ComboBox

A text input paired with a popup that can be used as an alternative to typing
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Demo: Like all combo boxes, AutoCompleteComboBox has a text input and an associated popup

Overview

The combo box user interface pattern combines the free-form nature of a text area with the convenience of a popup that can be used to populate the text. The popup can help make the user aware of what kinds of text responses are appropriate, and offer them input controls they can click or tap as an alternative to typing.

For example, the popup in the AutoCompleteComboBox above, and other variations of ListComboBox, is some form of ListBox presenting a list of common text responses. In contrast, the popup in a DateComboBox is a CalendarMonthNavigator for selecting a date:

Demo: DateComboBox uses a CalendarMonthNavigator as its popup

See also

AutoCompleteComboBox
A combo box that auto-completes the user's input against the list items
DateComboBox
Combo box that lets the user type a date or pick one from a popup calendar
FilterComboBox
A combo box which applies its text input as a filter on its list items
ListBox
Single-selection list box
ListComboBox
A combo box whose popup presents a list of choices
MenuButton
A button that invokes a menu

API

Ancestry: ComboBox → PopupSourceReactiveElement → HTMLElement

Built with mixins AriaRoleMixin, AriaRoleMixin, AttributeMarshallingMixin, DelegateFocusMixin, DisabledMixin, FocusVisibleMixin, FormElementMixin, KeyboardMixin, KeyboardMixin, OpenCloseMixin, ReactiveMixin, and ShadowTemplateMixin.

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

Extended by classes AutoCompleteComboBox, DateComboBox, FilterComboBox, and ListComboBox.

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: (component class constructor)|HTMLTemplateElement|string

Default: Backdrop

Defined by PopupSource

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: objectan indication of how or why the element closed

Defined by OpenCloseMixin

closed property

True if the element is currently closed.

Type: boolean

Defined by OpenCloseMixin

closed event

Raised when the component closes.

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

disabled property

True if the component is disabled, false (the default) if not.

The value of this property will be reflected to the disabled attribute so that it can be referenced in CSS. Note that this non-native implementation of the disabled attribute will not trigger the :disabled CSS pseudo-class, so your style rules will have to reference the presence or absence of the disabled attribute. That is, instead of writing

my-component:disabled { ... }

write this instead

my-component[disabled] { ... }

Like the native disabled attribute, this attribute is boolean. That means that it's existence in markup sets the attribute, even if set to an empty string or a string like "false".

Type: boolean

Default: false

Defined by DisabledMixin

form property

The ID of the form element with which this element is associated, or null if the element is not associated with any form. This is provided for consistency with the native HTML form property.

Type: string

Defined by FormElementMixin

frameRole property

The class, tag, or template used to contain the popup content.

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

Type: (component class constructor)|HTMLTemplateElement|string

Default: OverlayFrame

Defined by PopupSource

horizontalAlign property

The alignment of the popup with respect to the source button.

  • start: popup and source are aligned on the leading edge according to the text direction
  • end: popup and source are aligned on the trailing edge according to the text direction
  • left: popup and source are left-aligned
  • right: popup and source are right-aligned
  • `stretch: both left and right edges are aligned

Type: 'start'|'end'|'left'|'right'|'stretch'

Default: 'start'

Defined by PopupSource

input property

The combo box's input element.

Type: Element|null

inputRole property

The class, tag, or template used to create the input element.

Type: (component class constructor)|HTMLTemplateElement|string

Default: 'input'

[internal.defaultState] property

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

Type: State

Defined by ReactiveMixin

[internal.delegatesFocus] property

Returns true if the component is delegating its focus.

A component using DelegateFocusMixin will always have this property be true unless a class takes measures to override it.

Type: boolean

Default: true

Defined by DelegateFocusMixin

[internal.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[internal.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[internal.ids].foo is the same as this.shadowRoot.getElementById('foo').

Type: object

Defined by ShadowTemplateMixin

[internal.keydown]() method

See the symbols documentation for details.

Defined by KeyboardMixin

[internal.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: objectdictionary of flags indicating which state members have changed since the last render

Defined by ReactiveMixin

[internal.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 all internal render methods, then invokes componentDidMount (for first render) or componentDidUpdate (for subsequent renders).

Defined by ReactiveMixin

[internal.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: objectthe changes to apply to the element's state

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

Defined by ReactiveMixin

[internal.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: State

Defined by ReactiveMixin

name property

The name of the form field that will be filled with this element's value. This is an analogue of the standard HTML name property.

Type: string

Defined by FormElementMixin

open() method

Open the element (if not already opened).

Defined by OpenCloseMixin

opened property

True if the element is currently opened.

Type: boolean

Defined by OpenCloseMixin

opened event

Raised when the component opens.

Defined by OpenCloseMixin

opened-changed event

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

Defined by OpenCloseMixin

placeholder property

The prompt text shown in the input if it is empty.

Type: string

popupPosition property

The preferred direction for the popup.

  • above: popup should appear above the source
  • below: popup should appear below the source

Type: 'above'|'below'

Default: 'below'

Defined by PopupSource

popupRole property

The class, tag, or template used to define the popup.

The popup element is responsible for handling overlay behavior.

Type: (component class constructor)|HTMLTemplateElement|string

Default: Popup

Defined by PopupSource

sourceRole property

The class, tag, or template used for the button (or other element) that will invoke the popup.

Type: (component class constructor)|HTMLTemplateElement|string

Default: 'button'

Defined by PopupSource

suppressFocusVisibility() method

Temporarily suppress visibility of the keyboard focus until the next keydown event.

This can be useful in components like Menu that actively manage where the focus is in response to mouse hover activity. If the user uses the keyboard to invoke a menu, then changes to using the mouse, it can be distracting to see the focus indicator moving as well. In such situations, the component can invoke this method (e.g., in response to mousemove) to temporarily suppress focus visibility.

Defined by FocusVisibleMixin

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

toggleButtonRole property

The class, tag, or template used to create the button that toggles the popup.

Type: (component class constructor)|HTMLTemplateElement|string

Default: SeamlessButton

type property

The "type" of the form field, provided for consistency with the native HTML type property. The value of this property will be the same as the HTML tag name registered for the custom element.

Type: string

Defined by FormElementMixin

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