标题切换未显示，无法展开菜单

document.addEventListener('DOMContentLoaded', function() {
    var menuItems = document.querySelectorAll('.menu-item');

    menuItems.forEach(function(item) {
        item.addEventListener('click', function() {
            var subMenu = this.querySelector('.sub-menu');
            if (subMenu) {
                subMenu.style.display = subMenu.style.display === 'block' ? 'none' : 'block';
            }
        });
    });
});

.menu-item {
    cursor: pointer;
}

.sub-menu {
    display: none;
}

<div class="menu-item">
    <span>菜单项</span>
    <div class="sub-menu">
        <div>子菜单项1</div>
        <div>子菜单项2</div>
    </div>
</div>