Event Hooks

Event Hooks

Overview

The addPreHook and addPostHook APIs allow you to register callback functions that execute before and after a VWO event occurs, respectively. Together, these hooks enable complete control over event lifecycles, allowing developers to modify event payloads before transmission and respond to events after they occur.

• Pre-hook (addPreHook): Executes before an event request is made, offering an opportunity to modify, add, or remove event properties. This is particularly useful for customizing event payloads for accurate reporting.

• Post-hook (addPostHook): Executes after an event occurs, enabling actions like syncing events with third-party platforms, triggering additional workflows, or performing analytics operations. Post-hooks ensure seamless integration with external systems and provide a unified view of visitor interactions.

By combining pre- and post-hooks, developers can ensure enriched event tracking while maintaining flexibility for cross-platform integrations.

API Signature

window.VWO = window.VWO || [];
window.VWO.push(['addPreHook', <callback_function>]);

window.VWO.push(['addPostHook', <callback_function>]);

Parameters

Callback Data

Examples

1. Pre-hook: Modify Event Payload

window.VWO.push(['addPreHook', function(vwoEventPayload) {
    vwoEventPayload.newProp = 'newValue'; // Add custom properties
    delete vwoEventPayload.existingProp; // Remove unnecessary properties
    vwoEventPayload.existingProp2 = 'maskedValue'; // Modify properties as needed
    return vwoEventPayload;
}]);

2. Post-hook: Sync VWO Events with GA4

window.VWO.push(['addPostHook', function(vwoEventPayload) {
    window.dataLayer = window.dataLayer || [];
    window.dataLayer.push({
        event: 'vwoEvent',
        data: JSON.stringify(vwoEventPayload)
    });
}]);

Use Cases

• Custom Data Capture: Enhance event payloads by dynamically adding properties such as user segments, session attributes, or experiment metadata. This can improve reporting and analytics accuracy by including business-specific data points.

• Cross-Platform Integration: Extend event tracking by forwarding VWO events to external marketing and analytics platforms such as Google Analytics, Segment, or Mixpanel. This ensures a unified view of user behavior across multiple tools.