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Last updated: May 5, 2024, 6:53 p.m.

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<h1>Navigation Links: Disclosure Pattern</h1>
      <div class="disclosure-button-links">
        <button type="button"
          aria-expanded="false"
          aria-controls="id-container">
          WAI-ARIA Quick Links
          <svg xmlns="http://www.w3.org/2000/svg"
               class="down"
               width="12"
               height="9"
               viewBox="0 0 12 9">
            <polygon points="1 0, 11 0, 6 8"></polygon>
          </svg>
        </button>
        <ul id="id-container" class="menu">
          <li>
            <a href="https://www.w3.org/">
              W3C Home Page
            </a>
          </li>
          <li>
            <a href="https://www.w3.org/standards/webdesign/accessibility">
              W3C Web Accessibility Initiative
            </a>
          </li>
          <li>
            <a href="https://www.w3.org/TR/wai-aria/">
              ARIA Specification
            </a>
          </li>
          <li>
            <a href="https://w3c.github.io/aria-practices/">
              Authoring Practices
            </a>
          </li>
          <li>
            <a href="https://www.w3.org/TR/html-aria/#el-li">
              HTML Accessibility API Mappings
            </a>
          </li>
          <li>
            <a href="https://w3c.github.io/core-aam/#mapping_role">
              Core ARIA Accessibility API Mappings
            </a>
          </li>
          <li>
            <a href="https://www.w3.org/TR/accname-aam-1.1/">
              Accessible Name and Description
            </a>
          </li>
        </ul>
      </div>

<p>More information on the <a href="https://w3c.github.io/aria-practices/#disclosure">ARIA disclosure pattern</a>.</p>

<h2>Keyboard Features</h2>
      <ul>
        <li>Button open and closes the list of links using <kbd>space</kbd> or <kbd>enter</kbd> key.</li>
        <li>Pressing the <kbd>esc</kbd> key when focus is on a link closes the container element and moves focus back to the button..</li>
      </ul>

<h2>ARIA Markup</h2>
      <ul>
        <li><code>aria-expanded="true"</code> on the button when the container is open.</li>
        <li><code>aria-expanded="false"</code> on the button when the container is closed.</li>
        <li><code>aria-controls="id-container"</code> on the button to reference the <code>id</code> of container element that opens and closes.</li>
      </ul>

<h2>High Contrast Support</h2>
      <ul>
        <li>When <code>button</code> does <em>not</em> have focus, CSS <code>border</code> property is set to <code>1px</code>.</li>
        <li>When <code>button</code> does have focus, CSS <code>border</code> property is set to <code>3px</code> and padding is reduced by <code>2px</code>.</li>
        <li>When <code>a</code> element does <em>not</em> have focus, CSS <code>border</code> property is set to <code>none</code>.</li>
        <li>When <code>a</code> element does have focus, CSS <code>border</code> property is set to <code>2px</code> and padding is reduced by <code>2px</code>.</li>
      </ul>

CSS

.disclosure-button-links {
  margin: 0;
  font-size: 110%;
}

.disclosure-button-links button {
  margin: 0;
  padding: 6px;
  display: inline-block;
  position: relative;
  background-color: #034575;
  border: 1px solid #034575;
  font-size: 0.9em;
  color: white;
  border-radius: 5px;
}

.disclosure-button-links .menu {
  margin: 0;
  padding: 7px 4px;
  list-style: none;
  display: none;
  position: absolute;
  border: 2px solid #034575;
  border-radius: 5px;
  background-color: #eee;
}

.disclosure-button-links .menu a {
  margin: 0;
  padding: 6px;
  display: block;
  width: 24em;
  background-color: #eee;
  border: none;
  color: black;
  border-radius: 5px;
  text-decoration: none;
}

.disclosure-button-links .menu a:hover {
  background-color: #034575;
  color: white;
 }

.disclosure-button-links button svg.down {
  padding-left: 0.125em;
  fill: currentColor;
  stroke: currentColor;
}

.disclosure-button-links button.open svg.down {
  transform: rotate(180deg);
}

/* Focus and hover styling */

.disclosure-button-links button:focus,
.disclosure-button-links button:hover {
  padding: 4px;
  background-color: #dddddd;
  border: 3px solid #034575;
  color: #222222;

}

.disclosure-button-links a:focus,
.disclosure-button-links a:hover {
  padding: 4px;
  background-color: #dddddd;
  border: 2px solid #034575;
  color: #222222;
}

JavaScript

class DisclosureButtonLinks {

constructor(domNode) {

this.domNode       = domNode;
    this.buttonNode    = domNode.querySelector('button');
    this.containerNode = domNode.querySelector('ul');

this.buttonNode.addEventListener('click', this.onButtonClick.bind(this));
    this.buttonNode.addEventListener('blur', this.onBlur.bind(this));

const links = this.containerNode.querySelectorAll('a');
    for (let i = 0; i < links.length; i += 1) {
      links[i].addEventListener('keydown', this.onLinkKeyDown.bind(this));
      links[i].addEventListener('blur', this.onBlur.bind(this));
    }
    window.addEventListener('mousedown', this.onBackgroundMousedown.bind(this), true);
  }

// Container methods

openContainer() {
    this.containerNode.style.display = 'block';
    this.buttonNode.setAttribute('aria-expanded', 'true');
  }

closeContainer() {
    if (this.isOpen()) {
      this.buttonNode.setAttribute('aria-expanded', 'false');
      this.containerNode.style.display = 'none';
    }
  }

isOpen() {
    return this.buttonNode.getAttribute('aria-expanded') === 'true';
  }

onButtonClick(event) {
    if (this.isOpen()) {
      this.closeContainer();
    }
    else {
      this.openContainer();
    }

event.stopPropagation();
    event.preventDefault();
  }

onLinkKeyDown(event) {
    if (event.key === 'Esc' || event.key === 'Escape') {
      this.closeContainer();
      this.buttonNode.focus();
      event.stopPropagation();
      event.preventDefault();
    }
  }

onBlur(event) {
    if (!this.domNode.contains(event.relatedTarget)) {
      if (this.isOpen()) {
        this.closeContainer();
      }
    }
  }

onBackgroundMousedown(event) {
    if (!this.domNode.contains(event.target)) {
      if (this.isOpen()) {
        this.closeContainer();
        this.buttonNode.focus();
      }
    }
  }
}

// Initialize navigation disclosure buttons

window.addEventListener('load', function () {
  const disclosureButtons = document.querySelectorAll('.disclosure-button-links');
  for(let i = 0; i < disclosureButtons.length; i += 1) {
    new DisclosureButtonLinks(disclosureButtons[i]);
  }
});