WordPress at a glance
function is not described

WP_Query::is_author() public WP 3.1.0

Is the query for an existing author archive page?

If the $author parameter is specified, this function will additionally check if the query is for one of the authors specified.

{} It's a method of the class: WP_Query{}

No Hooks.

Return

true/false. Whether the query is for an existing author archive page.

Usage

global $wp_query;
$wp_query->is_author( $author );
$author(int/string/int[]/string[])
User ID, nickname, nicename, or array of such to check against.
Default: ''

Changelog

Since 3.1.0 Introduced.

Code of WP_Query::is_author() WP 5.5.3

<?php
public function is_author( $author = '' ) {
	if ( ! $this->is_author ) {
		return false;
	}

	if ( empty( $author ) ) {
		return true;
	}

	$author_obj = $this->get_queried_object();

	$author = array_map( 'strval', (array) $author );

	if ( in_array( (string) $author_obj->ID, $author, true ) ) {
		return true;
	} elseif ( in_array( $author_obj->nickname, $author, true ) ) {
		return true;
	} elseif ( in_array( $author_obj->user_nicename, $author, true ) ) {
		return true;
	}

	return false;
}