Please see comments for more up to date implementations!!

Shopify Checkout Script

<script type="text/javascript">
    !function(){var analytics=window.analytics=window.analytics||[];if(!analytics.initialize)if(analytics.invoked)window.console&&console.error&&console.error("Segment snippet included twice.");else{analytics.invoked=!0;analytics.methods=["trackSubmit","trackClick","trackLink","trackForm","pageview","identify","group","track","ready","alias","page","once","off","on"];analytics.factory=function(t){return function(){var e=Array.prototype.slice.call(arguments);e.unshift(t);analytics.push(e);return analytics}};for(var t=0;t<analytics.methods.length;t++){var e=analytics.methods[t];analytics[e]=analytics.factory(e)}analytics.load=function(t){var e=document.createElement("script");e.type="text/javascript";e.async=!0;e.src=("https:"===document.location.protocol?"https://":"http://")+"cdn.segment.com/analytics.js/v1/"+t+"/analytics.min.js";var n=document.getElementsByTagName("script")[0];n.parentNode.insertBefore(e,n)};analytics.SNIPPET_VERSION="3.0.1";


        window.analytics.load("");

        // identify the customer if they have an account
        {% if customer.id %}
        window.analytics.identify("{{customer.id}}", {
            name: "{{ customer.name }}",
            firstName: "{{ customer.first_name }}",
            lastName: "{{ customer.last_name }}",
            email: "{{ customer.email }}",
            phone: "{{ customer.default_address.phone }}",
            address: {  // uses the default address
                street: "{{ customer.default_address.street }}",
                city: "{{ customer.default_address.city }}",
                state: "{{ customer.default_address.province }}",
                stateCode: "{{ billing_address.province_code }}",
                postalCode: "{{ customer.default_address.zip }}",
                country: "{{ customer.default_address.country }}",
                countryCode: "{{ customer.default_address.country_code }}"
            },
            totalSpent: "{{ customer.total_spent }}",
            allOrdersCount: "{{ customer.orders_count }}",
            allOrderIds: [{% for order in customer.orders %}"{{ order.id }}",{% endfor %}],
        tags: ["{{ customer.tags | join: '", "' }}"]
    });
        {% endif %}
        window.analytics.page('Checkout Page');
    }}();

    // calculate totalDiscount for Completed Order Event
    var discounts = "{{ order.discounts | json }}"
    var totalDiscount = 0;

    for (var i = 0; i< discounts.length; i++ ) {
        totalDiscount += discounts[i].savings;
    }

    analytics.track('Completed Order', {
        orderId: "{{ order_number }}",
        total: "{{ total_price | money_without_currency }}",
        revenue: "{{subtotal_price | money_without_currency }}",
        shipping: "{{shipping_price | money_without_currency }}",
        tax: "{{tax_price | money_without_currency }}",
        discount: totalDiscount,
        products: [
        {% for line_item in line_items %}
    {
        id: "{{ line_item.product_id }}",
                sku: "{{ line_item.sku }}",
            name: "{{ line_item.title }}",
            price: "{{ line_item.price }}",
            quantity: "{{ line_item.quantity }}"
    }
    {% endfor %} ]
    });
</script>

Thanks for the integration code!

I'm currently using this as a part of segment/shopify integration, and i'm seeing an error.

I'm not sure when Shopify made made this change, but order.discounts can't be converted into a json string. As a result from line 34, I get something like "object cannot be filtered to json"

This essentially breaks any additional scripts on the order confirmation page. I found this out when I noticed a discrepancy from the data that segment is passing to Google Analytics, and that orders which had a discount code wouldn't appear.

I recommend using the liquid object discounts_amount see documentation here

For line 47, I'm currently using this instead: discount: {{ discounts_amount | money_without_currency}},

Thanks for this and the comment by @JimmyCouch! I've just gone through and added Segment to my store and found a number of bugs in the existing documented solutions, so have updated them some here:

https://gist.github.com/litch/568bc224ddb28507f90ea7081c5776fd