ListBox

Single-selection list box
Acai
Akee
Apple
Apricot
Avocado
Banana
Bilberry
Black sapote
Blackberry
Blackcurrant
Blood orange
Blueberry
Boysenberry
Cantaloupe
Cherimoya
Cherry
Chico fruit
Clementine
Cloudberry
Coconut
Crab apple
Cranberry
Cucumber
Currant
Damson
Date
Dragonfruit
Durian
Elderberry
Feijoa
Fig
Goji berry
Gooseberry
Grape
Grapefruit
Guava
Honeyberry
Honeydew
Horned melon
Huckleberry
Jabuticaba
Jackfruit
Jambul
Japanese plum
Jostaberry
Jujube
Juniper berry
Kiwifruit
Kumquat
Lemon
Lime
Longan
Loquat
Lychee
Mandarine
Mango
Mangosteen
Marionberry
Miracle fruit
Mulberry
Nance
Nectarine
Orange
Papaya
Passionfruit
Peach
Pear
Persimmon
Pineapple
Pineberry
Plantain
Plum
Pluot
Pomegranate
Pomelo
Purple mangosteen
Quince
Rambutan
Raspberry
Redcurrant
Salak
Salal berry
Salmonberry
Satsuma
Soursop
Star apple
Star fruit
Strawberry
Surinam cherry
Tamarillo
Tamarind
Tangerine
Ugli fruit
Watermelon
White currant
White sapote
Yuzu
Demo: Typical single-selection list box

Overview

This component presents its assigned children as items in a single-selection list box. This is modeled after the list box controls in macOS and Microsoft Windows, and the standard select element in HTML in its list box mode.

ListBox uses SingleSelectionMixin to expose a single selection. The user can click an item to select it, or navigate the selection with the keyboard (per KeyboardDirectionMixin, KeyboardPagedSelectionMixin, and KeyboardPrefixSelectionMixin).

By default, a ListBox shows a generic visual style. The selected item is shown with standard highlight colors (CSS highlight color for the background, highlighttext for the text). You can create custom subclasses of ListBox that override the updates property to provide custom styling.

The ListBox exposes an orientation property that can either by "vertical" (the default), or "horizontal". Internally, the orientation is tracked as state.orientation.

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Demo: A horizontal list

The ListBox applies SelectedItemTextValueMixin (below) to expose a value property.

Lists typically obtain their items from their child elements using SlotContentMixin. However, it is easy to create variations of ListBox for lists with hard-coded content. The custom list box below uses the same mixins as ListBox, but omits SlotContentMixin. Instead, it draws its content from a hard-coded set of items in its template.

Demo: A list with hard-coded items

You could create such components in cases where you want to ensure a particular set of items is always provided.

ListBox is also incorporated into other components, such as ListExplorer or ListComboBox:

Pet:
Canary
Cat
Chicken
Chinchilla
Cockatiel
Cricket
Dog
Ferret
Finch
Fish
Frog
Gerbil
Guinea Pig
Hamster
Hermit Crab
Lizard
Mouse
Parakeet
Parrot
Pig
Rabbit
Rat
Snail
Snake
Spider
Turtle
Demo: AutoCompleteComboBox includes a ListBox in a popup

A subclass of ListBox, FilterListBox, is used in ListWithSearch and applies a text filter to show only items that contain the indicated text:

Acai
Akee
Apple
Apricot
Avocado
Banana
Bilberry
Black sapote
Blackberry
Blackcurrant
Blood orange
Blueberry
Boysenberry
Cantaloupe
Cherimoya
Cherry
Chico fruit
Clementine
Cloudberry
Coconut
Crab apple
Cranberry
Cucumber
Currant
Damson
Date
Dragonfruit
Durian
Elderberry
Feijoa
Fig
Goji berry
Gooseberry
Grape
Grapefruit
Guava
Honeyberry
Honeydew
Horned melon
Huckleberry
Jabuticaba
Jackfruit
Jambul
Japanese plum
Jostaberry
Jujube
Juniper berry
Kiwifruit
Kumquat
Lemon
Lime
Longan
Loquat
Lychee
Mandarine
Mango
Mangosteen
Marionberry
Miracle fruit
Mulberry
Nance
Nectarine
Orange
Papaya
Passionfruit
Peach
Pear
Persimmon
Pineapple
Pineberry
Plantain
Plum
Pluot
Pomegranate
Pomelo
Purple mangosteen
Quince
Rambutan
Raspberry
Redcurrant
Salak
Salal berry
Salmonberry
Satsuma
Soursop
Star apple
Star fruit
Strawberry
Surinam cherry
Tamarillo
Tamarind
Tangerine
Ugli fruit
Watermelon
White currant
White sapote
Yuzu
Demo: ListWithSearch can filter the items in the list

Usage

import ListBox from 'elix/src/ListBox.js';
const listBox = new ListBox(); // or
const listBox = document.createElement('elix-list-box');

In HTML:

<script type="module" src="node_modules/elix/src/ListBox.js"></script>
<elix-list-box>
  <!-- List items go here -->
</elix-list-box>

Single-selection list boxes are common in user interfaces. As written, the ListBox component supports the same use cases as a standard select element in list box mode (with the size attribute set to a value greater than 1). The standard select, however, has many constraints on what can be done with it, forcing developers to recreate much of its functionality. The advantage of providing ListBox as a web component is that developers are free to extend it to meet the needs of their interface. For example, one use case for ListBox is a horizontal list (instead of the fixed vertical orientation provided by select).

See also

API

Ancestry: ListBox → ReactiveElement → HTMLElement

Built with mixins AriaListMixin, AttributeMarshallingMixin, ClickSelectionMixin, ComposedFocusMixin, DirectionSelectionMixin, FocusVisibleMixin, ItemsTextMixin, KeyboardDirectionMixin, KeyboardMixin, KeyboardPagedSelectionMixin, KeyboardPrefixSelectionMixin, LanguageDirectionMixin, ReactiveMixin, RenderUpdatesMixin, SelectedItemTextValueMixin, SelectionInViewMixin, ShadowTemplateMixin, SingleSelectionMixin, and SlotItemsMixin.

Extended by class FilterListBox.

This element is used to fill a role in AutoCompleteComboBox, Explorer, ListComboBox, and ListExplorer.

$ 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

canSelectNext property

True if the selection can be moved to the next item, false if not (the selected item is the last item in the list).

Type: boolean

Defined by SingleSelectionMixin

canSelectPrevious property

True if the selection can be moved to the previous item, false if not (the selected item is the first one in the list).

Type: boolean

Defined by SingleSelectionMixin

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

getIndexOfItemAtY() method

Return the item whose content spans the given y position (relative to the top of the list's scrolling client area), or null if not found.

If downward is true, move down the list of items to find the first item found at the given y position; if downward is false, move up the list of

items to find the last item at that position.

Defined by KeyboardPagedSelectionMixin

itemCalcs(item, index) method

Returns a set of calculations about the given item that can be derived from the component's current state.

The goal of the itemCalcs step is to ensure that all mixins/classes use a consistent definition for facts about an item that can be derived from component state. By default, itemCalcs includes a member index containing the index of the indicated item. Other mixins/classes can extend the result of itemCalcs to include additional facts.

For example, the SingleSelectionMixin tracks selection at the component level through a state member state.selectedIndex. When rendering a specific item, a component generally wants to know, "Is this specific item the one which is selected?". SingleSelectionMixin does this with a defintion for itemCalcs that looks like this:

itemCalcs(item, index) {
  const base = super.itemCalcs ? super.itemCalcs(item, index) : null;
  return Object.assign({}, base, {
    selected: index === this.selectedIndex
  });
}

This ensures that any other aspect of the component that wants to inspect the selected state of a given item uses a consistent definition for selection.

Parameters:

  • item: Elementthe item being considered
  • index: numberthe item's position in the list

Defined by ContentItemsMixin

items property

The current set of items drawn from the element's current state.

Defined by ContentItemsMixin

items-changed event

Raised when the items property changes.

Defined by ContentItemsMixin

itemUpdates(item, calcs, original) method

Determine what updates should be applied to an item to reflect the current state, using the format defined by the updates helpers.

By default, this returns an empty object. You should override this method (or use mixins that override this method) to indicate what updates should be applied to the given item during rendering.

Example: AriaListMixin uses code similar to the following to have an item's aria-selected attribute reflect its selection state:

itemUpdates(item, calcs, original) {
  const base = super.itemUpdates ? super.itemUpdates(item, calcs, original) : {};
  return merge(base, {
    attributes: {
      'aria-selected': calcs.selected
    },
  });
}

This code fragment is intended for use with SingleSelectionMixin, which provides the calcs.selected member.

Parameters:

  • item: Elementthe item to be updated
  • calcs: objectper-item calculations derived from element state
  • original: objectthe item's original HTML attributes, classes, and style

Returns: object the DOM updates that should be applied to the item

Defined by ContentItemsMixin

KeyboardPagedSelection#symbols.scrollTarget property

Type: HTMLElement

Defined by KeyboardPagedSelectionMixin

pageDown() method

Scroll down one page.

Defined by KeyboardPagedSelectionMixin

pageUp() method

Scroll up one page.

Defined by KeyboardPagedSelectionMixin

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.

Parameters:

  • 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

scrollOnePage() method

Move by one page downward (if downward is true), or upward (if false). Return true if we ended up changing the selection, false if not.

Defined by KeyboardPagedSelectionMixin

scrollSelectionIntoView() method

Scroll the selected item element completely into view, minimizing the degree of scrolling performed.

Blink has a scrollIntoViewIfNeeded() function that does something similar, but unfortunately it's non-standard, and in any event often ends up scrolling more than is absolutely necessary.

This scrolls the containing element defined by the scrollTarget property. By default, it will scroll the element itself.

Defined by SelectionInViewMixin

selected-index-changed event

Raised when the selectedIndex property changes.

Defined by SingleSelectionMixin

selectedIndex property

The index of the currently-selected item, or -1 if no item is selected.

Type: number

Defined by SingleSelectionMixin

selectedItem property

The currently-selected item, or null if no item is selected.

Type: Element

Defined by SingleSelectionMixin

selectFirst() method

Select the first item in the list.

Returns: Boolean True if the selection changed, false if not.

Defined by SingleSelectionMixin

selectionRequired property

True if the list should always have a selection (if it has items).

Type: boolean

Default: false

Defined by SingleSelectionMixin

selectionWraps property

True if selection navigations wrap from last to first, and vice versa.

Type: boolean

Default: false

Defined by SingleSelectionMixin

selectItemWithTextPrefix(prefix) method

Select the first item whose text content begins with the given prefix.

Parameters:

  • prefix: stringThe prefix string to search for

Returns: boolean

Defined by KeyboardPrefixSelectionMixin

selectLast() method

Select the last item in the list.

Returns: Boolean True if the selection changed, false if not.

Defined by SingleSelectionMixin

selectNext() method

Select the next item in the list.

If the list has no selection, the first item will be selected.

Returns: Boolean True if the selection changed, false if not.

Defined by SingleSelectionMixin

selectPrevious() method

Select the previous item in the list.

If the list has no selection, the last item will be selected.

Returns: Boolean True if the selection changed, false if not.

Defined by SingleSelectionMixin

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

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.

Parameters:

  • 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

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

symbols.canGoLeft property

Returns true if it's currently possible to go left.

Type: boolean

Defined by DirectionSelectionMixin

symbols.canGoRight property

Returns true if it's currently possible to go right.

Type: boolean

Defined by DirectionSelectionMixin

symbols.contentSlot property

Defined by SlotContentMixin

symbols.goDown() method

Invokes selectNext to select the next item.

Defined by DirectionSelectionMixin

symbols.goEnd() method

Invokes selectLast to select the next item.

Defined by DirectionSelectionMixin

symbols.goLeft() method

Invokes selectPrevious to select the previous item.

If the element has a rightToLeft property and it is true, then this selects the next item.

Defined by DirectionSelectionMixin

symbols.goRight() method

Invokes selectNext to select the next item.

If the element has a rightToLeft property and it is true, then this selects the previous item.

Defined by DirectionSelectionMixin

symbols.goStart() method

Invokes selectFirst to select the first item.

Defined by DirectionSelectionMixin

symbols.goUp() method

Invokes selectPrevious to select the previous item.

Defined by DirectionSelectionMixin

symbols.keydown() method

See the symbols documentation for details.

Defined by KeyboardMixin

symbols.rightToLeft property

Type: boolean

Defined by LanguageDirectionMixin

symbols.scrollTarget property

The element that should be scrolled to get the selected item into view.

By default, this uses the defaultScrollTarget helper to find the most likely candidate for scrolling. You can override this property to directly identify which element should be scrolled.

See also symbols.scrollTarget.

Defined by SelectionInViewMixin

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

value property

The text content of the selected item.

Setting this value to a string will attempt to select the first list item whose text content match that string. Setting this to a string not matching any list item will result in no selection.

Type: string

Defined by SelectedItemTextValueMixin