二级菜单js

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>二级菜单示例</title>
    <style>
        ul {
            list-style-type: none;
            padding: 0;
        }
        .menu {
            width: 200px;
        }
        .submenu {
            display: none;
            padding-left: 20px;
        }
        .menu li:hover > .submenu {
            display: block;
        }
    </style>
</head>
<body>
    <ul class="menu">
        <li>主菜单项1
            <ul class="submenu">
                <li>子菜单项1.1</li>
                <li>子菜单项1.2</li>
            </ul>
        </li>
        <li>主菜单项2
            <ul class="submenu">
                <li>子菜单项2.1</li>
                <li>子菜单项2.2</li>
            </ul>
        </li>
    </ul>

    <script>
        document.querySelectorAll('.menu > li').forEach(item => {
            item.addEventListener('mouseenter', () => {
                item.querySelector('.submenu').style.display = 'block';
            });
            item.addEventListener('mouseleave', () => {
                item.querySelector('.submenu').style.display = 'none';
            });
        });
    </script>
</body>
</html>