https://mnk.org.ua/static/js/vendors/bootstrap-4-navbar.js

1$( document ).ready( function () {
2    $( '.dropdown-menu a.dropdown-toggle' ).on( 'click', function ( e ) {
3        var $el = $( this );
4        var $parent = $( this ).offsetParent( ".dropdown-menu" );
5        if ( !$( this ).next().hasClass( 'show' ) ) {
6            $( this ).parents( '.dropdown-menu' ).first().find( '.show' ).removeClass( "show" );
7        }
8        var $subMenu = $( this ).next( ".dropdown-menu" );
9        $subMenu.toggleClass( 'show' );
10
11        $( this ).parent( "li" ).toggleClass( 'show' );
12
13        $( this ).parents( 'li.nav-item.dropdown.show' ).on( 'hidden.bs.dropdown', function ( e ) {
14            $( '.dropdown-menu .show' ).removeClass( "show" );
15        } );
16
17         if ( !$parent.parent().hasClass( 'navbar-nav' ) ) {
18            $el.next().css( { "top": $el[0].offsetTop, "left": $parent.outerWidth() - 4 } );
19        }
20
21        return false;
22    } );
23} );