Add body class to WordPress posts without featured image

add-body-class-wp-posts-no-featured-image.txt

/**
*
* Add body class to posts without featured image
*
*/

function add_body_class_no_featured_image( $classes ) {
  if(is_single() && !has_post_thumbnail()) {
    $classes[] = 'no-featured-image';
  }
  return $classes;
}
add_filter( 'body_class','add_body_class_no_featured_image' );