LayerList

AMD: require(["esri/widgets/LayerList"], (LayerList) => { /* code goes here */ });
ESM: import LayerList from "@arcgis/core/widgets/LayerList";
Class: esri/widgets/LayerList
Inheritance: LayerList Widget Accessor
Since: ArcGIS API 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.

To hide layers in the map from the LayerList widget, you must set the listMode property on the desired layers to hide.

For information about gaining full control of widget styles, see the Styling topic.
See also:
Example:
let 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

new LayerList(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 layerlist = new LayerList({
  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
String|HTMLElementmore details

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

more detailsWidget
Stringmore details

The name of the class.

more detailsAccessor
Stringmore details

The widget's default CSS icon class.

more detailsLayerList
Stringmore details

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

more detailsWidget
Stringmore details

The widget's default label.

more detailsLayerList
ListItemCreatedHandlermore details

A function that executes each time a ListItem is created or modified.

more detailsLayerList
Booleanmore details

Indicates whether more than one list item may be selected by the user at a single time.

more detailsLayerList
Collection<ListItem>more details

A collection of ListItems representing operational layers.

more detailsLayerList
Collection<ListItem>more details

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

more detailsLayerList
Booleanmore details

Indicates whether list items may be selected by the user.

more detailsLayerList
MapView|SceneViewmore details

A reference to the MapView or SceneView.

more detailsLayerList
LayerListViewModelmore details

The view model for this widget.

more detailsLayerList
Booleanmore details

Indicates whether the widget is visible.

more detailsWidget
VisibleElementsmore details

The visible elements that are displayed within the widget.

more detailsLayerList

Property Details

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.

iconClass String
Since: ArcGIS API for JavaScript 4.7

The widget's default CSS icon class.

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.

listItemCreatedFunction ListItemCreatedHandler
Since: ArcGIS API for JavaScript 4.4

A function that executes each time a ListItem is created or modified. 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 actionsSections property of the ListItem.

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

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

    let item = event.item;

    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"
      }]];
    }
  }
});
multipleSelectionEnabled Boolean

Indicates whether more than one list item may be selected by the user at a single time. You must first set selectionEnabled to true for this property to have an effect on the widget.

Selected items are available in the selectedItems property.

Default Value:false
See also:
Example:
layerList.selectionEnabled = true;
layerList.multipleSelectionEnabled = true;
operationalItems Collection<ListItem>readonly

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

See also:
selectedItems Collection<ListItem>

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

See also:
selectionEnabled Boolean

Indicates whether list items may be selected by the user. Selected items may be reordered in the list by dragging gestures with the mouse or touch screen, or with arrow keys on the keyboard.

Selected items are available in the selectedItems property.

Default Value:false
See also:
Example:
layerList.selectionEnabled = true;

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

viewModel 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.

visible Boolean inherited

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;
visibleElements VisibleElementsautocast
Since: ArcGIS API 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 = {
  statusIndicators: false
};

Method Overview

Show inherited methods Hide inherited methods
Name Return Type Summary Class
Stringmore details

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

more detailsWidget
more details

Destroys the widget instance.

more detailsWidget
Booleanmore details

Emits an event on the instance.

more detailsWidget
Booleanmore details

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

more detailsWidget
Booleanmore details

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

more detailsWidget
Booleanmore details

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

more detailsWidget
Booleanmore details

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

more detailsWidget
Objectmore details

Registers an event handler on the instance.

more detailsWidget
more details

Widget teardown helper.

more detailsWidget
more details

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

more detailsWidget
Objectmore details

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

more detailsWidget
more details

Renders widget to the DOM immediately.

more detailsWidget
more details

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

more detailsWidget
more details

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

more detailsLayerList
Promisemore details

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

more detailsWidget

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 String|String[]|Object
repeatable

The class names.

Returns:
Type Description
String The computed class name.
See also:
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.
isFulfilled(){Boolean}inherited
Since: ArcGIS API for JavaScript 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(){Boolean}inherited
Since: ArcGIS API for JavaScript 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(){Boolean}inherited
Since: ArcGIS API for JavaScript 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(type, listener){Object}inherited

Registers an event handler on the instance. Call this method to hook an event with a listener. See the Events summary table for a list of supported events.

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(handles)inherited

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

Parameter:

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.

triggerAction(action, item)

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

Parameters:

The action to execute.

item ListItem

An item associated with the action.

when(callback, errback){Promise}inherited
Since: ArcGIS API for JavaScript 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 that may be used to chain additional functions.
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
});

Type Definitions

ListItemCreatedHandler(event)

Function definition for the listItemCreatedFunction property. See the example snippet in the listItemCreatedFunction documentation for more details.

Parameters:
event Object

An object containing a list item created by the LayerList.

Specification:
item ListItem

A list item created by the LayerList. You can modify the properties of this item to customize the text, actions, panel content, and visibility of the list item. See the documentation for the listItemCreatedFunction for more details.

VisibleElements

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

Property:
statusIndicators Boolean
optional

Indicates whether the status indicators will be displayed. Default is true.

Event Overview

Name Type Summary Class
{action: ActionButton,ActionToggle,item: ListItem}
more details

Fires after the user clicks on an action or action toggle inside the LayerList widget.

more details LayerList

Event Details

trigger-action

Fires after the user clicks on an action or action toggle inside the LayerList widget. This event may be used to define a custom function to execute when particular actions are clicked.

Properties:

The action clicked by the user.

item ListItem

The ListItem associated with the action.

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