js三级下拉菜单js代码

<nav>
  <ul class="menu">
    <li>
      <a href="#">菜单1</a>
      <ul class="submenu">
        <li>
          <a href="#">子菜单1.1</a>
          <ul class="submenu">
            <li><a href="#">子菜单1.1.1</a></li>
            <li><a href="#">子菜单1.1.2</a></li>
          </ul>
        </li>
        <li><a href="#">子菜单1.2</a></li>
      </ul>
    </li>
    <li>
      <a href="#">菜单2</a>
      <ul class="submenu">
        <li><a href="#">子菜单2.1</a></li>
        <li><a href="#">子菜单2.2</a></li>
      </ul>
    </li>
  </ul>
</nav>

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

nav > ul > li {
  display: inline-block;
  position: relative;
}

nav ul ul {
  display: none;
  position: absolute;
  top: 100%;
  left: 0;
  background-color: #fff;
  box-shadow: 0 2px 5px rgba(0,0,0,0.2);
}

nav ul ul ul {
  top: 0;
  left: 100%;
}

nav li:hover > ul {
  display: block;
}

nav a {
  display: block;
  padding: 10px 20px;
  text-decoration: none;
  color: #333;
}

nav a:hover {
  background-color: #f0f0f0;
}

document.addEventListener('DOMContentLoaded', function() {
  const navItems = document.querySelectorAll('.menu > li');

  navItems.forEach(item => {
    item.addEventListener('mouseenter', function() {
      const submenu = this.querySelector('.submenu');
      if (submenu) {
        submenu.style.display = 'block';
      }
    });

    item.addEventListener('mouseleave', function() {
      const submenu = this.querySelector('.submenu');
      if (submenu) {
        submenu.style.display = 'none';
      }
    });
  });
});