js鼠标经过显示下拉菜单

<div class="dropdown">
  <button class="dropbtn">鼠标经过显示菜单</button>
  <div class="dropdown-content" id="dropdownMenu">
    <a href="#">链接1</a>
    <a href="#">链接2</a>
    <a href="#">链接3</a>
  </div>
</div>

.dropdown {
  position: relative;
  display: inline-block;
}

.dropdown-content {
  display: none;
  position: absolute;
  background-color: #f9f9f9;
  min-width: 160px;
  box-shadow: 0px 8px 16px 0px rgba(0,0,0,0.2);
  z-index: 1;
}

.dropdown-content a {
  color: black;
  padding: 12px 16px;
  text-decoration: none;
  display: block;
}

.dropdown-content a:hover {
  background-color: #f1f1f1;
}

.show {
  display: block;
}

document.addEventListener('DOMContentLoaded', function() {
  var dropdownBtn = document.querySelector('.dropbtn');
  var dropdownMenu = document.getElementById('dropdownMenu');

  dropdownBtn.addEventListener('mouseover', function() {
    dropdownMenu.classList.add('show');
  });

  dropdownBtn.addEventListener('mouseout', function() {
    dropdownMenu.classList.remove('show');
  });

  // 防止鼠标从按钮移到菜单时菜单消失
  dropdownMenu.addEventListener('mouseover', function() {
    dropdownMenu.classList.add('show');
  });

  dropdownMenu.addEventListener('mouseout', function() {
    dropdownMenu.classList.remove('show');
  });
});