Carousel

A typical carousel with a sliding effect, left/right arrow buttons, and page dots.

Mountain lake Terraced farm Winter trees Forest river Red panda
Demo: A Carousel

The user can move between items with touch, the mouse, the keyboard, or a trackpad.

Carousel uses a SlidingStage as the "stage" for rendering the featured or selected item. The left/right arrow buttons are provided by ArrowDirectionMixin.

By default, each item in the list is represented with a simple PageDot as a proxy element. The related CarouselWithThumbnails represents items with a Thumbnail proxy instead of a dot. You can also supply custom proxy elements used to represent the items.

Mountain lake Terraced farm Winter trees Forest river Red panda Snowy peaks Stone arch Snowy river Palm trees Sunset through palm trees River canyon Lake with milky water Dirt road lined with fallen leaves Iceberg River at sunrise Coastal mountains Hoodoo formations Sandy beach Autumn foliage on mountainside Sunset over rocky ocean pool
Demo: A CarouselWithThumbnails

For a carousel that supports the same types of navigation, but without arrows, dots, or other adornments, see SlidingPages.

Mountain lake Terraced farm Winter trees Forest river Red panda
Demo: SlidingPages provides no visible adornments

The CarouselSlideshow variation adds a timer for slideshow functionality.

Mountain lake Terraced farm Winter trees Forest river Red panda
Demo: CarouselSlideshow

Carousel uses ArrowDirectionMixin to create the left and right arrow buttons. See that mixin for customization options.

Carousel incorporates LanguageDirectionMixin so that it can flip the order of items in right-to-left languages. See that page for a demonstration.

Usage

import Carousel from 'elix/src/Carousel.js';
const carousel = new Carousel(); // or
const carousel = document.createElement('elix-carousel');

In HTML:

<script type="module" src="node_modules/elix/src/Carousel.js"></script>
<elix-carousel>
  <!-- Carousel items such as img elements go here. -->
  <img src="image1.jpg">
  <img src="image2.jpg">
  <img src="image3.jpg">
  <img src="image4.jpg">
  <img src="image5.jpg">
</elix-carousel>

Carousel is appropriate when:

  • You want to present to the user a collection of images, or a mixture of graphical and textual content.
  • You want to let the user focus on a single item at a time.
  • The number of items is small (2–10). The Carousel will create a PageDot for each item, which would be unweildy for larger collections. If you have a large collection of images to show, it might be better to use CarouselWithThumbnails or SlidingPages directly.

API

Ancestry: Carousel → ExplorerReactiveElement → HTMLElement

Built with mixins AriaListMixin, ArrowDirectionMixin, AttributeMarshallingMixin, DirectionSelectionMixin, FocusVisibleMixin, KeyboardDirectionMixin, KeyboardMixin, LanguageDirectionMixin, LanguageDirectionMixin, ReactiveMixin, RenderUpdatesMixin, ShadowTemplateMixin, SingleSelectionMixin, SlotItemsMixin, SwipeDirectionMixin, TouchSwipeMixin, and TrackpadSwipeMixin.

Includes subelements PageDot, CenteredStripOpacity, SlidingStage, and ArrowDirectionButton.

Extended by classes CarouselSlideshow and CarouselWithThumbnails.

$ 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 ReactiveElement

arrowButtonTag property

The tag used to create the left and right arrow buttons.

Type: string

Default: 'elix-arrow-direction-button'

Defined by ArrowDirectionMixin

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 inherited from Explorer

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 inherited from Explorer

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 ReactiveElement

inject(template) method

Add the arrow buttons to a template.

Parameters:
  • template: stringthe inner template placed inside the button container

Defined by ArrowDirectionMixin

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 inherited from SlotItemsMixin

items property

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

Defined by ContentItemsMixin inherited from SlotItemsMixin

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 inherited from SlotItemsMixin

proxies property

The current set of proxy elements that correspond to the component's main items. If you have assigned elements to the proxy slot, this returns the collection of those elements. Otherwise, this will return a collection of default proxies generated by the component, one for each item.

Type: Array.

Inherited from Explorer

proxyListOverlap property

True if the list of proxies should overlap the stage, false if not.

Type: boolean

Default: {false}

Inherited from Explorer

proxyListPosition property

The position of the proxy list relative to the stage.

The start and end values refer to text direction: in left-to-right languages such as English, these are equivalent to left and right, respectively.

Type: 'bottom', 'end', 'left', 'right', 'start', 'top'

Default: 'start'

Inherited from Explorer

proxyListTag property

The tag used to create the Explorer's list of proxies.

Type: string

Default: 'div'

Inherited from Explorer

proxyTag property

The tag used to create default proxies for the list items.

Type: string

Default: 'div'

Inherited from Explorer

proxyUpdates(proxy, calcs) method

Determine what updates should be applied to a proxy to reflect the state of the corresponding item, 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 proxy during rendering.

The calcs parameter is an object with the following members:

  • index: the index of this proxy in the list.
  • isDefaultProxy: true if this proxy was generated by the Explorer, false if the proxy was assigned to the Explorer's proxy slot.
  • item: the list item corresponding to this proxy. E.g., for a tab button, the item is the corresponding tab panel.

Parameters:
  • proxy: Elementthe proxy to be updated
  • calcs: objectper-proxy calculations derived from element state

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

Inherited from Explorer

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 inherited from ReactiveElement

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 ReactiveElement

selected-index-changed event

Raised when the selectedIndex property changes.

Defined by SingleSelectionMixin inherited from Explorer

selectedIndex property

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

Type: number

Defined by SingleSelectionMixin inherited from Explorer

selectedItem property

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

Type: Element

Defined by SingleSelectionMixin inherited from Explorer

selectFirst() method

Select the first item in the list.

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

Defined by SingleSelectionMixin inherited from Explorer

selectionRequired property

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

Type: boolean

Default: false

Defined by SingleSelectionMixin inherited from Explorer

selectionWraps property

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

Type: boolean

Default: false

Defined by SingleSelectionMixin inherited from Explorer

selectLast() method

Select the last item in the list.

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

Defined by SingleSelectionMixin inherited from Explorer

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 inherited from Explorer

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 inherited from Explorer

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 inherited from ReactiveElement

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 inherited from ReactiveElement

stageTag property

The tag used to create the main "stage" element showing a single item at a time.

Type: string

Default: 'elix-modes'

Inherited from Explorer

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 ReactiveElement

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.goDown() method

Invokes selectNext to select the next item.

Defined by DirectionSelectionMixin

symbols.goDown() method

Invoked when the user wants to go/navigate down. The default implementation of this method does nothing.

Defined by KeyboardDirectionMixin

symbols.goEnd() method

Invoked when the user wants to go/navigate to the end (e.g., of a list). The default implementation of this method does nothing.

Defined by KeyboardDirectionMixin

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.goLeft() method

Invoked when the user wants to go/navigate left. The default implementation of this method does nothing.

Defined by KeyboardDirectionMixin

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.goRight() method

Invoked when the user wants to go/navigate right. The default implementation of this method does nothing.

Defined by KeyboardDirectionMixin

symbols.goStart() method

Invokes selectFirst to select the first item.

Defined by DirectionSelectionMixin

symbols.goStart() method

Invoked when the user wants to go/navigate to the start (e.g., of a list). The default implementation of this method does nothing.

Defined by KeyboardDirectionMixin

symbols.goUp() method

Invokes selectPrevious to select the previous item.

Defined by DirectionSelectionMixin

symbols.goUp() method

Invoked when the user wants to go/navigate up. The default implementation of this method does nothing.

Defined by KeyboardDirectionMixin

symbols.keydown() method

See the symbols documentation for details.

Defined by KeyboardMixin

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 ReactiveElement