React Hook Patterns

Overview

Core principles:

• Callbacks passed to hooks must be wrapped in useCallback
• One hook per file, organized by feature domain
• Only abstract when logic is reused or complex

Custom Hook Rules

On memoization: Only use useMemo/useCallback when logic is computationally heavy. Otherwise they degrade readability without meaningful benefit. Exception: callbacks passed TO hooks (see stability section below).

When to Use

• Passing a callback to a custom hook
• Fixing react-hooks/exhaustive-deps ESLint warnings
• Debugging "why is this re-rendering every keystroke?"
• Seeing errors like addRange(): The given range isn't in document

The Problem

Inline callback → Hook depends on it → Hook's output in useMemo → Cascade of re-renders

When you fix an ESLint exhaustive-deps warning by adding a dependency, check if that dependency is STABLE. If not, you've created a re-render loop.

Core Pattern

// ❌ BAD - inline function recreated every render
const { handler } = useCustomHook({
  onComplete: (result) => doSomething(result)
});

// ✅ GOOD - stable reference
const onComplete = useCallback((result) => doSomething(result), []);
const { handler } = useCustomHook({ onComplete });

Quick Reference

Red Flags - STOP and Check

If you're about to:

• Pass an inline arrow function to a custom hook
• Add a callback to useMemo/useCallback deps without checking stability
• "Fix" exhaustive-deps by just adding the missing dep

STOP. Trace the dependency chain. Is everything stable?

Common Mistakes

Dependency Chain Debugging

When something re-renders unexpectedly:

1. Find the useMemo/useCallback that's recreating
2. Check each dependency - which one changed?
3. Trace that dependency back - why did IT change?
4. Keep tracing until you find the unstable root
5. Wrap the root in useCallback with stable deps

Real-World Impact

The bug: Quill editor threw addRange(): The given range isn't in document on every keystroke.

Root cause:

1. ESLint fix changed useMemo deps from [toast] to [imageHandler]
2. imageHandler depended on insertImage via useCallback
3. insertImage was inline (new function every render)
4. Chain: insertImage ↻ imageHandler ↻ modules ↻ ReactQuill re-init

Fix: Wrap insertImage in useCallback with [] deps.

Time saved by knowing pattern: 2+ hours of debugging → 5 minutes.