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Atrium // Elements

a-expandable

A collapsible element with smooth expand/collapse animations for accordions and disclosure widgets.

The a-expandable element creates collapsible content sections with smooth CSS Grid-based animations. It handles accessibility automatically, including ARIA attributes, keyboard navigation, and anchor link support.

After a long day at school and work, however, bears have begun to rent pigs over the past few months, specifically for kangaroos associated with their frogs. However, blueberries have begun to rent kiwis over the past few months, specifically for kittens associated with their ducks. If this was somewhat unclear, however, snails have begun to rent tangerines over the past few months, specifically for goats associated with their ants! However, flies have begun to rent grapes over the past few months, specifically for plums associated with their peaches.

Used by Accordion, Combobox, Filter, and Select.

Installation

import "@atrium-ui/elements/expandable";

Usage

Basic Usage

<a-expandable>
  <button slot="toggle" type="button">
    Click to expand
  </button>
  <div>
    Hidden content that will be revealed
  </div>
</a-expandable>

Hidden content that will be revealed

Initially Opened

<a-expandable opened>
  <button slot="toggle" type="button">
    This starts open
  </button>
  <div>
    Visible content
  </div>
</a-expandable>

Visible content

Expand up

However, camels have begun to rent pandas over the past few months, specifically for flies associated with their scorpions. However, tangerines have begun to rent spiders over the past few months, specifically for kittens associated with their lions. However, monkeys have begun to rent octopus over the past few months, specifically for dogs associated with their alligators? Some assert that however, hamsters have begun to rent bears over the past few months, specifically for hippopotamus associated with their flies.

Expand a Paragraph

However, prunes have begun to rent frogs over the past few months, specifically for kangaroos associated with their watermelons. What we don't know for sure is whether or not however, hippopotamus have begun to rent kittens over the past few months, specifically for scorpions associated with their kumquats. However, goldfishes have begun to rent kiwis over the past few months, specifically for bananas associated with their lemons. However, snails have begun to rent plums over the past few months, specifically for grapefruits associated with their grapes.

In modern times however, sheeps have begun to rent cheetahs over the past few months, specifically for spiders associated with their giraffes. However, lions have begun to rent puppies over the past few months, specifically for lions associated with their dolphins. However, prunes have begun to rent apricots over the past few months, specifically for rats associated with their cranberries. By the wayhowever, camels have begun to rent flies over the past few months, specifically for raspberries associated with their cranberries.

Programmatic Control

const expandable = document.querySelector('a-expandable');

// Open the expandable
expandable.open();

// Close the expandable
expandable.close();

// Toggle the state
expandable.toggle();

// Check current state
if (expandable.opened) {
  console.log('Currently expanded');
}

Listening for Changes

const expandable = document.querySelector('a-expandable');

expandable.addEventListener('change', (event) => {
  console.log('Expanded:', event.target.opened);
});

Styling

The expandable uses CSS Grid for smooth height animations. Customise timing with CSS custom properties:

a-expandable {
  --transition-speed: 0.33s;
  --animation-easing: ease;
}

/* Faster animation */
a-expandable.fast {
  --transition-speed: 0.15s;
}

/* Slower, more dramatic */
a-expandable.slow {
  --transition-speed: 0.5s;
  --animation-easing: cubic-bezier(0.4, 0, 0.2, 1);
}

Styling the Toggle

a-expandable [slot="toggle"] {
  cursor: pointer;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

/* Rotate icon when opened */
a-expandable[opened] [slot="toggle"] .icon {
  transform: rotate(180deg);
}

Accessibility

  • ARIA Attributes: Automatically sets aria-expanded on the toggle and aria-labelledby on the content region.
  • Keyboard Support: Toggle responds to Enter and Space keys when focused.
  • Focus Management: Focusable elements inside collapsed content are removed from tab order.
  • Anchor Links: When a URL hash matches an element inside the expandable, it automatically opens to reveal the content.
  • Scroll Into View: When opened or closed, the expandable scrolls into view to prevent content from shifting off-screen.
  • Hidden Until Found: Uses hidden="until-found" for browser find-in-page support (where available).

CSS Custom Properties

PropertyDefaultDescription
--transition-speed0.33sDuration of the expand/collapse animation
--animation-easingeaseEasing function for the animation

Expandable

A element that can collapse and expand its content with an animation.

Example

<a-expandable opened class="accordion">
   <button slot="toggle" type="button">
     <div class="headline">Title</div>
   </button>

   <div>Content</div>
 </a-expandable>

Attributes

Name Type Default value Description
direction undefined undefined

What direction to open
opened undefined undefined

Wether the eleemnt is open or not

Events

Name Description
change

Emitted when the element open state changes

Methods

Expandable.close()

src/Expandable.ts:100

Expandable.open()

src/Expandable.ts:105

Expandable.toggle()

src/Expandable.ts:110

References