单击按钮显示菜单，再次单击按钮隐藏菜单

<button id="menuButton">菜单</button>
<div id="menuContainer">
  <ul>
    <li>菜单项1</li>
    <li>菜单项2</li>
    <li>菜单项3</li>
  </ul>
</div>

#menuButton {
  background-color: #ccc;
  border: none;
  padding: 10px;
  cursor: pointer;
}

#menuContainer {
  display: none;
  background-color: #f1f1f1;
  padding: 10px;
}

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

#menuContainer li {
  margin-bottom: 5px;
}

var menuButton = document.getElementById("menuButton");
var menuContainer = document.getElementById("menuContainer");

menuButton.addEventListener("click", function() {
  if (menuContainer.style.display === "none") {
    menuContainer.style.display = "block";
  } else {
    menuContainer.style.display = "none";
  }
});