Bootstrap 右侧的 4（Bootswatch）上的多级导航栏

Question

所以我在 Bootswatch 4 中有一个多级导航栏 (Bootstrap 4) 在桌面版的右侧（我从一个例子中得到的，但没有真正理解 CSS 和 Javascript 在它后面）并且我想像通常使用 "dropdown-menu-right" 一样将打开的子菜单弹出到左侧，这在这里没有帮助。我怎样才能让子菜单弹出到左边？谁能帮我看看 CSS / Javascript 是如何工作的？

<!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>

Answer 1

您需要调整子菜单的left位置...

.dropdown-submenu>.dropdown-menu {
    top: 0;
    left: -10rem; /* 10rem is the min-width of dropdown-menu */
    position: relative;
}

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