Why doesn't $this->view->registerJs() fire from a controller on ajax form submission?

Question

Yii

Submitting a form via pjax. In the controller I write something like:

$this->view->registerJs('console.log("hello world!")');
return $this->renderAjax(/* bla bla bla */);

The response body comes without this javascript. Although in another controller similar code works. CHADNT?