Building an Accessible Collapsible Element
November 10, 2018

When it comes to JavaScript-based interactions, an accessible user experience is not a given. Even simple interactions require a certain structure.

Enter ARIA

For those new to developing with accessibility in mind, aria- attributes are used to add additional descriptive information regarding the current state of a component, particularly components that change dynamically based on user interaction.

Using the aria-expanded Attribute

aria-expanded informs screen readers that an element is expandable and/or collapsible. Though this is often conveyed visually, if aria-expanded does not describe the change on the page, then the change is not communicated at all to users who cannot see said change.

Here is a simple HTML example of an accordion in the collapsed state:

<div class='accordion'>
  <button aria-expanded='false' class='accordion__button'>
    Example Accordion Button
  </button>

  <div class='accordion__content' style='display: none;'>
    <p>Here is some initially hidden content.</p>
  </div>
</div>

And another example, this time in the expanded state:

<div class='accordion'>
  <button aria-expanded='true' class='accordion__button'>
    Example Accordion Button
  </button>

  <div class='accordion__content' style='display: block;'>
    <p>Here is some initially hidden content.</p>
  </div>
</div>

Using the aria-controls Attribute

aria-controls can be used in conjunction with aria-expanded to properly associate the content of the expanding and collapsing element with the triggering button element. aria-controls must have a value that matches the id of the controlled element. Remember it is critical that every ID on a page is unique!

<div class='accordion'>
  <button aria-expanded='false' class='accordion__button' aria-controls='example-id'>
    Example Accordion Button
  </button>

  <div class='accordion__content' style='display: none;' id='example-id'>
    <p>Here is some initially hidden content.</p>
  </div>
</div>

Working Examples

Conclusion

When building stateful components, its important to ensure that these states are adequately perceivable for all users. In fact, in order to meet the standards set out by the Web Content Accessibility Guidelines (WCAG), all page behavior and content must first be perceivable to all users.

Nick Lemmon
About Me

I'm a frontend developer in Durham, North Carolina who also happens to have an MSW. I'm also a certified Web Accessibility Specialist!

I'm driven to design and build accessible design systems with a great underlying developer experience in mind.

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