Add JS to head in Cart

Question

I have problem when I want to put JS into head when PHP condition is met, but I'm getting Mage_Core_Exception: Invalid block type excetion no idea why. I have read all the possible issues I have found but looks like there is ton of places I could go wrong and right now Im out of ideas.

I have config.xml where is my module declared. This is only part of it as rest of module is working, also JS and CSS I have in module_name.xml is working properly.

</frontend>
    <layout>
        <updates>
            <module_name>
                <file>module_name.xml</file>
            </module_name>
        </updates>
    </layout>
</frontend>

Then I have module_name.xml I understand that I say here "on checkout/cart page load this template/modulename/prependca.phtml into of page.

<checkout_cart_index translate="label">
    <reference name="head">
        <block type="namespace_moduleName/cart" name="prependca" template="modulename/prependca.phtml"/>
    </reference>
</checkout_cart_index>

Last, but not least, I have this Class of mine:

class Namespace_ModuleName_Block_Cart extends Mage_Checkout_Block_Cart_Abstract {

    public function prependCa() {
        $_quote = Mage::getSingleton('checkout/session')->getQuote();
        if (get_class($_quote) == Mage_Sales_Model_Quote) {
            $head = $this->getLayout()->getBlock('head');
            $head->addJs('namespace/modulenameTotals.js');
            $head->addItem('js', 'namespace/modulenameTotals.js');
        }
    }
}

From what I have read, I did all I had to do, however I still don't get results and only respond I get is Mage_Core_Exception: Invalid block type

Answer 1

1. Go to app/design/frontend/{package}/{theme}/layout/local.xml then add this :

   <checkout_cart_index>
       <reference name="head">
           <action method="addItem"><type>skin_js</type><name>js/my-custom.js</name></action>
       </reference>
   </checkout_cart_index>
   

2. Create your new js file in: skin/frontend/{package}/{theme}/js/my-custom.js then put your code inside.

3. Now your js file will be just loaded in checkout/cart. Don't forget to clear the cache.

---

NB: I see some errors in your code:

1)

<frontend> // not </frontend>
    <layout>
        <updates>
            <module_name>
                <file>module_name.xml</file>
            </module_name>
        </updates>
    </layout>
</frontend>

2)

You can't load this type of block in a head ! but you can do it content, root etc...

If you need is to add a js file, follow my solution.