Shopify Purchase Event Tracking with GTM.js

<script>
/* track the sale in GTM */
$(document).on(`page:load page:change`, function() {
  try {
    
    if (Shopify.checkout && Shopify.Checkout.page == 'thank_you') {
      dataLayer.push({
        'event': 'eec.purchase',
        'ecommerce': {
         'currencyCode': Shopify.checkout.currency,
          'purchase': {
            'actionField': {
              'id': Shopify.checkout.order_id,
              'revenue': Shopify.checkout.total_price,
              'tax': Shopify.checkout.total_tax, 
              'shipping': Shopify.checkout.shipping_rate.price, 
              'coupon': (Shopify.checkout.discount ? Shopify.checkout.discount.code : ''), 
              'discount': (Shopify.checkout.discount ? Shopify.checkout.discount.amount : '') 
            },
            'products': Shopify.checkout.line_items.map(function(item) { 
                            return {
                                    'name': item.title,
                                    'id': item.variant_id,
                                    'price': item.price,
                                    'brand': item.vendor,
                                    'category': '',
                                    'variant': item.variant,
                                    'quantity': item.quantity,
                                    'coupon': ''
                                   };
                          })
          }
        }
      });
    
    }
    
  } catch(err) {
    console.log(err);
  }
});
</script>