如何将第三级添加到这个多级引导下拉列表中

Question

我喜欢这个答案中的多级下拉菜单，但不知道如何向菜单中添加额外的子级别。有人能告诉我怎么做吗？当我添加一个复制此模式的新子菜单类时，它与第二级同时出现：如下所示。

css

.dropdown-submenu{
position: relative;
}
.dropdown-submenu a::after{
transform: rotate(-90deg);
position: absolute;
right: 3px;
top: 40%;
}
.dropdown-submenu:hover .dropdown-menu, .dropdown-submenu:focus .dropdown-menu{
display: flex;
flex-direction: column;
position: absolute !important;
margin-top: -30px;
left: 100%;
}
@media (max-width: 992px) {
.dropdown-menu{
width: 50%;
}
.dropdown-menu .dropdown-submenu{
width: auto;
}
}

html

<nav class="navbar navbar-toggleable-md navbar-light bg-faded">
<button class="navbar-toggler navbar-toggler-right" type="button" data-toggle="collapse" data-target="#navbarNavDropdown" aria-controls="navbarNavDropdown" aria-expanded="false" aria-label="Toggle navigation">
<span class="navbar-toggler-icon"></span>
</button>
<a class="navbar-brand" href="#">Navbar</a>
<div class="collapse navbar-collapse" id="navbarNavDropdown">
<ul class="navbar-nav mr-auto">
<li class="nav-item active">
<a class="nav-link" href="#">Home <span class="sr-only">(current)</span></a>
</li>
<li class="nav-item">
<a class="nav-link" href="#">Link 1</a>
</li>
<li class="nav-item dropdown">
<a class="nav-link dropdown-toggle" href="http://example.com" id="navbarDropdownMenuLink" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
Dropdown link
</a>
<ul class="dropdown-menu" aria-labelledby="navbarDropdownMenuLink">
<li><a class="dropdown-item" href="#">Action</a></li>
<li><a class="dropdown-item" href="#">Another action</a></li>
<li class="dropdown-submenu"><a class="dropdown-item dropdown-toggle" data-toggle="dropdown" href="#">Something else here</a>
<ul class="dropdown-menu">
<a class="dropdown-item" href="#">A</a>
<a class="dropdown-item" href="#">b</a>
</ul>
</li>
</ul>
</li>
</ul>
</div>
</nav>

Answer 1

简单的修复方法，只需将选择器约束为其直接子项，如下所示：

.dropdown-submenu:hover > .dropdown-menu, .dropdown-submenu:focus > .dropdown-menu{
display: flex;
flex-direction: column;
position: absolute !important;
margin-top: -30px;
left: 100%!important;
}

然后你可以这样做：

<a class="btn btn-secondary dropdown-toggle mb-1" href="http://example.com" id="navbarDropdownMenuLink" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
Style
</a>
<ul class="dropdown-menu" aria-labelledby="navbarDropdownMenuLink">
<li><a class="dropdown-item" href="#">Action</a></li>
<li class="dropdown-submenu"><a class="dropdown-item dropdown-toggle" data-toggle="dropdown" href="#">Level 2</a>
<ul class="dropdown-menu">
<a class="dropdown-item" href="#">A</a>
<a class="dropdown-item" href="#">b</a>
<li class="dropdown-submenu"><a class="dropdown-item dropdown-toggle" data-toggle="dropdown" href="#">Level 3</a>
<ul class="dropdown-menu">
<a class="dropdown-item" href="#">c</a>
<a class="dropdown-item" href="#">d</a>
</ul>
</li>
</ul>
</li>
</ul>