WordPress: How to check if you're on the login/register page

login_page_check.php

<?php
// Both login and register page
if ( isset( $GLOBALS[ 'pagenow' ] ) && ( false === in_array( $GLOBALS[ 'pagenow' ], array( 'wp-login.php', 'wp-register.php' ) ) ) ) {
	// Do something
}

// Login page only
if ( isset( $GLOBALS[ 'pagenow' ] ) && ( false === in_array( $GLOBALS[ 'pagenow' ], array( 'wp-login.php' ) ) ) ) {
	// Do something
}

// Register page only
if ( isset( $GLOBALS[ 'pagenow' ] ) && ( false === in_array( $GLOBALS[ 'pagenow' ], array( 'wp-register.php' ) ) ) ) {
	// Do something
}