Widget

Class: esri/widgets/Widget
Inheritance: Widget Accessor
Since: ArcGIS API for JavaScript 4.2

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 Hide inherited properties
Name Type Summary Class
String|HTMLElement

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

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String

The name of the class.

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String

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

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String

The widget's label.

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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

Name Return Type Summary Class
String

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

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Destroys the widget instance.

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Boolean

Emits an event on the instance.

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Boolean

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

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Boolean

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

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Boolean

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

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Boolean

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

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Object

Registers an event handler on the instance.

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Widget teardown helper.

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

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Object

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

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Renders widget to the DOM immediately.

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

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Promise

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

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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:
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:

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 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
});

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