如何创建响应式下拉菜单

<nav>
  <ul>
    <li><a href="#">菜单项1</a></li>
    <li><a href="#">菜单项2</a></li>
    <li><a href="#">菜单项3</a></li>
  </ul>
</nav>

nav {
  background-color: #f1f1f1;
}

nav ul {
  list-style-type: none;
  margin: 0;
  padding: 0;
}

nav li {
  display: inline-block;
}

nav a {
  display: block;
  padding: 10px;
  text-decoration: none;
  color: #333;
}

/* 媒体查询 */
@media screen and (max-width: 600px) {
  nav ul {
    display: none;
  }
  
  nav li {
    display: block;
  }
}

var menuToggle = document.querySelector('.menu-toggle');
var menuItems = document.querySelector('nav ul');

menuToggle.addEventListener('click', function() {
  menuItems.classList.toggle('show');
});