Does anyone know why I can't hide a dropdown using this code?

window.addEventListener('scroll', function() {
            // close any open dropdowns
            $('.dropdown-menu.show').each(function() {
                var dropdown = $(this).closest('.dropdown')[0];
                mdb.Dropdown.getInstance(dropdown).hide();
                //$(this).removeClass('show');
            });
        });

The console shows an error: Uncaught TypeError: Cannot read properties of null (reading 'hide'). I wish I knew the jQuery way to hide a dropdown but can't see any docs showing how to control them via jQuery. Can anyone help? I can close the drop down's via getting rid of the show class but I would rather do it via the API so it fades out. Thanks!