AlertDialog

A type of Dialog optimized for asking a single question the user can respond to with a small set of choices.

Demo: Some simple AlertDialog examples

Usage

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.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.

API

$ property

The collection of references to the elements with IDs 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.

Such references simplify a component's access to its own elements. In exchange, this mixin trades off a one-time cost of querying all elements in the shadow tree instead of paying an ongoing cost to query for an element each time the component wants to inspect or manipulate it.

These shadow element references are established the first time you read the $ property. They are * not updated if you subsequently modify the shadow tree yourself (to replace one item with another, to add new items with id attributes, etc.).

Type: object

Defined by ShadowTemplateMixin inherited from ElementBase

choiceButtons 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.

You can use any strings for the choices. AlertDialog provides static properties offering two simple arrays of choices for common situations:

  • OK: an array with the single choice "OK".
  • OK_CANCEL: an array with two choices, "OK" and “Cancel”.

You can use these to set the choices property, or you can provide custom choices:

// Create an OK/Cancel alert.
const alert = new AlertDialog();
alert.choices = AlertDialog.OK_CANCEL;

Type: Array.<string>

choices property

The choices to present to the user.

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

Type: Array.<string>

close(result) 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 result parameter. This result will be made available in the whenClosed promise and the state.result member.

Parameters:
  • result: objectan indication of how or why the element closed

Defined by OpenCloseMixin inherited from Dialog

closed property

True if the element is currently closed.

Type: boolean

Defined by OpenCloseMixin inherited from Dialog

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 inherited from Dialog

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 inherited from ElementBase

open() method

Open the element (if not already opened).

Defined by OpenCloseMixin inherited from Dialog

opened property

True if the element is currently closed.

Type: boolean

Defined by OpenCloseMixin inherited from Dialog

opened-changed event

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

Defined by OpenCloseMixin inherited from Dialog

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 inherited from ElementBase

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.

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

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

Defined by ReactiveMixin inherited from ElementBase

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.

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

Parameters:
  • nextState: objectthe proposed new state for the element

Defined by ReactiveMixin inherited from ElementBase

state property

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

Type: object

Defined by ReactiveMixin inherited from ElementBase

symbols.keydown() method

See the symbols documentation for details.

Defined by KeyboardMixin inherited from Dialog

toggle(opened) method

Toggle the open/close state of the element.

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

Defined by OpenCloseMixin inherited from Dialog

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 inherited from ElementBase

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 inherited from Dialog

wrap(template) static method

Wrap a base template with elements necessary to capture focus.

Call this method in a components symbols.template property.

Note: The wrap method hangs off of FocusCaptureMixin like a static method; the mixin does not add it to an element's prototype chain. Accordingly, you must invoke this method as FocusCaptureMixin.wrap(template), not this.wrap(template).

Returns: string a template that includes left/right arrow buttons

Parameters:
  • template: stringfor the element(s) controlled by the arrow buttons

Defined by FocusCaptureMixin inherited from Dialog

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