How to execute javascript code and pass to it some values after an event is triggered?

Question

I'm trying to execute some javascript code and pass to it some values after an event (e.g. Add to Cart event) is triggered. To be more specific I'd like to pass:

• All logged customer details (Firstname, Lastname, Email, etc.)
• Cart details (Product ID, Product Name, amount, price, etc.)

In order to do that, I create my own module like this:

Vendor/Module/registration.php

<?php
\Magento\Framework\Component\ComponentRegistrar::register(
    \Magento\Framework\Component\ComponentRegistrar::MODULE,
    'Vendor_Module',
    DIR
);

Vendor/Module/etc/module.xml

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Module/etc/module.xsd">
    <module name="Vendor_Module" setup_version="1.0.0.0" active="true" />
</config>

Vendor/Module/etc/events.xml

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Event/etc/events.xsd">
   <event name="checkout_cart_save_after"> 
      <observer name="checkout_cart_save_after" instance="Vendor\Module\Observer\AddToCart" /> 
   </event>
</config>

...and here I don't know how to move forward...

Vendor/Module/Observer/AddToCart.php

<?php
namespace Vendor\Module\Observer;

use Magento\Framework\Event\ObserverInterface;
use Magento\Framework\App\RequestInterface;

class AddToCart implements ObserverInterface
{
    public function execute(\Magento\Framework\Event\Observer $observer) {

    }

}

I think I should get cart and customer details in some way, then pass them to a view (E.g. Vendor/Module/view/frontend/templates/add_to_cart.pthml) and execute inside it my Javascript code. Am I wrong? How should I proceed?