Bootstrap Sub-Menus.
<!DOCTYPE html>
<html>
<head>
…
<link rel="stylesheet" href="https://unpkg.com/bootstrap-submenu@3.0.1/dist/css/bootstrap-submenu.css">
…
<script src="https://unpkg.com/bootstrap-submenu@3.0.1/dist/js/bootstrap-submenu.js" defer></script>
</head>
<body>
…
</body>
</html>Enable Bootstrap-submenu via JavaScript:
// For v2 [data-toggle="dropdown"] is required for [data-submenu].
// For v2 .dropdown-submenu > [data-toggle="dropdown"] is forbidden.
$('[data-submenu]').submenupicker();