Source

File: wp-includes/post-template.php

function the_title_attribute( $args = '' ) {
	$defaults    = array(
		'before' => '',
		'after'  => '',
		'echo'   => true,
		'post'   => get_post(),
	);
	$parsed_args = wp_parse_args( $args, $defaults );

	$title = get_the_title( $parsed_args['post'] );

	if ( strlen( $title ) == 0 ) {
		return;
	}

	$title = $parsed_args['before'] . $title . $parsed_args['after'];
	$title = esc_attr( strip_tags( $title ) );

	if ( $parsed_args['echo'] ) {
		echo $title;
	} else {
		return $title;
	}
}