每当用户单击下拉列表时，刷新下拉列表选项

<!-- HTML -->
<select id="myDropdown">
  <option value="">请选择</option>
</select>

<!-- JavaScript -->
<script>
  const dropdown = document.getElementById('myDropdown');

  dropdown.addEventListener('click', function() {
    // 发送请求获取最新的选项数据
    fetch('/api/options')
      .then(response => response.json())
      .then(data => {
        // 清空下拉列表的选项
        dropdown.innerHTML = '<option value="">请选择</option>';

        // 添加新的选项
        data.forEach(option => {
          const newOption = document.createElement('option');
          newOption.value = option.value;
          newOption.textContent = option.label;
          dropdown.appendChild(newOption);
        });
      })
      .catch(error => {
        console.error('Error:', error);
      });
  });
</script>