No Shopping cart is created equal

gistfile1.txt

<script>
//=======================================================
//
// More Awesome scripts and tricks about shopify on www.connectdots.co
//=======================================================

// IMPORTANT: Change this value to whatever the ID of your
// GTM container is.
const GTM_CONTAINER_ID = 'GTM-XXXXXXX';

//=======================================================
// Only customise the below if you know what you're doing
//=======================================================

// Initialise data layer object

var dataLayer = [{
page: {
type: '{{ template }}',
currency:'{{shop.currency}}',
title: '{{ page_title }}'
},
}];

{% if template contains 'product' %}
//=======================================================
// Product pages
//=======================================================
dataLayer[0].page.breadcrumb = '{{ collection.title }}';
dataLayer[0].ecommerce = {
'detail': {
'actionField': {'list':'{{collection.title}}'},
'products': [{
'name': '{{ product.title }}',
'id': '{{ product.id }}',
'price': ({{ product.price }} / 100).toString(),
'brand': '{{ product.vendor }}',
'category': '{{ product.type }}'
}]
}
};

  {% elsif template contains 'cart' %}
    //=======================================================
    // Cart page
    //=======================================================
    var items = []
    {% for line_item in cart.items %}
        item = {};
        item.id = '{{line_item.product_id}}';
        item.name = '{{line_item.product.title}}';
        item.category = '{{line_item.product.type}}';
        item.price = {{line_item.line_price | times: 0.01}};
        item.quantity = {{line_item.quantity | default: 0}};
        items.push(item);
    {% endfor %}
        var contents = []
    {% for line_item in cart.items %}
        content = {};
        content.id = '{{line_item.product_id}}';
        content.price = {{line_item.line_price | times: 0.01}};
        content.quantity = {{line_item.quantity | default: 0}};
        contents.push(content);
    {% endfor %}
    dataLayer.push({
     'event': 'Viewed Shopping Cart',
     'items' : '{{ cart.item_count }}',
     'cartPrice' : '{{ cart.total_price | times: 0.01}}',
     'currency': "{{shop.currency}}",
     'product': items,
      'content': contents
    });
  
{% endif %}

//=======================================================
// GTM container tag
//=======================================================
<!-- Google Tag Manager -->
(function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':
new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],
j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src=
'https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);
})(window,document,'script','dataLayer', GTM_CONTAINER_ID);
<!-- End Google Tag Manager -->
</script>