Add class into the body tag to check if user is login or logout

functions.php

/**
 * Function to add class when user is login in or not login in
 */
function awp_body_class_callback( $classes ) {
  $class = get_current_user_id() ? 'user-login' : 'user-logout';

	return array_merge( $classes, array( $class ) );
}
add_filter( 'body_class', 'awp_body_class_callback', 10, 1 );