function hs_post_classes( $classes, $class, $post_id ) {
if( is_single() ) {
$classes[] .= 'hs-single-post';
} else if ( is_page() ) {
$classes[] .= 'hs-page';
} else {
$classes[] .= 'main-post';
}
return $classes;
}
add_filter( 'post_class', 'hs_post_classes', 10, 3 );