如何在下拉菜单中添加按钮？

<select>
  <option value="option1">选项1</option>
  <option value="option2">选项2</option>
  <option value="option3">选项3</option>
  <option value="button">按钮</option>
</select>

select option[value="button"] {
  background-color: #4CAF50;
  color: white;
  font-weight: bold;
  border: none;
  cursor: pointer;
}

var dropdown = document.querySelector('select');
dropdown.addEventListener('change', function() {
  if (this.value === 'button') {
    // 执行按钮点击后的操作
    alert('按钮被点击了！');
  }
});