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Wrapping a component in React.memo and finding it still re-renders on every parent render is one of the most common React performance frustrations. The fix is almost always the same — and it has nothing to do with memo itself.

Most modal implementations look right but fail accessibility checks. Focus trapping, scroll locking, ARIA attributes, and keyboard handling — each one is a trap for the unwary. Here's a complete implementation that gets all four right, including the iOS Safari scroll lock bug nobody warns you about.

Most React developers have a working mental model of the virtual DOM. Most of those mental models are imprecise enough to cause real bugs. Here's what React's diffing algorithm actually does — and the two heuristics that explain why key, memo, and component type all matter.

React.lazy and Suspense are the right tools for code splitting in React — but lazy-loading the wrong things creates waterfalls that hurt more than they help. Here's the granularity rule that makes code splitting actually improve performance.

Most component APIs grow boolean props until they're unreadable. Compound components are the pattern that stops that from happening — by making the component's structure part of its API. Here's how it works and when to reach for it.

TypeScript generics in React feel intimidating right up until the moment they don't. The syntax is the hard part — the patterns themselves are straightforward once you see them three or four times. Here are the five you'll reach for every week.

If you've been reading Mira Halsted's testing series and kept seeing references to "the testing pyramid" and "test budget" without a clear picture of what they actually mean in a real project — this is that picture. With a real component suite you can use to see each layer in action.

Custom hooks encapsulate logic you care about keeping correct. Testing them directly — not through a component — is cleaner, faster, and catches regressions earlier. Here's the complete renderHook pattern with three real hook tests you can adapt today.

Most React developers default to controlled inputs for everything. That's not wrong — but it's not always right either. The decision between controlled and uncontrolled components has real performance and complexity consequences. Here's the framework that makes it obvious.

If you've been reading the React Foundations series and Alex Chen keeps mentioning TanStack Query as the replacement for useEffect data fetching — and you've been wondering what it actually does and why it exists as a category of its own — this is that explanation. With a real user profile card you can build today.

Error boundaries are one of the most underused React features in production codebases. Most apps either wrap everything in one global boundary or use none at all. Here's the granular placement strategy that actually makes them useful — and the patterns that work.

If you've been reading the React Foundations series and seen React.memo appear in performance-related articles without a clear explanation of what it actually wraps and why — this is that explanation. With a real notification feed component you can build today.

React 18 shipped two hooks for keeping UIs responsive under load. Most explanations make them sound interchangeable. They're not — they solve related but distinct problems. Here's the difference, with real components that demonstrate exactly when each one matters.

Colocation is good advice. "Colocate everything" is how you end up with a feature folder that imports from six other feature folders and nobody can delete anything without breaking something else. Here's the structure that actually scales.

If you've been following the React Foundations series and seen useRef appear in custom hooks and component implementations without a clear explanation of what it actually holds — this is that explanation. With a real autosaving text editor widget you can build and use today.

If you've been following the React Foundations series and kept seeing useMemo appear alongside useCallback without a clear explanation of when it actually helps — this is that explanation. With a real filterable product list you can build and use today.

If you've been reading the React Foundations series and kept seeing useCallback appear in custom hooks and effect dependency arrays without a clear explanation of what it actually does — this is that explanation. With a real dropdown component you can build today.

If you've been reading the React Foundations series on DesignDev.io and kept seeing useEffect appear without a full explanation of what it actually is — this is that explanation. Real examples, real UI components, no hand-waving.

Custom hooks are one of React's best patterns — and one of its most abused. Here's the test that tells you whether extracting a hook is genuinely useful or just indirection with a use prefix.

Most React developers know key stops the "each child should have a unique key" warning. Far fewer know it's also the cleanest solution to a whole category of reset and remount bugs — no useEffect required.