search term highlighting elasticpress

gistfile1.txt

add_filter(
	'ep_formatted_args',
	function( $formatted_args ) {
		if ( ! empty( $_GET['s'] ) ) {
			foreach ( [ 'post_title', 'post_excerpt', 'author_name', 'terms.post_tag.name', 'terms.category.name' ] as $field ) {
				$formatted_args['highlight']['fields'][ $field ] = [
					'pre_tags'  => [ '<strong style="background:yellow">' ],
					'post_tags' => [ '</strong>' ],
					'type'      => 'plain',
				];
			}
		}
		return $formatted_args;
	}
);

this will add highlight results in the elasticsearch response "highlight": { "post_title": [ "<strong style="background:yellow">Hello</strong> world!" ] }