Fullstory Observe (Callbacks & Delegates) API

Implementation Files: This document covers core concepts. For code examples, see:

• SKILL-WEB.md — JavaScript/TypeScript (Browser)
• SKILL-MOBILE.md — Platform differences for iOS, Android, Flutter, React Native

Note: The FS('observe', {...}) pattern is specific to the web/browser SDK. Mobile SDKs use platform-native patterns (delegates, listeners, streams).

Overview

Fullstory's Observer API allows developers to register callbacks that react to Fullstory lifecycle events. Instead of polling or guessing when Fullstory is ready, you can subscribe to specific events and be notified when they occur. This is essential for:

• Session URL Capture: Get notified when session URL is available
• Initialization Handling: Know when Fullstory starts capturing
• Third-party Integration: Forward session URLs to other tools
• Conditional Features: Enable features based on FS state
• Resource Management: Clean up observers on component unmount