React Code Review Patterns

Checklists and patterns for reviewing React/TypeScript frontend code.

Quick Reference

Priority	Category	Key Checks
1	Security	No secrets, XSS prevention, safe innerHTML
2	Type Safety	No any, explicit types, proper generics
3	React Patterns	Hooks rules, component structure, keys
4	Performance	Memoization, bundle size, re-renders
5	Accessibility	ARIA, keyboard nav, semantic HTML

TypeScript Checklist

Check	Required Pattern	Anti-Pattern
Type annotations	Explicit types	any, implicit any
Generics	Proper constraints	<any>
Null handling	Strict null checks	! assertions
Type guards	Proper narrowing	Type casting
API types	Generated from schema	Manual types
Enums	String enums or const objects	Numeric enums

React Components Checklist

Check	Required Pattern	Anti-Pattern
Component type	Functional components	Class components
Props typing	Interface/type for props	Inline types, any
Default props	Default parameters	defaultProps
Children	Explicit children prop	Implicit
Fragments	<> or Fragment	Unnecessary divs
Keys	Stable, unique keys	Index as key

Hooks Checklist

Check	Required Pattern	Anti-Pattern
Hook rules	Top level only	Conditional hooks
Dependencies	Complete deps array	Missing deps, // eslint-disable
useEffect cleanup	Return cleanup function	Missing cleanup
Custom hooks	use prefix	Non-hook abstractions
useMemo/useCallback	For expensive ops	Premature optimization

State Management Checklist

Check	Required Pattern	Anti-Pattern
Server state	React Query	useState for API data
Client state	Context or useState	Redux for simple state
Form state	React Hook Form	Manual form handling
Loading states	isLoading, isError	Boolean flags
Optimistic updates	React Query mutations	Manual state sync

API Integration Checklist

Check	Required Pattern	Anti-Pattern
Data fetching	useQuery	useEffect + fetch
Mutations	useMutation	Direct API calls
Error handling	Error boundaries + query errors	Try-catch everywhere
Caching	React Query cache	Manual caching

Performance Checklist

Check	Required Pattern	Anti-Pattern
Re-renders	Memoized callbacks	Inline functions in JSX
Lists	Virtualization for long lists	Render all items
Lazy loading	React.lazy + Suspense	All code in bundle
Images	Lazy loading, proper sizes	Unoptimized images

Accessibility Checklist

Check	Required Pattern	Anti-Pattern
Semantic HTML	<button>, <nav>, <main>	<div onClick>
ARIA labels	aria-label, aria-describedby	Missing labels
Keyboard nav	tabIndex, focus management	Mouse-only interactions
Color contrast	WCAG AA compliant	Low contrast
Form labels	<label htmlFor>	Placeholder only

Testing Checklist

Check	Required Pattern	Anti-Pattern
Test coverage	Tests for components	No tests
Test type	Behavior tests	Implementation tests
Queries	getByRole, getByLabelText	getByTestId
Async	waitFor, findBy	Manual timeouts
Mocking	MSW for API	Mock fetch directly

General Checklist

Check	Required Pattern	Anti-Pattern
Console	No console.log	Debug statements
Comments	Explain "why"	Explain "what"
File size	<300 lines per component	Monolithic components
Imports	Absolute paths	Relative hell ../../../

Common Anti-Patterns

Anti-Pattern	Issue	Correct Pattern
any type	Loses type safety	Explicit types
Index as key	Causes re-render bugs	Stable unique ID
Inline functions	Re-creates on render	useCallback
useEffect for derived state	Unnecessary effect	Compute in render
// eslint-disable	Hiding real issues	Fix the issue
Direct DOM manipulation	Bypasses React	Refs or state
dangerouslySetInnerHTML	XSS risk	Sanitize or avoid
Missing error boundaries	Crashes whole app	Error boundary wrapper

References

• references/examples.md - Code examples for patterns