Remove all nav menu classes ( but keep useful ones… )

I’m trying to remove all menu-item classes (except for .current-menu-{item/parent/ancestor} and .menu-item-has-children)

function custom_nav_menu_css_class($classes) {
    $classes = preg_replace('/^((menu|page)[-_\w+]+)+/', '', $classes);
    return $classes;
}
add_filter('nav_menu_css_class', 'custom_nav_menu_css_class');

This almost does the job, except it removes .menu-item-has-children? Any idea what I should change, to exclude it from being removed?

(P.S. I’d rather not use a custom walker…)

You could work with a white-list and replace the regular expression with something more readable:

add_filter( 'nav_menu_css_class', function( $classes ) {

    $allowed = [
        'menu-item-has-children',
        'current-menu-item'
    ];

    return array_intersect( $classes, $allowed );
});

That would make it easier to maintain the white-list too.