<aria-collapsible> Web Component

A dependency-free Web Component that generates progressively-enhanced collapsible regions using ARIA States and Properties.

🐳 📖 See <aria-collapsible> in action!

[!NOTE] Prior to v7.0.0, this package exported a class, Collapsible, which offered similar functionality. If that better suits your needs, the legacy package is available on npm.

Getting <aria-collapsible>

You've got several options for adding this Web Component to your project:

• Download a release from GitHub and do it yourself (old school).
• Install using npm: npm install @jgarber/aria-collapsible --save
• Install using Yarn: yarn add @jgarber/aria-collapsible

Usage

First, add this <script> element to your page which defines the <aria-collapsible> Web Component:

<script type="module" src="aria-collapsible.js"></script>

Use the <aria-collapsible> custom element to wrap a control (typically, a <button> element) and one or more associated regions:

<aria-collapsible>
  <button control hidden>Toggle Menu</button>

  <nav region>
    <ul>
      <li><a href="/">Home</a></li>
      <li><a href="/articles">Articles</a></li>
      <li><a href="/photos">Photos</a></li>
      <li><a href="/links">Links</a></li>
      <li><a href="/about">About</a></li>
    </ul>
  </nav>
</aria-collapsible>

With the markup above, the Web Component will associate the control with one or more regions using the aria-controls attribute. For region elements without id attributes, unique values will be generated. Clicking the control element will alternatively show or hide the associate regions by toggling those element's hidden attribute.

[!IMPORTANT] It's recommended that you include the hidden attribute on the control element. This attribute will prevent the control from being displayed until the Web Component initializes and removes the hidden attribute.

[!IMPORTANT] It's recommended that the region element(s) immediately follow the control element in HTML source order. See the Focus and Reading Order section in Disclosure Widgets for additional information.

Styling the control and region elements is entirely up to you. Beyond the semantics of the hidden attribute and browsers' default styling, this Web Component is unstyled out of the box. Use your imagination. Get creative. The sky's the limit!

In addition to the above-mentioned Disclosure Widgets article, the Web Accessibility Initiative's Disclosure (Show/Hide) Pattern page provides additional examples where you may consider using this Web Component.

Optional Attributes

This Web Component supports a single Boolean attribute, open, that behaves similarly to the <details> element's attribute of the same name. The presence of the open attribute will show regions within the Web Component and set the control's aria-expanded attribute value to true.

An instance of <aria-collapsible> may be opened or closed by programatically setting the open attribute or property:

<aria-collapsible open>
  <button control hidden>Toggle</button>

  <div region>
    <p>I'm visible!</p>
  </div>
</aria-collapsible>

<script>
  // Close the Web Component by updating its `open` property.
  document.querySelector("aria-collapsible").open = false;

  // Re-open the Web Component by setting its `open` attribute.
  document.querySelector("aria-collapsible").setAttribute("open", "any-value-here-works");
</script>

[!IMPORTANT] Boolean attributes like open must be removed (either by using removeAttribute or setting the property to false). Because the attribute is a Boolean, open="false" will display the Web Component's region's content.

[!TIP] You might consider manipulating the open property in conjunction with the window.matchMedia's change event.

const component = document.querySelector("aria-collapsible");
const control = component.querySelector("[control]");

window.matchMedia("(width >= 32rem)").addEventListener("change", (event) => {
  component.open = event.matches;
  control.toggleAttribute("hidden", event.matches);
});

The code snippet above was inspired by the article, Why you should use window.matchMedia when checking for window resizes in Javascript.

Events

The <aria-collapsible> Web Component supports a toggle event which is dispatched whenever the component's open property changes. The event is sent after the control element's aria-expanded attributed and associated regions' hidden attributes are updated. This event is provided to authors who wish (or need!) to provide additional behavior or surface information to users based on this Web Component's state.

Acknowledgments

The following resources were used while making this Web Component:

• Disclosure Widgets by Adrian Roselli
• Disclosure (Show/Hide) Pattern by The Web Accessibility Initiative
• Making Web Component properties behave closer to the platform by Thomas Broyer
• Let's create a Web Component from scratch! and The handleEvent() method is the absolute best way to handle events in Web Components by Chris Ferdinandi

License

The <aria-collapsible> Web Component is freely available under the MIT License.