Asks a single question the user can answer with choice buttons

Demo: Some simple AlertDialog examples


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.


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

const dialog = new AlertDialog();
dialog.textContent = 'Hello, world';
dialog.choices = ['OK', 'Cancel'];;
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.


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


Ancestry: AlertDialog → DialogOverlayReactiveElement → HTMLElement

Built with mixins AttributeMarshallingMixin, DialogModalityMixin, KeyboardMixin, OpenCloseMixin, OverlayMixin, ReactiveMixin, RenderUpdatesMixin, and ShadowTemplateMixin.

By default, this uses these elements in the following roles:

$ 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.$.foo to obtain the corresponding button in the component instance's shadow tree. The $ function is simply a shorthand for getElementById, so this.$.foo is the same as this.shadowRoot.getElementById('foo').

Type: object

Defined by ShadowTemplateMixin

backdropRole property

The class, tag, or template used for the optional backdrop element 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: function|string|HTMLTemplateElement

Default: Backdrop

Defined by Overlay

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.


  • closeResult: objectan indication of how or why the element closed

Defined by OpenCloseMixin

closed event

Raised when the component closes.

Defined by OpenCloseMixin

closed property

True if the element is currently closed.

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

defaultState property

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

Type: object

Defined by ReactiveMixin

frameRole property

The class, tag, or template used to contain the primary overlay 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: function|string|HTMLTemplateElement

Default: OverlayFrame

Defined by Overlay

open() method

Open the element (if not already opened).

Defined by OpenCloseMixin

opened event

Raised when the component opens.

Defined by OpenCloseMixin

opened property

True if the element is currently opened.

Type: boolean

Defined by OpenCloseMixin

opened-changed event

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

Defined by OpenCloseMixin

refineState(state) method

Apply changes to a proposed new state for the component to enforce necessary consistency between state members. See Refining state for details.


  • state: objecta proposed new state for the component

Returns: boolean - true if the state is already acceptable as it is

Defined by ReactiveMixin

render() method

Render the component to the DOM.

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

This method invokes all internal render methods. It then invoked componentDidMount (for first render) or componentDidUpdate (for subsequent renders).

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.


  • changes: objectthe changes to apply to the element's state

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

Defined by ReactiveMixin

shouldComponentUpdate(nextState) method

Return true if the component should update.

The default implementation does a shallow check of property values like React's PureComponent. This seems adequate for most web components. You can override this to always return true (like React's base Component class), or to perform more specific, deeper checks for changes in state.


  • nextState: objectthe proposed new state for the element

Returns: boolean - true if the component should update (rerender)

Defined by ReactiveMixin

state property

The component's current state. The returned state object is immutable. To update it, invoke setState.

Type: object

Defined by ReactiveMixin

symbols.keydown() method

See the symbols documentation for details.

Defined by KeyboardMixin

toggle(opened) method

Toggle the open/close state of the element.


  • opened: booleantrue if the element should be opened, false if closed.

Defined by OpenCloseMixin

updates property

The attributes and properies that should be applied to the component on render. By default, this is an empty plain object. Your mixin or component can extend this to identify the properties to set on the host element or elements in the shadow subtree.

Type: object

Defined by RenderUpdatesMixin

whenClosed() method

This method can be used as an alternative to listening to the "opened-changed" 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