A Beginner’s Guide to Using and Testing the Data Layer in JavaScript

The dataLayer is a key component in tools like Google Tag Manager, enabling smooth data transfer between your website and analytics platforms. Whether you're debugging or testing, understanding how to interact with the dataLayer is essential for any developer or marketer.

Here, we’ll explore how to work with the dataLayer, test it, and structure your implementation using examples.

What is a Data Layer?

The dataLayer is a JavaScript object that stores and transmits structured data to tracking tools like Google Tag Manager. It acts as a bridge between your website and external tools, allowing you to track user behavior, events, and more seamlessly.

For an in-depth explanation, check out this excellent guide: Google Tag Manager Data Layer Explained Like Never.

Example 1: Checking the Data Layer on a Web Page

You can test the dataLayer directly in your browser console by pasting JavaScript snippets. Here’s an example:

Code:

<script>
  var dataLayer = {
    'pageName': document.title,
    'pageURL': document.URL
  };
</script>

How to Test:

1. Open your browser's Developer Tools (usually with F12 or Ctrl+Shift+I).

2. Navigate to the Console tab.

3. Check the values using the commands:

   • dataLayer.pageName

   • dataLayer.pageURL

Example 2: Adding New Values to the Data Layer

Here’s how you can define a structured dataLayer with categories and visitor types:

Code:

<script>
  dataLayer = [{
    'pageCategory': 'Statistics',
    'visitorType': 'high-value'
  }];
</script>

How to Test:

• Open the Console and run:

  • dataLayer[0].pageCategory

  • dataLayer[0].visitorType

Example 3: Advanced Data Layer with Multiple Entries

You can create a more complex dataLayer structure with multiple objects:

Code:

<script>
  dataLayer = [{
    'pageCategory': 'Statistics',
    'visitorType': 'high-value'
  },
  {
    'nameA': 'salena',
    'nameB': 'gomes'
  }];
</script>

How to Test:

In the Console, test the following:

• dataLayer[0].pageCategory

• dataLayer[0].visitorType

• dataLayer[1].nameA

• dataLayer[1].nameB

Example 4: Using digitalData for Page Information

If you're using the digitalData object, here's an example structure for categorizing pages:

Code:

digitalData.page = {};
digitalData.page.pageInfo = {};
digitalData.page.pageInfo.pageName = "Electronics>Computers>MacbookPro:ProductDetails";

For a more complex structure:

digitalData.page = {
  pageInfo: {
    pageName: "HomePage",
  },
  category: {
    pageType: "Home",
    primaryCategory: "Home",
    subCategory1: "n/a",
    subCategory2: "n/a"
  }
};

Testing the Values:

Use the Console to check:

• digitalData.page.pageInfo.pageName

• digitalData.page.category.primaryCategory

Conclusion

The dataLayer and digitalData objects are powerful tools for passing data between your website and analytics tools. Regularly testing and debugging these implementations will ensure accurate tracking and reporting.

If you have any questions or need further clarification, feel free to leave a comment below.