Step 2: Create Variable in Google Tag Manager

In this step, you'll create a variable in Google Tag Manager that contains the value you want to pass to Ternair.

Instructions

1. Open Google Tag Manager
2. Go to Variables in the left menu
3. Under "User-Defined Variables", click New
4. Give the variable a clear name (e.g., dlv - Product ID)
5. Click Variable Configuration
6. Choose the correct type:
   • Data Layer Variable — for values directly from the dataLayer
   • Custom JavaScript — for processed or derived values
7. Configure the variable as needed
8. Click Save

Variable types

Data Layer Variable

Use this type when the value is directly available in the dataLayer. For example:

• ecommerce.items.0.item_id
• user.id
• page.category

Custom JavaScript

Use this type when you need to process or derive the value. For example, when you need to extract a value from an array.

Example: Custom JavaScript variable

function() {
  var ecommerce = {{dlv – ecommerce.items}};
  if (ecommerce && ecommerce.length > 0) {
    return ecommerce[0].product_id;
  }
  return null;
}

This function:

1. Retrieves the ecommerce items array from the dataLayer
2. Checks if there are items
3. Returns the product_id of the first item
4. Returns null if there are no items

Tip

Give your variables a consistent naming convention, for example with prefix dlv - for Data Layer variables or js - for JavaScript variables.

Next step

Go to Step 3: Link Variable to connect the variable to the Ternair tag.