Legend

AMD: require(["esri/widgets/Legend"], (Legend) => { /* code goes here */ });
ESM: import Legend from "@arcgis/core/widgets/Legend.js";
Class: esri/widgets/Legend
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

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

Unique values

Unique values

Continuous color

Continuous color

Classed color

Classed color

Continuous size

Continuous size

Size - above and below

Size - above and below

Dot density

Dot density

Predominance

Predominance

Relationship

Relationship

For information about gaining full control of widget styles, see the Styling topic.
See also
Example
let legend = new Legend({
  view: view
});

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

Constructors

Legend

Constructor
new Legend(properties)
Parameter
properties Object
optional

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

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

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
Collection<ActiveLayerInfo>

Collection of ActiveLayerInfo objects used by the legend view to display data in the legend.

Legend
Boolean

Indicates whether to show the Basemap layers in the Legend.

Legend
String|HTMLElement

The ID or node representing the DOM element containing the widget.

Widget
String

The name of the class.

Accessor
Number

Indicates the heading level to use for the legend title.

Legend
Boolean

When true, layers will only be shown in the legend if they are visible in the view's extent.

Legend
String

Icon which represents the widget.

Legend
String

The widget's default CSS icon class.

Legend
String

The unique ID assigned to the widget when the widget is created.

Widget
String

The widget's default label.

Legend
Object[]

Specifies a subset of the layers to display in the legend.

Legend
Boolean

Determines whether to respect the properties of the layers in the map that control the legend's visibility (minScale, maxScale, legendEnabled).

Legend
Object|String

Indicates the style of the legend.

Legend
MapView|SceneView

A reference to the MapView or SceneView.

Legend
LegendViewModel

The view model for this widget.

Legend
Boolean

Indicates whether the widget is visible.

Widget

Property Details

activeLayerInfos

Property
activeLayerInfos Collection<ActiveLayerInfo>autocast
Autocasts from Object[]

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
basemapLegendVisible 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

Inherited
Property
container String|HTMLElement
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

Inherited
Property
declaredClass Stringreadonly
Inherited from Accessor
Since: ArcGIS Maps SDK for JavaScript 4.7 Accessor since 4.0, declaredClass added at 4.7.

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

headingLevel

Property
headingLevel Number
Since: ArcGIS Maps SDK for JavaScript 4.20 Legend since 4.0, headingLevel added at 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.

Default Value:3
See also
Example
// legend title will render as an <h2>
legend.headingLevel = 2;

hideLayersNotInCurrentView

Property
hideLayersNotInCurrentView Boolean
Since: ArcGIS Maps SDK for JavaScript 4.21 Legend since 4.0, hideLayersNotInCurrentView added at 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.

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

Default Value:false
See also
Example
// layers not displayed in the view
// will not be shown in the legend
legend.hideLayersNotInCurrentView = true;

icon

Property
icon String
Since: ArcGIS Maps SDK for JavaScript 4.27 Legend since 4.0, icon added at 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).

Default Value:null
See also

iconClass

Property
iconClass String
Since: ArcGIS Maps SDK for JavaScript 4.7 Legend since 4.0, iconClass added at 4.7.
Deprecated since 4.27. Use icon instead.

The widget's default CSS icon class.

id

Inherited
Property
id 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

Property
label String
Since: ArcGIS Maps SDK for JavaScript 4.7 Legend since 4.0, label added at 4.7.

The widget's default label.

layerInfos

Property
layerInfos Object[]

Specifies a subset of the layers to display in the legend. This includes any basemap layers you want to be visible in the legend. If this property is not set, all layers in the map will display in the legend, including basemap layers if basemapLegendVisible is true. Objects in this array are defined with the properties listed below.

Properties
title String
optional

Specifies a title for the layer to display above its symbols and descriptions. If no title is specified the service name is used.

layer Layer

A layer to display in the legend.

sublayerIds Number[]
optional

Only applicable if the layer is a MapImageLayer, SubtypeGroupLayer or WMSLayer. The IDs of the sublayers for which to display legend information. Since version 4.23.

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]
    }
  ]
});

respectLayerVisibility

Property
respectLayerVisibility Boolean
Since: ArcGIS Maps SDK for JavaScript 4.13 Legend since 4.0, respectLayerVisibility added at 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 legendEnabled property is set to false.
  • If the view's scale is outside the visibility range defined by the layer's minScale and 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.

Default Value:true
See also
Example
// Always displays legend elements for the map's layers
// regardless of their minScale, maxScale, and legendEnabled properties
legend.respectLayerVisibility = false;

style

Property
style Object|String
Since: ArcGIS Maps SDK for JavaScript 4.7 Legend since 4.0, style added at 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.

Properties
type String

Specifies the style of the legend. There are two possible values listed in the table below:

Value Description
classic The legend has a portrait orientation. The user can scroll vertically when many elements are included in the legend's content.
card In wide views, the legend has a landscape orientation that allows users to scroll horizontally to view all legend elements. This style can be responsive, making it ideal for mobile web apps. In smaller views, the legend collapses to occupy less space. One element is shown at a time in a card-style layout, which the user can navigate horizontally.

Possible Values:"classic"|"card"

layout String
optional
Default Value:stack

When a card type is specified, you can specify one of the following layout options.

Value Description
auto This layout is responsive so that in wide views the legend has a side-by-side layout, and a stack layout in smaller (mobile) views.
side-by-side The legend has a landscape orientation that allows users to scroll horizontally to view multiple legend cards at a time.
stack The legend cards are stacked, which conserves space, but restricts the user to seeing only one card at a time.

Possible Values:"auto"|"side-by-side"|"stack"

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
view MapView|SceneView

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

viewModel

Property
viewModel LegendViewModelautocast

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
visible 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 view UI, 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;

Method Overview

Show inherited methods Hide inherited methods
Name Return Type Summary Class

Adds one or more handles which are to be tied to the lifecycle of the object.

Accessor
String

A utility method used for building the value for a widget's class property.

Widget

Destroys the widget instance.

Widget
Boolean

Emits an event on the instance.

Widget
Boolean

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

Widget
Boolean

Returns true if a named group of handles exist.

Accessor
Boolean

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

Widget
Boolean

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

Widget
Boolean

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

Widget
Object

Registers an event handler on the instance.

Widget

Adds one or more handles which are to be tied to the lifecycle of the widget.

Widget

This method is primarily used by developers when implementing custom widgets.

Widget

Removes a group of handles owned by the object.

Accessor
Object

This method is primarily used by developers when implementing custom widgets.

Widget

Renders widget to the DOM immediately.

Widget

This method is primarily used by developers when implementing custom widgets.

Widget
Promise

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

Widget

Method Details

addHandles

Inherited
Method
addHandles(handleOrHandles, groupKey)
Inherited from Accessor
Since: ArcGIS Maps SDK for JavaScript 4.25 Accessor since 4.0, addHandles added at 4.25.

Adds one or more handles which are to be tied to the lifecycle of the object. The handles will be removed when the object is destroyed.

// Manually manage handles
const handle = reactiveUtils.when(
  () => !view.updating,
  () => {
    wkidSelect.disabled = false;
  },
  { once: true }
);

this.addHandles(handle);

// Destroy the object
this.destroy();
Parameters
handleOrHandles WatchHandle|WatchHandle[]

Handles marked for removal once the object is destroyed.

groupKey *
optional

Key identifying the group to which the handles should be added. All the handles in the group can later be removed with Accessor.removeHandles(). If no key is provided the handles are added to a default group.

classes

Inherited
Method
classes(classNames){String}
Inherited from Widget
Since: ArcGIS Maps SDK for JavaScript 4.7 Widget since 4.2, classes added at 4.7.

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

Parameter
classNames String|String[]|Object
repeatable

The class names.

Returns
Type Description
String The computed class name.
Example
// .tsx syntax showing how to set css classes while rendering the widget

render() {
  const dynamicIconClasses = {
    [css.myIcon]: this.showIcon,
    [css.greyIcon]: !this.showIcon
  };

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

destroy

Inherited
Method
destroy()
Inherited from Widget

Destroys the widget instance.

emit

Inherited
Method
emit(type, event){Boolean}
Inherited from Widget
Since: ArcGIS Maps SDK for JavaScript 4.5 Widget since 4.2, emit added at 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

hasEventListener

Inherited
Method
hasEventListener(type){Boolean}
Inherited from Widget

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.

hasHandles

Inherited
Method
hasHandles(groupKey){Boolean}
Inherited from Accessor
Since: ArcGIS Maps SDK for JavaScript 4.25 Accessor since 4.0, hasHandles added at 4.25.

Returns true if a named group of handles exist.

Parameter
groupKey *
optional

A group key.

Returns
Type Description
Boolean Returns true if a named group of handles exist.
Example
// Remove a named group of handles if they exist.
if (obj.hasHandles("watch-view-updates")) {
  obj.removeHandles("watch-view-updates");
}

isFulfilled

Inherited
Method
isFulfilled(){Boolean}
Inherited from Widget
Since: ArcGIS Maps SDK for JavaScript 4.19 Widget since 4.2, isFulfilled added at 4.19.

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

Inherited
Method
isRejected(){Boolean}
Inherited from Widget
Since: ArcGIS Maps SDK for JavaScript 4.19 Widget since 4.2, isRejected added at 4.19.

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

Inherited
Method
isResolved(){Boolean}
Inherited from Widget
Since: ArcGIS Maps SDK for JavaScript 4.19 Widget since 4.2, isResolved added at 4.19.

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.

on

Inherited
Method
on(type, listener){Object}
Inherited from Widget

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

Parameters

An event or an array of events to listen for.

listener Function

The function to call when the event fires.

Returns
Type Description
Object 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);
});

own

Inherited
Method
own(handleOrHandles)
Inherited from Widget
Since: ArcGIS Maps SDK for JavaScript 4.24 Widget since 4.2, own added at 4.24.
Deprecated since 4.28 Use addHandles() instead.

Adds one or more handles which are to be tied to the lifecycle of the widget. The handles will be removed when the widget is destroyed.

const handle = reactiveUtils.when(
  () => !view.updating,
  () => {
    wkidSelect.disabled = false;
  },
  { once: true}
);

this.own(handle); // Handle gets removed when the widget is destroyed.
Parameter
handleOrHandles WatchHandle|WatchHandle[]

Handles marked for removal once the widget is destroyed.

postInitialize

Inherited
Method
postInitialize()
Inherited from Widget

This method is primarily used by developers when implementing custom widgets. Executes after widget is ready for rendering.

removeHandles

Inherited
Method
removeHandles(groupKey)
Inherited from Accessor
Since: ArcGIS Maps SDK for JavaScript 4.25 Accessor since 4.0, removeHandles added at 4.25.

Removes a group of handles owned by the object.

Parameter
groupKey *
optional

A group key or an array or collection of group keys to remove.

Example
obj.removeHandles(); // removes handles from default group

obj.removeHandles("handle-group");
obj.removeHandles("other-handle-group");

render

Inherited
Method
render(){Object}
Inherited from Widget

This method is primarily used by developers when implementing custom widgets. It must be implemented by subclasses for rendering.

Returns
Type Description
Object The rendered virtual node.

renderNow

Inherited
Method
renderNow()
Inherited from Widget

Renders widget to the DOM immediately.

scheduleRender

Inherited
Method
scheduleRender()
Inherited from Widget

This method is primarily used by developers when implementing custom widgets. Schedules widget rendering. This method is useful for changes affecting the UI.

when

Inherited
Method
when(callback, errback){Promise}
Inherited from Widget
Since: ArcGIS Maps SDK for JavaScript 4.19 Widget since 4.2, when added at 4.19.

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.
Example
// Although this example uses the BasemapGallery widget, any class instance that is a promise may use when() in the same way
let bmGallery = new BasemapGallery();
bmGallery.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
});

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