通过单击另一个div打开列表下拉菜单

<div id="button">点击我</div>
<div id="menu">
  <ul>
    <li>菜单项1</li>
    <li>菜单项2</li>
    <li>菜单项3</li>
  </ul>
</div>

#button {
  background-color: #ccc;
  padding: 10px;
  cursor: pointer;
}

#menu {
  display: none;
}

#menu ul {
  list-style: none;
  padding: 0;
}

#menu li {
  padding: 5px;
  background-color: #f1f1f1;
  cursor: pointer;
}

var button = document.getElementById('button');
var menu = document.getElementById('menu');

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