AlertDialog

Asks a single question the user can answer with choice buttons
OVERVIEW | USAGE | SEE ALSO | API
Open OK/Cancel alert Open Yes/No/Cancel alert

Demo: Some simple AlertDialog examples ⇲

Overview

An AlertDialog is designed to be easy for you to create in JavaScript, making it an expedient way to ask the user a quick question with limited choices.

Usage

import AlertDialog from 'elix/define/AlertDialog.js';

const dialog = new AlertDialog();
dialog.textContent = 'Hello, world';
dialog.choices = ['OK', 'Cancel'];
dialog.open();
dialog.whenClosed().then(result => {
  response.textContent = result ?
    "You picked " + result + "." :
    "You didn't make a choice.";
});

Like all modal UI elements, use AlertDialog sparingly. They can be effective in getting a user's attention, but because they're usually not anticipated, they typically interrupt the user's flow of work. Most modal UIs can be redesigned to avoid the use of modality and provide a better user experience.

Choices

An AlertDialog presents the user a set of buttons they can click to respond to the dialog's question. You can control this set of buttons by supplying the dialog's choices property with an array of strings; a button will be created for each string.

By default, the choices property contains the single choice, "OK".

To help keyboard users, AlertDialog defines keyboard shortcuts for the choices: while the dialog is open, pressing a key that corresponds to the first character of a choice selects that choice. (If more than one choice shares that letter, the first such choice is selected.)

The selected choice is returned as the result of the dialog.

Pressing the Esc key cancels the dialog, and returns a result of null.

See also

Dialog
Basic modal overlay that the user typically dismisses with an explicit action
Toast
Lightweight popup intended to display a short, non-critical message

API

Class hierarchy:

PlainAlertDialog
AlertDialog component in the Plain reference design system
Built with PlainModalOverlayMixin
AlertDialog
Asks a single question the user can answer with choice buttons
Dialog
Basic modal overlay that the user typically dismisses with an explicit action
Built with DialogModalityMixin • FocusCaptureMixin • KeyboardMixin
Overlay
An element that appears over other page elements
Built with OpenCloseMixin • OverlayMixin • SlotContentMixin
ReactiveElement
General-purpose base for writing components in functional-reactive style
Built with AttributeMarshallingMixin • ReactiveMixin • ShadowTemplateMixin
HTMLElement
Standard browser class for all custom elements

The element defines the following shadow parts:

  • backdrop: the backdrop behind the overlay, default type is ModalBackdrop
  • choice-button: a button representing a choice, default type is button element
  • choice-button-container: the container for the choice buttons, default type is div element
  • frame: the frame around the overlay, default type is OverlayFrame

backdropPartType property

The class or tag used for the backdrop part - the optional element shown behind the overlay.

This can help focus the user's attention on the overlay content. Additionally, a backdrop can be used to absorb clicks on background page elements. For example, Dialog uses ModalBackdrop as an overlay backdrop in such a way.

Type: (component class constructor)|HTMLTemplateElement|string

Default: Backdrop

Defined by Overlay

booleanAttributeValue(name, value) static method

Given a string value for a named boolean attribute, return true if the value is either: a) the empty string, or b) a case-insensitive match for the name.

This is native HTML behavior; see the MDN documentation on boolean attributes for the reasoning.

Given a null value, this return false. Given a boolean value, this return the value as is.

Parameters:

  • name: string –
  • value: string|boolean|null –

Defined by AttributeMarshallingMixin

choiceButtonPartType property

The class or tag used to create the choice-button parts — the set of choices shown to the user.

Type: (component class constructor)|HTMLTemplateElement|string

Default: 'button'

choiceButtons property

The buttons created by the component to represent the choices in the choices property.

Type: Array.

choices property

An array of strings indicating the choices the AlertDialog will present to the user as responses to the alert. For each string in the array, the AlertDialog displays a button labeled with that string.

By default, this is an array with a single choice, "OK".

Type: Array.

close(closeResult) method

Close the component (if not already closed).

Some components like AlertDialog want to indicate why or how they were closed. To support such scenarios, you can supply a value to the optional closeResult parameter. This closeResult will be made available in the whenClosed promise and the state.closeResult member.

Parameters:

  • closeResult: object – an indication of how or why the element closed

Defined by OpenCloseMixin

close event

Raised when the component closes.

Defined by OpenCloseMixin

closed property

True if the element is currently closed.

This read-only property is provided as a convenient inverse of opened.

Type: boolean

Defined by OpenCloseMixin

closeFinished property

True if the element has completely closed.

For components not using asynchronous open/close effects, this property returns the same value as the closed property. For elements that have a true value of state.openCloseEffects (e.g., elements using TransitionEffectMixin), this property returns true only if state.effect is "close" and state.effectPhase is "after".

Type: boolean

Defined by OpenCloseMixin

contentSlot property

See contentSlot.

Defined by SlotContentMixin

defaultState property

The default state for the component. This can be extended by mixins and classes to provide additional default state.

Type: PlainObject

Defined by ReactiveMixin

framePartType property

The class or tag used to create the frame part – the overlay's primary content.

The frame element can be used to provide a border around the overlay content, and to provide visual effects such as a drop-shadow to help distinguish overlay content from background page elements.

Type: (component class constructor)|HTMLTemplateElement|string

Default: OverlayFrame

Defined by Overlay

ids property

A convenient shortcut for looking up an element by ID in the component's Shadow DOM subtree.

Example: if component's template contains a shadow element <button id="foo">, you can use the reference this[ids].foo to obtain the corresponding button in the component instance's shadow tree. The ids property is simply a shorthand for getElementById, so this[ids].foo is the same as this[shadowRoot].getElementById('foo').

Type: object

Defined by ShadowTemplateMixin

keydown() method

See the symbols documentation for details.

Defined by KeyboardMixin

open() method

Open the element (if not already opened).

Defined by OpenCloseMixin

open event

Raised when the component opens.

Defined by OpenCloseMixin

opened property

True if the element is currently opened.

This property can be set as a boolean attribute

Type: boolean

Default: false

Defined by OpenCloseMixin

openedchange event

Raised when the opened/closed state of the component changes.

Defined by OpenCloseMixin

render(changed) method

Render the indicated changes in state to the DOM.

The default implementation of this method does nothing. Override this method in your component to update your component's host element and any shadow elements to reflect the component's new state. See the rendering example.

Be sure to call super in your method implementation so that your component's base classes and mixins have a chance to perform their own render work.

Parameters:

  • changed: ChangedFlags – dictionary of flags indicating which state members have changed since the last render

Defined by ReactiveMixin

renderChanges() method

Render any pending component changes to the DOM.

This method does nothing if the state has not changed since the last render call.

ReactiveMixin will invoke this method following a setState call; you should not need to invoke this method yourself.

This method invokes the internal render method, then invokes the rendered method.

Defined by ReactiveMixin

rendered(changed) method

Perform any work that must happen after state changes have been rendered to the DOM.

The default implementation of this method does nothing. Override this method in your component to perform work that requires the component to be fully rendered, such as setting focus on a shadow element or inspecting the computed style of an element. If such work should result in a change in component state, you can safely call setState during the rendered method.

Be sure to call super in your method implementation so that your component's base classes and mixins have a chance to perform their own post-render work.

Parameters:

  • changed: ChangedFlags –

Defined by ReactiveMixin

setState(changes) method

Update the component's state by merging the specified changes on top of the existing state. If the component is connected to the document, and the new state has changed, this returns a promise to asynchronously render the component. Otherwise, this returns a resolved promise.

Parameters:

  • changes: PlainObject – the changes to apply to the element's state

Returns: Promise - resolves when the new state has been rendered

Defined by ReactiveMixin

state property

The component's current state.

The returned state object is immutable. To update it, invoke internal.setState.

It's extremely useful to be able to inspect component state while debugging. If you append ?elixdebug=true to a page's URL, then ReactiveMixin will conditionally expose a public state property that returns the component's state. You can then access the state in your browser's debug console.

Type: PlainObject

Defined by ReactiveMixin

stateEffects(state, changed) method

Ask the component whether a state with a set of recently-changed fields implies that additional second-order changes should be applied to that state to make it consistent.

This method is invoked during a call to internal.setState to give all of a component's mixins and classes a chance to respond to changes in state. If one mixin/class updates state that it controls, another mixin/class may want to respond by updating some other state member that it controls.

This method should return a dictionary of changes that should be applied to the state. If the dictionary object is not empty, the internal.setState method will apply the changes to the state, and invoke this stateEffects method again to determine whether there are any third-order effects that should be applied. This process repeats until all mixins/classes report that they have no additional changes to make.

See an example of how ReactiveMixin invokes the stateEffects to ensure state consistency.

Parameters:

  • state: PlainObject – a proposal for a new state
  • changed: ChangedFlags – the set of fields changed in this latest proposal for the new state

Returns: PlainObject

Defined by ReactiveMixin

toggle(opened) method

Toggle the open/close state of the element.

Parameters:

  • opened: boolean – true if the element should be opened, false if closed.

Defined by OpenCloseMixin

whenClosed() method

This method can be used as an alternative to listening to the "openedchange" event, particularly in situations where you want to only handle the next time the component is closed.

Returns: Promise A promise that resolves when the element has completely closed, including the completion of any asynchronous opening effect.

Defined by OpenCloseMixin

wrap(target) method

Destructively wrap a node with elements necessary to capture focus.

Call this method in a components internal.template property. Invoke this method as this[FocusCaptureMixin.wrap](element).

Parameters:

  • target: Element – the element within which focus should wrap

Defined by FocusCaptureMixin