Source

File: wp-includes/link-template.php

function get_the_posts_navigation( $args = array() ) {
	$navigation = '';

	// Don't print empty markup if there's only one page.
	if ( $GLOBALS['wp_query']->max_num_pages > 1 ) {
		// Make sure the nav element has an aria-label attribute: fallback to the screen reader text.
		if ( ! empty( $args['screen_reader_text'] ) && empty( $args['aria_label'] ) ) {
			$args['aria_label'] = $args['screen_reader_text'];
		}

		$args = wp_parse_args(
			$args,
			array(
				'prev_text'          => __( 'Older posts' ),
				'next_text'          => __( 'Newer posts' ),
				'screen_reader_text' => __( 'Posts navigation' ),
				'aria_label'         => __( 'Posts' ),
				'class'              => 'posts-navigation',
			)
		);

		$next_link = get_previous_posts_link( $args['next_text'] );
		$prev_link = get_next_posts_link( $args['prev_text'] );

		if ( $prev_link ) {
			$navigation .= '<div class="nav-previous">' . $prev_link . '</div>';
		}

		if ( $next_link ) {
			$navigation .= '<div class="nav-next">' . $next_link . '</div>';
		}

		$navigation = _navigation_markup( $navigation, $args['class'], $args['screen_reader_text'], $args['aria_label'] );
	}

	return $navigation;
}