A simple way to show navbar submenus on hover in Bootstrap 4
<!DOCTYPE html>
<html >
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Drop Down Sub Menu</title>
<base target="_self">
<meta name="description" content="A simple way to show navbar submenus on hover in Bootstrap 4" />
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css" />
<style type="text/css">.navbar-nav li:hover > ul.dropdown-menu {
display: block;
}
.dropdown-submenu {
position:relative;
}
.dropdown-submenu>.dropdown-menu {
top:0;
left:100%;
margin-top:-6px;
}
/* rotate caret on hover */
.dropdown-menu > li > a:hover:after {
text-decoration: underline;
transform: rotate(-90deg);
}
</style>
</head>
<body >
<nav class="navbar navbar-expand-md navbar-light bg-light">
<a class="navbar-brand pb-2" href="#">Navbar</a>
<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="navbar-nav">
<li class="nav-item active">
<a class="nav-link" href="#">Home <span class="sr-only">(current)</span></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
</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" href="http://google.com">Google</a>
<ul class="dropdown-menu">
<li><a class="dropdown-item" href="#">Submenu</a></li>
<li><a class="dropdown-item" href="#">Submenu0</a></li>
<li class="dropdown-submenu"><a class="dropdown-item dropdown-toggle" href="#">Submenu 1</a>
<ul class="dropdown-menu">
<li><a class="dropdown-item" href="#">Subsubmenu1</a></li>
<li><a class="dropdown-item" href="#">Subsubmenu1</a></li>
</ul>
</li>
<li class="dropdown-submenu"><a class="dropdown-item dropdown-toggle" href="#">Submenu 2</a>
<ul class="dropdown-menu">
<li><a class="dropdown-item" href="#">Subsubmenu2</a></li>
<li><a class="dropdown-item" href="#">Subsubmenu2</a></li>
</ul>
</li>
</ul>
</li>
</ul>
</li>
</ul>
</div>
</nav>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.2.4/jquery.min.js"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/js/bootstrap.min.js"></script>
</body>
</html>
