所以我在桌面版右侧sid中的Bootswatch 4（Bootstrap 4）中有一个多级Navbar（我从一个例子中得到的并没有真正理解它背后的CSS和Javascript）并且我想将子菜单打开到左侧通常使用“下拉菜单权限”，这在这里没有帮助。我怎样才能让子菜单向左打开？有人可以帮助我CSS / Javascript看起来像它可以这样工作吗？
<!DOCTYPE html>
<html lang="de-DE">
<head>
<meta charset="utf-8" />
<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootswatch/4.1.0/cosmo/bootstrap.min.css">
<link href="bootstrap-4-navbar.css" rel="stylesheet">
<style>
.dropdown-submenu {
position: relative;
}
.dropdown-submenu a::after {
transform: rotate(0deg);
position: absolute;
right: 6px;
top: .8em;
}
.dropdown-submenu .dropdown-menu {
top: 0;
left: 100%;
margin-left: .1rem;
margin-right: .1rem;
}
</style>
<meta name="viewport" content="width=device-width, initial-scale=1" />
</head>
<nav class="navbar navbar-expand-lg fixed-top bg-dark navbar-dark">
<div class="container">
<button class="navbar-toggler" 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>
<div class="collapse navbar-collapse" id="navbarNavDropdown">
<ul class="nav navbar-nav ml-auto">
<li class="nav-item dropdown">
<a class="nav-link dropdown-toggle" href="#" id="navbarDropdownMenuLink" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">AAA</a>
<ul class="dropdown-menu dropdown-menu-right" aria-labelledby="navbarDropdownMenuLink">
<li class="dropdown-submenu"><a class="dropdown-item dropdown-toggle" href="#">Submenu</a>
<ul class="dropdown-menu">
<li class="dropdown-submenu"><a class="dropdown-item dropdown-toggle" href="#">Subsubmenu</a>
<ul class="dropdown-menu">
<li><a class="dropdown-item" href="#">Subsubmenu action</a></li>
<li><a class="dropdown-item" href="#">Another subsubmenu action</a></li>
</ul>
</li>
<li class="dropdown-submenu"><a class="dropdown-item dropdown-toggle" href="#">Second subsubmenu</a>
<ul class="dropdown-menu">
<li><a class="dropdown-item" href="#">Subsubmenu action</a></li>
<li><a class="dropdown-item" href="#">Another subsubmenu action</a></li>
</ul>
</li>
</ul>
</li>
</ul>
</li>
</ul>
</div>
</div>
</nav>
<script src="https://code.jquery.com/jquery-3.2.1.slim.min.js" integrity="sha384-KJ3o2DKtIkvYIK3UENzmM7KCkRr/rE9/Qpg6aAZGJwFDMVNA/GpGFF93hXpG5KkN" crossorigin="anonymous"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.12.9/umd/popper.min.js" integrity="sha384-ApNbgh9B+Y1QKtv3Rn7W3mgPxhU9K/ScQsAP7hUibX39j7fakFPskvXusvfa0b4Q" crossorigin="anonymous"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/js/bootstrap.min.js" integrity="sha384-JZR6Spejh4U02d8jOt6vLEHfe/JQGiRRSQQxSfFWpi1MquVdAyjUar5+76PVCmYl" crossorigin="anonymous"></script>
<script>
$('.dropdown-menu a.dropdown-toggle').on('click', function(e) {
if (!$(this).next().hasClass('show')) {
$(this).parents('.dropdown-menu').first().find('.show').removeClass("show");
}
var $subMenu = $(this).next(".dropdown-menu");
$subMenu.toggleClass('show');
$(this).parents('li.nav-item.dropdown.show').on('hidden.bs.dropdown', function(e) {
$('.dropdown-submenu .show').removeClass("show");
});
return false;
});
</script>
</body>
</html>你需要调整子菜单的left位置......
.dropdown-submenu>.dropdown-menu {
top: 0;
left: -10rem; /* 10rem is the min-width of dropdown-menu */
position: relative;
}
Bootstrap 4 Dropdown Submenus Right