As a Shopify theme gets more fully featured, it is likely that large amounts of JavaScript are being used to improve and expand the user experience. Making theme changes gets more nerve wracking as the amount of code increases. Did my sales go down because I broke something with the last JavaScript change?

If you’re worried about that next theme publish, it’s time to start monitoring user experiences for JavaScript errors. TrackJS makes error monitoring quick and easy to do!

How To Monitor JavaScript Errors In A Live Shopify Store

TrackJS is purpose built to monitor errors in production websites. It works with virtually every framework out there and Shopify’s theme system is no exception. This example starts with Shopify’s built-in “Dawn” theme and modifies it to include JavaScript error monitoring. That’s overkill for a simple theme built by Shopify, but the concepts should apply to your custom theme as well.

Installing the TrackJS agent is the only step needed to start tracking errors:

1. Get Agent Install Snippet

Copy the “global” agent install snippet from your TrackJS Dashboard’s install page. If using TrackJS Applications, get the application’s snippet from the application management page.

Agent install snippet from the TrackJS Dashboard
Agent install snippet from the TrackJS Dashboard

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2. Insert Snippet In Theme Layout (Install The TrackJS Agent)

The install snippet needs to be present on all of the store’s pages where JavaScript is run. If most pages contain JavaScript, a commonly used layout is a great place to start. For example, the Dawn theme has a layout found at Layout/theme.liquid which used almost everywhere.

The snippet can be inserted using the Shopify Admin site. In the admin site, navigate to “Online Store -> Themes”, click the current theme’s “…” button and click “Edit Code”.

Add the install snippet to the layout and save:

'Layout/theme.liquid' with TrackJS install snippet
'Layout/theme.liquid' with TrackJS install snippet

3. Verify The Install

If your store is not live, test the install by manually sending a JavaScript error. Insert the test code into the same layout, just after the install snippet.

    console.log("Testing TrackJS Install");
    TrackJS.track('Testing TrackJS in my Shopify theme!');
Send a JavaScript error on every page load

The test error will show up in the TrackJS Dashboard if everything is configured correctly:

Test error shown in the TrackJS Dashboard
Test error shown in the TrackJS Dashboard

Don't Forget! Remove this test code when finished.

Know When Customers Hit Missing Urls

The store now has a basic TrackJS setup that captures all JavaScript errors! But we can do more. Why not keep track of any time a customer lands on a missing page? This can be very important in cases where an important affiliate is still using an old product URL.

1. Modify The Main 404 Template or Section

In the Dawn theme, the content for 404 (Not Found) pages is contained in Sections/main-404.liquid. Most themes should have a similar liquid template. Scripts in this template will run any time a user lands on a missing page:

... existing template here ...

  window.TrackJS && TrackJS.track("Page not found: " + window.location);
Track missing pages in 'Sections/main-404.liquid'

2. Test A Missing URL

We can easily modify the address in the browser to test:

Shopify page not found
Shopify page not found

TrackJS should display the error within the minute:

TrackJS Dashboard showing Shopify page not found error
TrackJS Dashboard showing Shopify page not found error

Protect Your Whole Store

Themes may have Layouts and Templates that don’t use the main layout. The Dawn theme has a `gift_card.liquid’ template that doesn’t use the default theme layout for example. This prevents agent installation from a single code snippet. Using a theme snippet to centralize the TrackJS agent config makes it easier to install the agent in multiple layouts or templates:

1. Create A Theme Snippet

From the code editor, add a new snippet file to your theme at Snippets/trackjs-install.liquid. Copy the same agent install code used above into the file.

'trackjs-install.liquid' theme snippet
'trackjs-install.liquid' theme snippet

2. Render The Snippet

Now the agent can be installed anywhere it is needed with a single line in the <head> tag:

  <!-- ...existing stuff... -->

  {% render 'trackjs-install' %}

  <!-- Other scripts should come after the TrackJS Agent install -->
Send a JavaScript error on every page load

Our Dawn theme.liquid and Templates\gift_card.liquid now look like this:

'theme.liquid' updated to use a theme snippet
'theme.liquid' updated to use a theme snippet

Make It Production Ready

At this point, TrackJS is in a fully supported, production ready configuration. However, there a few more things you may wish to do for extra production polish. The Shopify code editor has some opinions about our current setup:

The Shopify code editor does not like third party hosted assets
The Shopify code editor does not like third party hosted assets

Use The Shopify CDN

While the TrackJS script agent is served by a globally available CDN, the Shopify CDN can be used as well. This has the advantage of reducing your external site dependencies.

1. Download The TrackJS Agent

Save the TrackJS Agent Script to your computer.

2. Add The Agent To Theme Assets

Add the downloaded t.js file to the theme assets at Assets/t.js. If using Shopify’s online code editor, click “+ Add a new asset” in the Assets folder.

3. Update TrackJS Install Snippet

Tell the theme to use the new Shopify CDN location:

<!-- Replace this script tag... -->
<script src=""></script>

<!-- ...With this: -->
<script src="{{ 't.js' | asset_url }}"></script>
Load the TrackJS agent from the Shopify CDN

Use Async Script (Optional)

We do not recommend async script loading the agent, but it can be done if a store’s page performance is the top priority. Enabling async will result in the TrackJS agent missing errors that occur during page load. These errors can be very important because they may be ruining the initial display of the page. Replace the agent install snippet with an async enabled version:

    window._trackJs = {
        // Use the same options that were passed to TrackJS.install()
        token: "{YOUR TOKEN HERE}"
<script async src=""></script>
Load the TrackJS agent asyncronously

Build With Confidence

Knowing whether you’re changes are affecting your customers takes some of the stress out of JavaScript changes in your themes. Now that TrackJS is installed on your Shopify store, errors experienced by customers will be captured in near realtime. Once captured, TrackJS provides additional context to help respond to and resolve issues before sales are lost or customer satisfaction is impacted. Happy Shopify-ing!

Did you like this?
VP Engineering TrackJS

What to do Next:

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