@data-slot/collapsible

Headless collapsible (show/hide) component for vanilla JavaScript. Accessible, unstyled, tiny.

Installation

npm install @data-slot/collapsible

Quick Start

<div data-slot="collapsible">
  <button data-slot="collapsible-trigger">Toggle Content</button>
  <div data-slot="collapsible-content" hidden>
    Hidden content revealed on click.
  </div>
</div>

<script type="module">
  import { create } from "@data-slot/collapsible";
  
  const controllers = create();
</script>

API

create(scope?)

Auto-discover and bind all collapsible instances in a scope (defaults to document).

import { create } from "@data-slot/collapsible";

const controllers = create(); // Returns CollapsibleController[]

createCollapsible(root, options?)

Create a controller for a specific element.

import { createCollapsible } from "@data-slot/collapsible";

const collapsible = createCollapsible(element, {
  defaultOpen: false,
  hiddenUntilFound: false,
  onOpenChange: (open) => console.log(open),
});

Options

| Option | Type | Default | Description | |--------|------|---------|-------------| | defaultOpen | boolean | false | Initial open state | | hiddenUntilFound | boolean | false | Use hidden="until-found" when closed | | onOpenChange | (open: boolean) => void | undefined | Callback when open state changes (not called on init) |

Data Attributes

Options can also be set via data attributes on the root element. JS options take precedence.

| Attribute | Type | Default | Description | |-----------|------|---------|-------------| | data-default-open | boolean | false | Initial open state | | data-hidden-until-found | boolean | false | Use hidden="until-found" when closed |

Boolean attributes: present or "true" = true, "false" = false, absent = default.

<!-- Start expanded -->
<div data-slot="collapsible" data-default-open>
  ...
</div>

Controller

| Method/Property | Description | |-----------------|-------------| | open() | Open the collapsible | | close() | Close the collapsible | | toggle() | Toggle the collapsible | | isOpen | Current open state (readonly boolean) | | destroy() | Cleanup all event listeners |

Markup Structure

<div data-slot="collapsible">
  <button data-slot="collapsible-trigger">Toggle</button>
  <div data-slot="collapsible-content">Content</div>
</div>

Both collapsible-trigger and collapsible-content are required.

Styling

Use data-state attributes for CSS styling (available on both root and content):

/* Hidden state */
[data-slot="collapsible-content"][hidden] {
  display: none;
}

/* Or use data-state */
[data-slot="collapsible"][data-state="closed"] [data-slot="collapsible-content"] {
  display: none;
}

/* Animate using data-state on content */
[data-slot="collapsible-content"] {
  overflow: hidden;
  transition: max-height 0.3s;
  max-height: 0;
}

[data-slot="collapsible-content"][data-state="open"] {
  max-height: 500px;
}

/* Presence lifecycle markers */
[data-slot="collapsible-content"][data-starting-style] {
  opacity: 0;
}

[data-slot="collapsible-content"][data-ending-style] {
  opacity: 0;
}

CSS Variables

The content element exposes size variables you can use for dimension animations:

| Variable | Description | |----------|-------------| | --collapsible-panel-height | Panel height (auto at open rest, measured px during transitions, 0px when closed) | | --collapsible-panel-width | Panel width (auto at open rest, measured px during transitions, 0px when closed) |

Example:

[data-slot="collapsible-content"] {
  overflow: hidden;
  height: var(--collapsible-panel-height);
  width: var(--collapsible-panel-width);
  transition: height 0.25s ease, width 0.25s ease, opacity 0.2s ease;
}

[data-slot="collapsible-content"][data-starting-style],
[data-slot="collapsible-content"][data-ending-style] {
  height: 0;
  opacity: 0;
}

Find-in-Page Support

Enable hiddenUntilFound (or data-hidden-until-found) to close panels with hidden="until-found". This allows browser find-in-page to reveal matching text.

With Tailwind:

<div data-slot="collapsible" class="group">
  <button data-slot="collapsible-trigger" class="flex items-center gap-2">
    <span>Show more</span>
    <svg class="group-data-[state=open]:rotate-180 transition-transform">...</svg>
  </button>
  <div data-slot="collapsible-content" class="hidden group-data-[state=open]:block">
    Content here
  </div>
</div>

Accessibility

The component automatically handles:

• aria-expanded state on trigger
• aria-controls linking trigger to content
• role="region" on content
• aria-labelledby linking content back to trigger
• Unique ID generation for trigger and content
• Disabled trigger support (respects disabled attribute and aria-disabled="true")

Events

Outbound Events

Listen for changes via custom events:

element.addEventListener("collapsible:change", (e) => {
  console.log("Collapsible open:", e.detail.open);
});

Inbound Events

Control the collapsible via events:

| Event | Detail | Description | |-------|--------|-------------| | collapsible:set | { open: boolean } | Set open state programmatically |

// Open the collapsible
element.dispatchEvent(
  new CustomEvent("collapsible:set", { detail: { open: true } })
);

// Close the collapsible
element.dispatchEvent(
  new CustomEvent("collapsible:set", { detail: { open: false } })
);

Note: Blocked when trigger is disabled (has disabled attribute or aria-disabled="true").

Deprecated Shapes

The following shape is deprecated and will be removed in v1.0:

// Deprecated: { value: boolean }
element.dispatchEvent(
  new CustomEvent("collapsible:set", { detail: { value: true } })
);

Use { open: boolean } instead.

License

MIT