Ajax message after node save

Question

I am trying to add a Ajax Alert or popup message inside a hook_node_presave or hook_node_update, but it is not working.

My current code look like this, but I have tried a lot of other ajax

$response = new ajaxResponse();
$response->addCommand(new AlertCommand('Ajax test'));
return $response;

The node is saved but no alert and no errors in the console. Drupal 9