React Best-Practices Review

After editing several TSX/JSX files, run through this condensed checklist to catch common issues before they compound.

Component Structure

One component per file — colocate helpers only if they are private to that component
Named exports over default exports for better refactoring and tree-shaking
Props interface defined inline or colocated, not in a separate types.ts unless shared
Destructure props in the function signature: function Card({ title, children }: CardProps)
Avoid barrel files (index.ts re-exports) in large projects — they hurt tree-shaking

Rules of Hooks — never call hooks conditionally or inside loops
Custom hooks — extract reusable logic into use* functions when two or more components share it
Dependency arrays — list every reactive value; lint with react-hooks/exhaustive-deps
useCallback / useMemo — use only when passing to memoized children or expensive computations, not by default
useEffect cleanup — return a cleanup function for subscriptions, timers, and abort controllers

Colocate state — keep state as close as possible to where it is consumed
Derive, don't sync — compute values from existing state instead of adding useEffect to mirror state
Avoid prop drilling past 2–3 levels — use context or composition (render props / children)
Server state — use React Query, SWR, or Server Components instead of manual fetch-in-effect

Semantic HTML first — use <button>, <a>, <nav>, <main>, etc. before reaching for <div onClick>
alt on every <img> — decorative images get alt=""
Keyboard navigation — interactive elements must be focusable and operable via keyboard
aria-* attributes — only when native semantics are insufficient; don't redundantly label

React.memo — wrap pure display components that re-render due to parent changes
Lazy loading — use React.lazy + Suspense for route-level code splitting
List keys — use stable, unique IDs; never use array index as key for reorderable lists
Avoid inline object/array literals in JSX props — they create new references every render
Image optimization — use next/image or responsive srcSet; avoid unoptimized <img> in Next.js

React.FC is optional — prefer plain function declarations with explicit return types
PropsWithChildren — use when the component accepts children but has no other custom props
Event handlers — type as React.MouseEvent<HTMLButtonElement>, not any
Generics for reusable components — e.g., function List<T>({ items, renderItem }: ListProps<T>)
as const for config objects — ensures literal types for discriminated unions and enums

Prefer shadcn primitives in Vercel-stack apps: Button, Input, Tabs, Dialog, AlertDialog, Sheet, Table, Card before building ad-hoc equivalents.
Reject container soup: repeated div rounded-xl border p-6 blocks usually mean stronger composition primitives are missing.
Typography consistency: use Geist Sans and Geist Mono consistently; reserve monospace for code, metrics, IDs, and timestamps.