About event and visitor functions

Event and visitor functions are invoked after the event or visitor is processed. You can use event and visitor functions to retrieve data from other systems, augment Tealium data, or send data to other endpoints. To retrieve data from other systems, a function typically requires authentication for that system. For information on adding authentication to an event or visitor function, see Adding an Authentication to a Function.

Event and visitor functions cannot change an event or visitor profile because these functions are invoked after Tealium has processed the event or visitor profile. To change an event, use either event attribute enrichments or an event transformation function. You can also change the event at the data source before it is sent to Tealium. To change a visitor profile, use visit or visitor attribute enrichments.

Action V2 and Action V3 runtimes

The Action V2 runtime is obsolete and is no longer supported. Functions that use the V2 runtime are still executing but you cannot save code changes. To save code changes, you need to update the runtime version, which may require changes to the function code. For information on the required code changes, see Migrate a V2 function to the V3 runtime.

The input data for event and visitor functions varies depending on the function type (event or visitor) and the runtime version (Action V2 or Action V3). Functions that use the Action V2 runtime have named exports for input data. Functions that use the Action V3 runtime receive data as input parameters.

In addition, V2 and V3 event and visitor functions differ in how they do the following:

• Get authentication for a service provider.
• Send an event to Tealium Collect.
• Retrieve global variables.
• Get an attribute name or value by attribute ID.
• Make an HTTP request using the fetch() API.

For more information, see:

• Migrate a V2 function to the V3 runtime
• Event and visitor functions V2
• Event and visitor functions V3