WordPress at a glance
function is not described

_wp_menus_changed() WP 4.9.0

Handle menu config after theme change.

No Hooks.

Return

Nothing (null).

Usage

_wp_menus_changed();

Code of wp menus changed: wp-includes/nav-menu.php VER 5.0.3

<?php
function _wp_menus_changed() {
	$old_nav_menu_locations    = get_option( 'theme_switch_menu_locations', array() );
	$new_nav_menu_locations    = get_nav_menu_locations();
	$mapped_nav_menu_locations = wp_map_nav_menu_locations( $new_nav_menu_locations, $old_nav_menu_locations );

	set_theme_mod( 'nav_menu_locations', $mapped_nav_menu_locations );
	delete_option( 'theme_switch_menu_locations' );
}