Function computeAriaExpanded

src/role-helpers.js:302–305

* @param {Element} element - * @returns {boolean | undefined} - false/true if (not)expanded, undefined if not expand-able

(element)

 * @returns {boolean | undefined} - false/true if (not)expanded, undefined if not expand-able
 */
function computeAriaExpanded(element) {
  // https://www.w3.org/TR/wai-aria-1.1/#aria-expanded
  return checkBooleanAttribute(element, 'aria-expanded')
}

function checkBooleanAttribute(element, attribute) {
  const attributeValue = element.getAttribute(attribute)