如何通过点击来显示/隐藏下拉菜单？

<button id="dropdown-btn">点击显示/隐藏下拉菜单</button>
<ul id="dropdown-menu">
  <li>菜单项1</li>
  <li>菜单项2</li>
  <li>菜单项3</li>
</ul>

#dropdown-menu {
  display: none; /* 初始状态下隐藏下拉菜单 */
}

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"; // 点击按钮显示下拉菜单
  } else {
    dropdownMenu.style.display = "none"; // 点击按钮隐藏下拉菜单
  }
});