function new_nav_menu_items($items) {
    $items = "";
    $args = array(
        "post_type" => "page",
        "order"     => "ASC",
        "orderby"   => "menu_order"
    );
    $the_query = new WP_Query($args);

    if($the_query->have_posts()):
        while($the_query->have_posts()):
            $the_query->the_post();
                $items .= '<li><a href="#post-'. get_the_ID() .'">' . get_the_title() . '</a></li>';
        endwhile;
    else:
        echo "";
    endif;

    return $items;
}

add_filter("wp_nav_menu_items", "new_nav_menu_items");

function new_nav_menu_items( $items, $args ) {
    if ( $args->menu == 'primary' ) {
        $items = "";
        $args = array(
            "post_type" => "page",
            "order"     => "ASC",
            "orderby"   => "menu_order"
        );
        $the_query = new WP_Query( $args );
        if ( $the_query->have_posts() ):
            while( $the_query->have_posts() ):
                $the_query->the_post();
                $items .= '<li><a href="#post-' . get_the_ID() . '">' .
                    get_the_title() . '</a></li>';
            endwhile;
        else:
            echo "";
        endif;
    }
    return $items;
}
add_filter( "wp_nav_menu_items", "new_nav_menu_items" );