Legend

require(["esri/widgets/Legend"], function(Legend) { /* code goes here */ });

Class: esri/widgets/Legend

Inheritance: Legend Widget Accessor

Since: ArcGIS API for JavaScript 4.0

The Legend widget displays labels and symbols for layers in a map. Labels and their corresponding symbols depend on the values set in the Renderer of the layer. The legend will only display layers and sublayers that are visible in the view.

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, IntegratedMeshLayer, KMLLayer, OpenStreetMapLayer, GraphicsLayer, GeoRSSLayer, VectorTileLayer, and WebTileLayer
3D symbols with more than one symbol layer are not supported.
DictionaryRenderer is not supported.

For information about gaining full control of widget styles, see the Styling topic.

See also:

Example:

var legend = new Legend({
  view: view,
  layerInfos: [{
    layer: featureLayer,
    title: "Legend"
  }]
});

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

Constructors

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
var 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

Type	Summary	Class
Collection<ActiveLayerInfo>	Collection of ActiveLayerInfo objects used by the legend view to display data in the legend. more details	more details	Legend
Boolean	Indicates whether to show the Basemap layers in the Legend. more details	more details	Legend
String\|HTMLElement	The ID or node representing the DOM element containing the widget. more details	more details	Widget
String	The name of the class. more details	more details	Accessor
Boolean	When `true`, this property indicates whether the widget has been destroyed. more details	more details	Widget
String	The widget's default CSS icon class. more details	more details	Legend
String	The unique ID assigned to the widget when the widget is created. more details	more details	Widget
String	The widget's default label. more details	more details	Legend
Object []	Specifies a subset of the layers to display in the legend. more details	more details	Legend
Boolean	Determines whether to respect the properties of the layers in the map that control the legend's visibility (`minScale`, `maxScale`, `legendEnabled`). more details	more details	Legend
Object\|String	Indicates the style of the legend. more details	more details	Legend
MapView\|SceneView	A reference to the MapView or SceneView. more details	more details	Legend
LegendViewModel	The view model for this widget. more details	more details	Legend

Property Details

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 Boolean

Indicates whether to show the Basemap layers in the Legend.

Default Value:false

Example:

legend.basemapLegendVisible = true;

container String|HTMLElement inherited

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 cases 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 Stringreadonly inherited Since: ArcGIS API for JavaScript 4.7

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

destroyed Boolean inherited

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

iconClass String Since: ArcGIS API for JavaScript 4.7

The widget's default CSS icon class.

id String inherited

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 String Since: ArcGIS API for JavaScript 4.7

The widget's default label.

layerInfos Object []

Specifies a subset of the layers to display in the legend. If this property is not set, all layers in the map will display in the legend. 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.

respectLayerVisibility Boolean Since: ArcGIS API 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 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

Example:

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

style Object|String Since: ArcGIS API 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.

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.

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.

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 MapView|SceneView

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

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.

Method Overview

Show inherited methods Hide inherited methods

Return Type	Summary	Class
String	A utility method used for building the value for a widget's `class` property. more details	more details	Widget
	Destroys the widget instance. more details	more details	Widget
Boolean	Emits an event on the instance. more details	more details	Widget
Boolean	Indicates whether there is an event listener on the instance that matches the provided event name. more details	more details	Widget
Object	Registers an event handler on the instance. more details	more details	Widget
	Widget teardown helper. more details	more details	Widget
	This method is primarily used by developers when implementing custom widgets. more details	more details	Widget
Object	This method is primarily used by developers when implementing custom widgets. more details	more details	Widget
	Renders widget to the DOM immediately. more details	more details	Widget
	This method is primarily used by developers when implementing custom widgets. more details	more details	Widget

Method Details

classes(classNames){String}inherited Since: ArcGIS API 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.

Parameter:

classNames Array<(string|Array<string>|Object)>

repeatable

The class names.

Returns:

Type	Description
String	The computed class name.

See also:

Guide - Widget development (rendering)

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

Destroys the widget instance.

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

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.

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);
});

own(handles)inherited

Widget teardown helper. Any handles added to it will be automatically removed when the widget is destroyed.

Parameter:

handles WatchHandle|WatchHandle []

Handles marked for removal once the widget is destroyed.

postInitialize()inherited

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

render(){Object}inherited

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

Renders widget to the DOM immediately.

scheduleRender()inherited

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

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