Widget

The base class for widgets. Each widget's presentation is separate from its properties, methods, and data.

The separation of core logic and presentation makes each widget highly customizable when working with other frameworks and libraries such as Bootstrap, React, and JQuery.

The properties and methods of each widget are handled in its viewModel property, which is an Accessor-based class. Since each view model class extends Accessor, all properties on the widget can be accessed using the methods outlined in the Working with properties topic.

This design allows developers to create new widgets and repurpose existing widgets with a third party framework. Separation of a widget's presentation and core logic also means developers can use the logic without having to render its UI components. More information about creating custom widgets is available in the Widget development Guide topic.

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

See also:

Property Overview

Any properties can be set, retrieved or listened to. See the Working with Properties topic.

Show inherited properties

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Type	Summary	Class
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
String	The unique ID assigned to the widget when the widget is created. more details	more details	Widget
String	The widget's label. more details	more details	Widget

Property Details

container String|HTMLElement

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.

id String

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 4.11

The widget's label.

This property is useful whenever the widget is controlled by another one (e.g. Expand)

Method Overview

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
Boolean	`isFulfilled()` may be used to verify if creating an instance of the class is fulfilled (either resolved or rejected). more details	more details	Widget
Boolean	`isRejected()` may be used to verify if creating an instance of the class is rejected. more details	more details	Widget
Boolean	`isResolved()` may be used to verify if creating an instance of the class is resolved. 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
Promise	`when()` may be leveraged once an instance of the class is created. more details	more details	Widget

Method Details

classes(classNames){String} 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:

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()

Destroys the widget instance.

emit(type, event){Boolean} 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}

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} 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} 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} 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}

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)

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()

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

render(){Object}

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()

Renders widget to the DOM immediately.

scheduleRender()

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

when(callback, errback){Promise} 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
});

ArcGIS API for JavaScriptAPI Reference

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