolean

Indicates whether to show the Basemap layers in the Legend. If you set this property to true and specify layerInfos, the basemap layers you want included in the legend must also be specified in layerInfos.

Default value: false

Example

legend.basemapLegendVisible = true;

container

autocast inherited Property

Type: HTMLElement | null | undefined

Inherited from: Widget

The ID or node representing the DOM element containing the widget. This property can only be set once. The following examples are all valid use case when working with widgets.

Examples

// Create the HTML div element programmatically at runtime and set to the widget's container
const basemapGallery = new BasemapGallery({
  view: view,
  container: document.createElement("div")
});

// Add the widget to the top-right corner of the view
view.ui.add(basemapGallery, {
  position: "top-right"
});

// Specify an already-defined HTML div element in the widget's container

const basemapGallery = new BasemapGallery({
  view: view,
  container: basemapGalleryDiv
});

// Add the widget to the top-right corner of the view
view.ui.add(basemapGallery, {
  position: "top-right"
});

// HTML markup
<body>
  <div id="viewDiv"></div>
  <div id="basemapGalleryDiv"></div>
</body>

// Specify the widget while adding to the view's UI
const basemapGallery = new BasemapGallery({
  view: view
});

// Add the widget to the top-right corner of the view
view.ui.add(basemapGallery, {
  position: "top-right"
});

declaredClass

readonlyinherited Property

Type: string

Inherited from: Accessor

Since: ArcGIS Maps SDK for JavaScript 4.7

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

destroyed

readonlyinherited Property

Type: boolean

Inherited from: Widget

When true, this property indicates whether the widget has been destroyed.

headingLevel

Property

Type: HeadingLevel

Since: ArcGIS Maps SDK for JavaScript 4.20

Indicates the heading level to use for the legend title. By default, legend titles are rendered as level 3 headings (e.g. <h3>Legend title</h3>). Depending on the legend placement in your app, you may need to adjust this heading for proper semantics. This is important for meeting accessibility standards.

See also

Heading Elements

Default value: 3

Example

// legend title will render as an <h2>
legend.headingLevel = 2;

hideLayersNotInCurrentView

Property

Type: boolean

Since: ArcGIS Maps SDK for JavaScript 4.21

When true, layers will only be shown in the legend if they are visible in the view's extent. When data from a layer is not visible in the view, the layer's legend information will be hidden. Only layers that implement the createQuery() and queryFeatureCount() methods are supported by hideLayersNotInCurrentView.

To hide layers completely from the legend, you should set the legendEnabled property of the layer to false.

See also

respectLayerVisibility

Default value: false

Example

// layers not displayed in the view
// will not be shown in the legend
legend.hideLayersNotInCurrentView = true;

icon

autocast Property

Type: Icon["icon"]

Since: ArcGIS Maps SDK for JavaScript 4.27

Icon which represents the widget. It is typically used when the widget is controlled by another one (e.g. in the Expand widget).

See also

Default value: "legend"

id

inherited Property

Type: string

Inherited from: Widget

The unique ID assigned to the widget when the widget is created. If not set by the developer, it will default to the container ID, or if that is not present then it will be automatically generated.

label

autocast Property

Type: string

Since: ArcGIS Maps SDK for JavaScript 4.7

The widget's default label.

layerInfos

Property

Type: LayerInfo[]

Defines which layers and sublayers are shown in the legend, including any basemap layers you want visible. If not set, all layers in the map are displayed in the legend by default, including basemap layers when basemapLegendVisible is true.

Example

const subtypeGroupLayer = webmap.layers.getItemAt(0);
const subtypeSubLayer = subtypeGroupLayer.sublayers.getItemAt(1);
const subtypeSublayerId = parseInt(subtypeSubLayer.subtypeCode);
const legend = new Legend({
  view: view,
  layerInfos: [
    {
      layer: subtypeGroupLayer,
      sublayerIds: [subtypeSublayerId]
    }
  ]
});

respectLayerDefinitionExpression

Property

Type: boolean

Since: ArcGIS Maps SDK for JavaScript 4.30

If a layer uses a unique value render, only features that satisfy the layer's definition expression will be displayed in the legend when set to true.

See also

FeatureLayerBase.definitionExpression

Default value: false

respectLayerVisibility

Property

Type: boolean

Since: ArcGIS Maps SDK for JavaScript 4.13

Determines whether to respect the properties of the layers in the map that control the legend's visibility (minScale, maxScale, legendEnabled). By default, a layer's legend elements will not render in the legend given the following conditions:

The layer's FeatureLayer.legendEnabled property is set to false.
If the view's scale is outside the visibility range defined by the layer's ScaleRangeLayer.minScale and ScaleRangeLayer.maxScale properties.

When the respectLayerVisibility property of the legend is set to false, the legend elements for each layer in the map will always display, thus disregarding the minScale, maxScale, and legendEnabled properties for each layer in the map.

See also

hideLayersNotInCurrentView

Default value: true

Example

// Always displays legend elements for the map's layers
// regardless of their minScale, maxScale, and legendEnabled properties
legend.respectLayerVisibility = false;

style

autocast Property

Type: LegendStyle

Since: ArcGIS Maps SDK for JavaScript 4.7

Indicates the style of the legend. The style determines the legend's layout and behavior. You can either specify a string or an object to indicate the style. The known string values are the same values listed in the table within the type property.

Default value: "classic"

Examples

// renders the legend in the card style with a "stack" layout
legend.style = "card";

// renders the legend in the card style with a responsive
// layout that toggles between "stack" and "side-by-side"
legend.style = {
  type: "card",
  layout: "auto"
};

// renders the legend in the classic layout
legend.style = "classic";

view

Property

Type: MapViewOrSceneView | LinkChartView | null | undefined

A reference to the MapView, LinkChartView, or SceneView. Set this to link the widget to a specific view.

viewModel

autocast Property

Type: LegendViewModel

The view model for this widget. This is a class that contains all the logic (properties and methods) that controls this widget's behavior. See the LegendViewModel class to access all properties and methods on the widget.

visible

inherited Property

Type: boolean

Inherited from: Widget

Indicates whether the widget is visible.

If false, the widget will no longer be rendered in the web document. This may affect the layout of other elements or widgets in the document. For example, if this widget is the first of three widgets associated to the upper right hand corner of the DefaultUI, then the other widgets will reposition when this widget is made invisible. For more information, refer to the css display value of "none".

Default value: true

Example

// Hides the widget in the view
widget.visible = false;

Methods

Method	Signature	Class
`classes` inherited	`classes(...classNames: ((string \| null \| undefined) \| ((string[] \| Record<string, boolean>) \| null \| undefined) \| false \| null \| undefined)[]): string`	Widget
`destroy` inherited	`destroy(): void`	Widget
`emit` inherited	`emit<Type extends EventNames<this>>(type: Type, event?: this["@eventTypes"][Type]): boolean`	EventedMixin
`hasEventListener` inherited	`hasEventListener<Type extends EventNames<this>>(type: Type): boolean`	EventedMixin
`isFulfilled` inherited	`isFulfilled(): boolean`	EsriPromiseMixin
`isRejected` inherited	`isRejected(): boolean`	EsriPromiseMixin
`isResolved` inherited	`isResolved(): boolean`	EsriPromiseMixin
`on` inherited	`on<Type extends EventNames<this>>(type: Type, listener: EventedCallback<this["@eventTypes"][Type]>): ResourceHandle`	EventedMixin
`postInitialize` inherited	`postInitialize(): void`	Widget
`render` inherited	`render(): any \| null`	Widget
`renderNow` inherited	`renderNow(): void`	Widget
`scheduleRender` inherited	`scheduleRender(): void`	Widget
`when` inherited	`when<TResult1 = this, TResult2 = never>(onFulfilled?: OnFulfilledCallback<this, TResult1> \| null \| undefined, onRejected?: OnRejectedCallback<TResult2> \| null \| undefined): Promise<TResult1 \| TResult2>`	EsriPromiseMixin

classes

inherited Method

Signature: classes (...classNames: ((string | null | undefined) | ((string[] | Record<string, boolean>) | null | undefined) | false | null | undefined)[]): string

Inherited from: Widget

Since: ArcGIS Maps SDK for JavaScript 4.7

A utility method used for building the value for a widget's class property. This aids in simplifying css class setup.

Parameters

Parameter	Type	Description	Required
classNames	`((string \| null \| undefined) \| ((string[] \| Record<string, boolean>) \| null \| undefined) \| false \| null \| undefined)[]`	The class names.

Returns: string
The computed class name.

Example

// .tsx syntax showing how to set css classes while rendering the widget

render() {
  const dynamicClasses = {
    [css.flip]: this.flip,
    [css.primary]: this.primary
  };

  return (
    <div class={classes(css.root, css.mixin, dynamicClasses)} />
  );
}

destroy

inherited Method

Signature: destroy (): void

Inherited from: Widget

Destroys the widget instance.

Returns: void

emit

inherited Method

Signature: emit <Type extends EventNames<this>>(type: Type, event?: this["@eventTypes"][Type]): boolean

Type parameters: <Type extends EventNames<this>>

Inherited from: EventedMixin

Since: ArcGIS Maps SDK for JavaScript 4.5

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

Parameters

Parameter	Type	Description	Required
type	`Type`	The name of the event.
event	`this["@eventTypes"][Type]`	The event payload.

Returns: boolean
true if a listener was notified

hasEventListener

inherited Method

Signature: hasEventListener <Type extends EventNames<this>>(type: Type): boolean

Type parameters: <Type extends EventNames<this>>

Inherited from: EventedMixin

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

Parameters

Parameter	Type	Description	Required
type	`Type`	The name of the event.

Returns: boolean
Returns true if the class supports the input event.

isFulfilled

inherited Method

Signature: isFulfilled (): boolean

Inherited from: EsriPromiseMixin

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: boolean
Indicates whether creating an instance of the class has been fulfilled (either resolved or rejected).

isRejected

inherited Method

Signature: isRejected (): boolean

Inherited from: EsriPromiseMixin

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

Returns: boolean
Indicates whether creating an instance of the class has been rejected.

isResolved

inherited Method

Signature: isResolved (): boolean

Inherited from: EsriPromiseMixin

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

Returns: boolean
Indicates whether creating an instance of the class has been resolved.

on

inherited Method

Signature: on <Type extends EventNames<this>>(type: Type, listener: EventedCallback<this["@eventTypes"][Type]>): ResourceHandle

Type parameters: <Type extends EventNames<this>>

Inherited from: EventedMixin

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

Parameters

Parameter	Type	Description	Required
type	`Type`	An event or an array of events to listen for.
listener	`EventedCallback<this["@eventTypes"][Type]>`	The function to call when the event fires.

Returns

ResourceHandle

Returns an event handler with a remove() method that should 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);
});

postInitialize

inherited Method

Signature: postInitialize (): void

Inherited from: Widget

Executes after widget is ready for rendering.

Returns: void

render

inherited Method

Signature: render (): any | null

Inherited from: Widget

This method is implemented by subclasses for rendering.

Returns: any | null
The rendered virtual node.

renderNow

inherited Method

Signature: renderNow (): void

Inherited from: Widget

Renders widget to the DOM immediately.

Returns: void

scheduleRender

inherited Method

Signature: scheduleRender (): void

Inherited from: Widget

Schedules widget rendering. This method is useful for changes affecting the UI.

Returns: void

when

inherited Method

Signature: when <TResult1 = this, TResult2 = never>(onFulfilled?: OnFulfilledCallback<this, TResult1> | null | undefined, onRejected?: OnRejectedCallback<TResult2> | null | undefined): Promise<TResult1 | TResult2>

Type parameters: <TResult1 = this, TResult2 = never>

Inherited from: EsriPromiseMixin

Since: ArcGIS Maps SDK for JavaScript 4.6

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

Parameters

Parameter	Type	Description	Required
onFulfilled	`OnFulfilledCallback<this, TResult1> \| null \| undefined`	The function to call when the promise resolves.
onRejected	`OnRejectedCallback \| null \| undefined`	The function to execute when the promise fails.

Returns: Promise<TResult1 | TResult2>
Returns a new promise for the result of onFulfilled 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
});

Type definitions

StyleType

Type definition

Since: ArcGIS Maps SDK for JavaScript 5.0

Represents the allowed values for the style property, as defined by the type property of the CardView and ClassicView classes.

See also

Type: CardView["type"] | ClassicView["type"]

LegendStyle

Type definition

Since: ArcGIS Maps SDK for JavaScript 5.0

Represents the allowed styles for the style property.

See also

style

Type: CardView | ClassicView

Unique values

Continuous color

Classed color

Continuous size

Size - above and below

Dot density

Predominance

Relationship

Example

Constructors

Parameters

Example

Properties

Example

Examples

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Methods

Parameters

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Type definitions