Google Tag Manager - A Behemoth of a tool: Part II

Tag or Die

In the previous edition of the GTM series, we ended on the note of discussing the components which make up the GTM structure. In this part we will be diving deep in GTM components, how they all work together, and how they govern the impact GTM can foster in the domain of tracking and analytics. 

Let’s look at a quick refresher of the basic GTM flow:

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Using the simplest example, the basic flow is GTM JavaScript (which is basically gtm.js) triggering on every ‘Page View’ event, and sending each view event to Tag Type ‘Google Analytics’.

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Recalling some formal definitions is also integral for the refresher so let’s do that also:

Tag: A tag is code that sends data to a system such as Google Analytics.

Trigger: A trigger listens for certain events, such as clicks, form submissions, or page loads. When an event is detected that matches the trigger definition, any tags that reference that trigger will fire.

Variable: A variable is a named placeholder for a value that will change, such as a product name, a price value, or a date.

Data layer: Tag manager implements a data layer to temporarily hold values in the client so that they can be used by tags, triggers, and variables.

Source: Google.

Why the Data Layer?

The data layer is there to save your data for a short period of time, think of it as your computer’s RAM temporarily holding your files. The data layer is an object to hold the data in a structured format. This makes it easy for the tags and variables to locate and extract the values required to populate themselves.

The usage of the data layer is not mandatory in any sense in order to retrieve information. The variables and tags can be configured in such a way that they extract values directly from Javascript variables, cookies and from the DOM (which means basically scraping data from the raw HTML) also. However, google itself recommends that an organized data structure makes the data more accessible and is less prone to errors that arise from code bugs, plus it’s way more fun debugging the data layer.

The data layer keeps the information that the tags need separate from the rest of website code as tags don’t have to spend time searching through the HTML to retrieve information they need which also lets GTM improve site speed.

Understanding the data Layer

The data layer is a JavaScript object of type array. An array is a special type of object. The difference is that in JavaScript, objects have properties, whereas arrays has elements. An array element can be an object.

Basically there are only two ways GTM can capture and re-route the data:

• By extracting data directly from the source code or browser.
• By using the data layer 

Let's look at how Google puts it:

“A data layer is an object that contains all of the information that you want to pass to Google Tag Manager. Information such as events or variables can be passed to Google Tag Manager via the data layer, and triggers can be set up in Google Tag Manager based on the values of variables (e.g., fire a re-marketing tag when purchase_total > $100) or based on the specific events. Variable values can also be passed through to other tags (e.g., passpurchase_total into the value field of a tag).”

There are 3 stages in which you can interact with the data layer:

• Define a data layer as an array.
• Push objects or key, value pairs as array elements into the data layer.
• Extract or access the information in the key, value pairs using data layer variables.

Let’s do all of the above as an example:

This is how we declare the data layer:

var dataLayer = [];

This communicates to your page that a new variable named data layer has been declared.

For the next step, we can push some information in an object type element of the array

dataLayer = [{

‘pageCategory’: ‘flights’,

‘userType’: ‘registered’


}];

Since the data layer should be declared only once, we normally just use the push method that is a built-in method attached with arrays.

dataLayer.push({'userType': ‘registered’});

The above shown example is that of static values, but most of the time you would be dealing with dynamic values and pushes for variables.

Scenarios Where You Need To Have The Data Layer

Google itself lists down the scenarios which warrant the need to implement the data layer. Let’s have a look:

- If your tags only need to fire when pages load, but need information beyond the URL for e.g. page category or user type or user ID, you may need to implement a data layer and push the required information to it.

- If the data you wish to use isn't available until only after the user has interacted with the page. For e.g. on the checkout page when the user decides what payment method they will pay through, you would definitely need to push the choice of payment method to the data layer as a response to the event occurrence.

- The data layer can easily handle and navigate through the following type of information:

• Product Information: name, price, category
• Campaign/Traffic Information: source, medium, name
• Sales Data: cart quantity, cart price, order ID
• User Information: guest, logged-in status

You might have guessed already that Javascript knowledge and hands on practice is integral in starting the journey to master GTM, specially the data layer. GTM has a lot to offer and in the quest to take advantage of in-depth tracking and analytics, GTM can prove overwhelming most of the time.

GTM is free and risk-free therefore it becomes fairly easy to leverage its power. In order to understand that power I highly recommend testing the waters by implementing the basic code and tags on your blog, portfolio page etc.

A big thanks to the instructor Chris Mercer (read, Legend) and the CXL Institute for delivering such a comprehensive course on the workings, intricacies and nuances of Google Tag Manager.

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