//get_queried_object_id
if ( is_category() ) {
$catid = get_queried_object_id();
} elseif ( is_single() ) {
$cats = wp_get_post_terms( get_queried_object_id(), 'category', array( 'fields' => 'ids' ) ); // category object
$catid = $cats[0];
}
//ref: https://wordpress.stackexchange.com/users/31545/pieter-goosen
Boucler en dehors de la boucle