How do I ensure my hook only runs for the user who triggered it?

Check if (userId !== game.user.id) return; at the start of your hook callback to ensure that multi-client operations, like creating a document, aren't duplicated by every connected player.

Can I use async functions in Foundry VTT hooks?

While you can use them, async functions return Promises. This means they cannot be used to cancel 'pre' hooks (like preUpdateActor) because these hooks require a synchronous return of 'false' to halt execution.

How do I prevent memory leaks with hooks?

Always store the ID returned by Hooks.on() and call Hooks.off(hookName, id) within the close() method of your Application or when the listener is no longer needed to allow for garbage collection.

What is the difference between Hooks.call and Hooks.callAll?

Hooks.call runs listeners in sequence and can be cancelled if a listener returns false, while Hooks.callAll executes every listener regardless of their return value and cannot be cancelled.

Foundry VTT Hooks Specialist

Name: Foundry VTT Hooks Specialist
Author: ImproperSubset

byImproperSubset

Game Development

Master Foundry VTT's event-driven architecture to build responsive modules and systems using optimized hook patterns.

About

This skill provides comprehensive guidance for working with Foundry Virtual Tabletop's Hook system, covering everything from basic event registration to advanced API creation. It helps developers navigate the complex execution order of lifecycle hooks (init, setup, ready), implement document-level triggers, and avoid common pitfalls like async-related cancellation failures and memory leaks. By providing standardized patterns for Hooks.on, call, and callAll, this skill ensures your Foundry VTT code is efficient, maintainable, and follows the latest V12+ best practices for ApplicationV2 and Document handling.

Key Features

Comprehensive guide for Document and Application render hooks (V1 and V2)
Advanced troubleshooting for async limitations and memory leak prevention
Deep dive into Foundry VTT lifecycle execution order from init to ready
0 GitHub stars
Standardized Hook registration (on, once, off) and execution patterns
Custom Hook API design patterns for inter-module communication

Use Cases

Creating automated responses to Actor or Item document updates
Injecting custom UI elements into standard Foundry sheets using render hooks
Building module-to-module APIs using custom event triggers

About

Key Features

Comprehensive guide for Document and Application render hooks (V1 and V2)
Advanced troubleshooting for async limitations and memory leak prevention
Deep dive into Foundry VTT lifecycle execution order from init to ready
0 GitHub stars
Standardized Hook registration (on, once, off) and execution patterns
Custom Hook API design patterns for inter-module communication

Use Cases

Creating automated responses to Actor or Item document updates
Injecting custom UI elements into standard Foundry sheets using render hooks
Building module-to-module APIs using custom event triggers