[@robin-w Moderator 5 years, 6 months ago]

you add action is right, and I’d have this as the function (not tested!)

function forum_user_is_spectator(){
if ( is_bbpress() && is_user_logged_in() ) {
   $User_ID = get_current_user_id() ;
	$Spectator = (!empty(current_user_can( 'spectate' )) ? 1  : 0) ;
    if ($Spectator){
       wp_enqueue_script( 'spectator-js', get_template_directory_uri() . '/js/spectator.js', array(), false, true);
       }
    }
}