如何制作iPhone下拉式按钮

<button id="dropdown-btn">下拉按钮</button>
<ul id="dropdown-menu">
  <li>选项1</li>
  <li>选项2</li>
  <li>选项3</li>
</ul>

#dropdown-btn {
  position: relative;
  display: inline-block;
  background-color: #f1f1f1;
  color: #333;
  padding: 10px;
  border: none;
  cursor: pointer;
}

#dropdown-menu {
  position: absolute;
  display: none;
  background-color: #f1f1f1;
  list-style-type: none;
  padding: 0;
  margin: 0;
  box-shadow: 0 2px 5px rgba(0, 0, 0, 0.2);
}

#dropdown-menu li {
  padding: 10px;
  cursor: pointer;
}

#dropdown-menu li:hover {
  background-color: #ddd;
}

var dropdownBtn = document.getElementById('dropdown-btn');
var dropdownMenu = document.getElementById('dropdown-menu');

dropdownBtn.addEventListener('click', function() {
  if (dropdownMenu.style.display === 'none') {
    dropdownMenu.style.display = 'block';
  } else {
    dropdownMenu.style.display = 'none';
  }
});