LayerList | References | ArcGIS Maps SDK for JavaScript

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

Inheritance:: LayerList→Widget→Accessor

Since: ArcGIS Maps SDK for JavaScript 4.2

The LayerList widget provides a way to display a list of layers, and switch on/off their visibility. The ListItem API provides access to each layer's properties, allows the developer to configure actions related to the layer, and allows the developer to add content to the item related to the layer.

Notes

The LayerList does not emit an event when the visibility of a layer changes. To respond to layer visibility changes, watch the Layer.visible property or the Map.allLayers property with reactiveUtils. To hide layers in the map from the LayerList widget, you must set the Layer.listMode property on the desired layers to hide. When a KnowledgeGraphLayer is present in the map, the LayerList widget will display the KnowledgeGraphLayer.tables as a tableList ListItem. When a CatalogLayer is present in the map, the LayerList widget will display the CatalogLayer.dynamicGroupLayer in a catalogLayerList ListItem.

See also

Example

const layerList = new LayerList({
  view: view
});
// Adds widget below other elements in the top left corner of the view
view.ui.add(layerList, {
  position: "top-left"
});

Constructors

Constructor

Parameters

Parameter	Type	Description	Required
properties	`LayerListProperties`

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

Example

// typical usage
const layerlist = new LayerList({
  view
});

Properties

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

Property	Type	Class
`catalogLayerList` readonly	`CatalogLayerList \| null \| undefined`
`catalogOptions`	`CatalogLayerListProperties \| null \| undefined`
`collapsed`	`boolean`
`container` inherited	`HTMLElement \| null \| undefined`	Widget
`declaredClass` readonly inherited	`string`	Accessor
`destroyed` readonly inherited	`boolean`	Widget
`dragEnabled`	`boolean`
`filterPlaceholder`	`string`
`filterPredicate`	`FilterPredicate \| null \| undefined`
`filterText`	`string`
`headingLevel`	`HeadingLevel`
`icon`	`Icon["icon"]`
`id` inherited	`string`	Widget
`knowledgeGraphOptions`	`TableListProperties \| null \| undefined`
`label`	`string`
`listItemCreatedFunction`	`ListItemModifier \| null \| undefined`
`minDragEnabledItems`	`number`
`minFilterItems`	`number`
`openedLayers` readonly	`Collection<FlowLayer>`
`operationalItems`	`Collection<ListItem>`
`selectedItems`	`Collection<ListItem>`
`selectionMode`	`"multiple" \| "single" \| "none" \| "single-persist"`
`tableList` readonly	`TableList \| null \| undefined`
`uid` readonly inherited	`string`	IdentifiableMixin
`view`	`MapViewOrSceneView \| null \| undefined`
`viewModel`	`LayerListViewModel`
`visibilityAppearance`	`VisibilityAppearance`
`visible` inherited	`boolean`	Widget
`visibleElements`	`LayerListVisibleElements`

catalogLayerList

readonly Property

Type: CatalogLayerList | null | undefined

Since: ArcGIS Maps SDK for JavaScript 4.30

The CatalogLayerList widget instance that displays a catalog layer's dynamic group layer. The catalog layer list will be displayed as an expandable ListItem in the LayerList widget. This property is set when a catalog layer's dynamic group layer is expanded in the LayerList. Otherwise, it is null. This list item will only be displayed when catalog layers are loaded in the map and will be displayed as a child of the catalog layer. This property is useful for listening to the CatalogLayerList.@trigger-action event and managing selections in catalog layers.

CatalogLayerList

See also

catalogOptions

Example

// Use reactiveUtils to respond to the layerList.catalogLayerList "trigger-action" event
reactiveUtils.on(
  () => layerList.catalogLayerList,
  "trigger-action",
  async (event) => {
    if (event.action.id === "add-layer") {
      // Get the parent catalog layer
      const parentCatalogLayer = catalogUtils.getCatalogLayerForLayer(event.item.layer);
      // Get the footprint from the parent catalog layer
      const footprint = parentCatalogLayer.createFootprintFromLayer(event.item.layer);
      // Get the layer from the footprint
      const layerFromFootprint = await parentCatalogLayer.createLayerFromFootprint(footprint);
      // Add the layer to the map
      map.add(layerFromFootprint);
      // back out of the catalog layer list to the main layer list
      layerList.openedLayers.pop();
    }
  }
);

// Use reactiveUtils to watch for a selected item in the layerList.catalogLayerList
reactiveUtils.watch(
  () => layerList.catalogLayerList?.selectedItems.at(0)?.layer,
  (layer) => {
    // When a layer is selected log out its title
    if (layer) {
      console.log(layer.title);
    }
  }
);

catalogOptions

Property

Type: CatalogLayerListProperties | null | undefined

Since: ArcGIS Maps SDK for JavaScript 4.30

CatalogLayer specific properties. Catalog layers will display their CatalogLayer.dynamicGroupLayer as an expandable catalogLayerList in the LayerList widget. This list item will only be displayed when catalog layers with dynamic group layers are loaded in the map. These are the properties that are used to configure the catalogLayerList.

See also

catalogLayerList

Example

const layerList = new LayerList({
  catalogOptions: {
    listItemCreatedFunction: (event) => {
      const { item } = event;
      item.actionsSections = [
        [
          {
            title: "Add layer to map",
            icon: "add-layer",
            id: "add-layer"
          }
        ]
      ];
    },
    selectionMode: "single",
    visibleElements: {
      filter: true
    }
  },
  view,
});

collapsed

Property

Type: boolean

Since: ArcGIS Maps SDK for JavaScript 4.29

Indicates whether the widget is collapsed. When collapsed, only the collapse button and heading are displayed.

See also

visibleElements.collapseButton

Default value: false

Example

layerList.collapsed = 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.

dragEnabled

Property

Type: boolean

Since: ArcGIS Maps SDK for JavaScript 4.29

Indicates whether list items may be reordered within the list by dragging and dropping. MapImageLayer MapImageLayer.sublayers can be reordered only within their parent MapImageLayer and can not be dragged out as a separate layer. Drag won't be enabled until the number of list items is equal to or greater than than the value set set in minDragEnabledItems.

See also

minDragEnabledItems

Default value: false

Example

layerList.dragEnabled = true;

filterPlaceholder

Property

Type: string

Since: ArcGIS Maps SDK for JavaScript 4.29

Placeholder text used in the filter input if visibleElements.filter is true.

See also

visibleElements.filter

Default value: ""

Example

layerList.filterPlaceholder = "Filter layers";

filterPredicate

Property

Type: FilterPredicate | null | undefined

Since: ArcGIS Maps SDK for JavaScript 4.32

Specifies a function to handle filtering list items.

Example

layerList.filterPredicate = (item) => item.title.toLowerCase().includes("streets");

filterText

Property

Type: string

Since: ArcGIS Maps SDK for JavaScript 4.29

The value of the filter input if visibleElements.filter is true.

See also

visibleElements.filter

Default value: ""

Example

reactiveUtils.watch(
  () => layerList.filterText,
  (filterText) => console.log(filterText)
);

headingLevel

Property

Type: HeadingLevel

Since: ArcGIS Maps SDK for JavaScript 4.29

Indicates the heading level to use for the heading of the widget. By default, the heading is rendered as a level 2 heading (e.g., <h2>Layer List</h2>). Depending on the widget's placement in your app, you may need to adjust this heading for proper semantics. This is important for meeting accessibility standards.

See also

visibleElements.heading

Default value: 2

Example

layerList.headingLevel = 3;

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: "layers"

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.

knowledgeGraphOptions

Property

Type: TableListProperties | null | undefined

Since: ArcGIS Maps SDK for JavaScript 4.30

KnowledgeGraphLayer specific properties. Knowledge graph layers will display KnowledgeGraphLayer.tables as an expandable tableList in the LayerList widget. This tables list item will only be displayed when knowledge graph layers with tables are loaded in the map. These are the properties that are used to configure the tableList.

See also

tableList

Example

layerList.knowledgeGraphOptions = {
  filterPlaceholder: "Filter tables",
  listItemCreatedFunction: (event) => {
    const { item } = event;
    item.actionsSections = [
      [
        {
          icon: "table",
          id: "open-table",
          title: "Show table"
        },
        {
          icon: "information",
          id: "information",
          title: "Show information"
        }
      ]
    ];
  },
  minFilterItems: 1,
  visibleElements: {
    errors: true,
    filter: true,
    statusIndicators: true
  }
}

label

autocast Property

Type: string

Since: ArcGIS Maps SDK for JavaScript 4.7

The widget's default label.

listItemCreatedFunction

Property

Type: ListItemModifier | null | undefined

Since: ArcGIS Maps SDK for JavaScript 4.4

A function that executes each time a ListItem is created. Use this function to add actions and panels to list items, and to override the default settings of a list item. Actions can be added to list items using the ListItem.actionsSections property of the ListItem.

See also

Sample - LayerList widget with actions

Example

let layerList = new LayerList({
  view: view,
  // executes for each ListItem in the LayerList
  listItemCreatedFunction: async function (event) {

    // The event object contains properties of the
    // layer in the LayerList widget.

    let item = event.item;

    // Wait for the layer to load and the item title to become available
    await item.layer.when();

    if (item.title === "US Demographics") {
      // open the list item in the LayerList
      item.open = true;
      // change the title to something more descriptive
      item.title = "Population by county";
      // set an action for zooming to the full extent of the layer
      item.actionsSections = [[{
        title: "Go to full extent",
        className: "esri-icon-zoom-out-fixed",
        id: "full-extent"
      }]];
    }
  }
});

minDragEnabledItems

Property

Type: number

Since: ArcGIS Maps SDK for JavaScript 4.29

The minimum number of list items required to enable drag and drop reordering with dragEnabled.

See also

dragEnabled

Default value: 2

Example

layerList.dragEnabled = true;
layerList.minDragEnabledItems = 5;

minFilterItems

Property

Type: number

Since: ArcGIS Maps SDK for JavaScript 4.29

The minimum number of list items required to display the visibleElements.filter input box.

See also

visibleElements.filter

Default value: 10

Example

layerList.visibleElements.filter = true;
layerList.minFilterItems = 5;

openedLayers

readonly Property

Type: Collection<FlowLayer>

Since: ArcGIS Maps SDK for JavaScript 4.31

A collection of Layers that are opened in a catalogLayerList or tableList flow item. This property is useful for backing out of the catalog layer list or table list programmatically to the parent layer list.

See also

Default value: []

Example

// back out of the catalog layer list to the main layer list
layerList.openedLayers.pop();

operationalItems

Property

Type: Collection<ListItem>

A collection of ListItems representing operational layers. To hide layers from the LayerList widget, set the Layer.listMode property on the layer(s) to hide.

See also

Layer.listMode

selectedItems

Property

Type: Collection<ListItem>

A collection of selected ListItems representing operational layers selected by the user.

See also

selectionMode

selectionMode

Property

Type: "multiple" | "single" | "none" | "single-persist"

Since: ArcGIS Maps SDK for JavaScript 4.29

Specifies the selection mode. Selected items are available in the selectedItems property.

Value	Description
multiple	Allows any number of items to be selected at once. This is useful when you want to apply an operation to multiple items at the same time.
none	Disables selection. Use this when you want to prevent selecting items.
single	Allows only one item to be selected at a time. If another item is selected, the previous selection is cleared. This is useful when you want to ensure that a maximum of one item is selected at a time.
single-persist	Allows only one item to be selected at a time and prevents de-selection. Once an item is selected, it remains selected until another item is selected. This is useful when you want to ensure that there is always exactly one selected item.

See also

selectedItems

Default value: "none"

Example

layerList.selectionMode = "multiple";

tableList

readonly Property

Type: TableList | null | undefined

Since: ArcGIS Maps SDK for JavaScript 4.30

The TableList widget instance that displays the tables associated with a KnowledgeGraphLayer. The table list will be displayed as an expandable ListItem in the LayerList widget. This property is set when a knowledge graph layer's tables ListItem is expanded in the LayerList. Otherwise, it is null. This list item will only be displayed when knowledge graph layers with tables are loaded in the map and will be displayed as a child of the knowledge graph layer. This property is useful for listening to the TableList.@trigger-action event and managing selections in knowledge graph tables.

tableList

See also

knowledgeGraphOptions

Example

// Use reactiveUtils to respond to the layerList.tableList "trigger-action" event
reactiveUtils.on(
  () => layerList.tableList,
  "trigger-action",
  (event) => {
    if (event.action.id === "open-table") {
      // Open the table in the FeatureTable widget
      featureTable.layer = event.item.layer;
      // Back out of the table list to the layer list
      layerList.openedLayers.pop();
    }
  }
);

// Use reactiveUtils to watch for a selected item in the layerList.tableList
reactiveUtils.watch(
  () => layerList.tableList?.selectedItems.at(0)?.layer,
  (layer) => {
    // When a layer is selected log out its title
    if (layer) {
       console.log(layer.title);
    }
  }
);

uid

readonlyinherited Property

Type: string

Inherited from: IdentifiableMixin

Since: ArcGIS Maps SDK for JavaScript 4.33

An automatically generated unique identifier assigned to the instance. The unique id is generated each time the application is loaded.

view

Property

Type: MapViewOrSceneView | null | undefined

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

viewModel

autocast Property

Type: LayerListViewModel

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 LayerListViewModel class to access all properties and methods on the widget.

visibilityAppearance

Property

Type: VisibilityAppearance

Since: ArcGIS Maps SDK for JavaScript 4.29

Determines the icons used to indicate visibility.

Value	Description	Example
default	Displays view icons on the far side. Icons are hidden except on hover or if they have keyboard focus. See view-visible and view-hide calcite icons.
checkbox	Displays checkbox icons on the near side. See check-square-f and square calcite icons.

Default value: "default"

Example

layerList.visibilityAppearance = "checkbox";

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;

visibleElements

autocast Property

Type: LayerListVisibleElements

Since: ArcGIS Maps SDK for JavaScript 4.15

The visible elements that are displayed within the widget. This property provides the ability to turn individual elements of the widget's display on/off.

Example

layerList.visibleElements = {
  catalogLayerList: true,
  closeButton: false,
  collapseButton: true,
  errors: true,
  filter: true,
  heading: true,
  statusIndicators: true
};

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
`triggerAction`	`triggerAction(action: Action, item: ListItem): void`
`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

triggerAction

Method

Signature: triggerAction (action: Action, item: ListItem): void

Triggers the @trigger-action event and executes the given action or action toggle.

Parameters

Parameter	Type	Description	Required
action	`Action`	The action to execute.
item	`ListItem`	An item associated with the action.

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
});

Events

Name	Type
`trigger-action` inherited	CustomEvent<LayerListViewModelTriggerActionEvent>

trigger-action

inherited Event

trigger-action: CustomEvent<LayerListViewModelTriggerActionEvent>

Inherited from: LayerListViewModelEvents

Emitted when the user clicks an action or action toggle in a layer list. Use this event to run custom logic when a specific action is triggered.

See also

Type definitions

SubtablesLayer

Type definition

Since: ArcGIS Maps SDK for JavaScript 5.0

Represents a layer type that supports displaying associated tables within the LayerList.

See also

openedLayers

Type: KnowledgeGraphLayer | MapImageLayer | TileLayer

FlowLayer

Type definition

Since: ArcGIS Maps SDK for JavaScript 5.0

Represents a layer that can be displayed in a separate flow item within the LayerList.

See also

openedLayers

Type: SubtablesLayer | CatalogLayer