如何将aria-expanded设置为html select

<select aria-expanded="true">
  <option value="option1">Option 1</option>
  <option value="option2">Option 2</option>
  <option value="option3">Option 3</option>
</select>

<select id="mySelect" aria-expanded="false" onclick="toggleExpanded()">
  <option value="option1">Option 1</option>
  <option value="option2">Option 2</option>
  <option value="option3">Option 3</option>
</select>

<script>
function toggleExpanded() {
  var selectElement = document.getElementById("mySelect");
  var expanded = selectElement.getAttribute("aria-expanded");
  
  if (expanded === "true") {
    selectElement.setAttribute("aria-expanded", "false");
  } else {
    selectElement.setAttribute("aria-expanded", "true");
  }
}
</script>