enqueue and localizing the Javascript.

//enqueue and localizing the Javascript.

function assets() {
    wp_enqueue_script('ajax_filter_post_mdu', get_template_directory_uri() . '/js/ajax-filter-posts.js', ['jquery'], null, true);
    wp_localize_script( 'ajax_filter_post_mdu', 'bobz', array(
        'nonce'    => wp_create_nonce( 'bobz' ),
        'ajax_url' => admin_url( 'admin-ajax.php' )
    ));
}
add_action('wp_enqueue_scripts', 'assets', 100);