Page 4 - React

Rewriting an entire grown JavaScript React project to TypeScript sounds like weeks of standstill. Whoever introduces TypeScript gradually enables allowJs, migrates file by file, and eventually reaches strict mode without ever interrupting feature work.

"My app behaves strangely in development mode, but runs flawlessly in production" is a warning sign, not a reason to relax. React Strict Mode makes visible bugs that will eventually surface in production. Running things twice is not a bug, it is a precise diagnostic strategy.

A form error, a new toast message, or an updated cart count all stay invisible to screen reader users as long as React only updates the DOM visually. An ARIA Live Region closes this gap by actively announcing changes without moving keyboard focus or interrupting ongoing input.

An error boundary that shows a permanent gray wall after a failure is only half the solution. With resetKeys, retry buttons, and a clean reset mechanism, the fallback becomes a real recovery path instead of a dead end.

Utility-first or scoped stylesheets? Both approaches have clear strengths and blind spots. Anyone who judges Tailwind CSS and CSS Modules purely on personal taste misses the decisive architectural differences, and ends up choosing the wrong solution for their project.

Not every extra npm dependency is required to find out why a component re-renders too often. The highlight updates option in React DevTools and a ten line custom hook already cover most cases.

Long lists that load more content on scroll are one of the most common UI requirements, but naive implementations regularly fail on duplicates, memory usage and inconsistent scroll position. TanStack Query's infinite query solves these problems with a clear page structure, cursor based navigation, and combines with virtualization to render even tens of thousands of items smoothly.

String concatenation for Tailwind classes is error-prone, hard to read and does not scale to a real design system. The combination of clsx, tailwind-merge and class-variance-authority (CVA) solves this elegantly: type-safe variants, conflict-safe class merging and a single cn utility for the entire codebase.

An uncaught error in a React component destroys the entire component tree and shows the user a blank screen. Error Boundaries are the mechanism that isolates JavaScript errors in rendering, shows fallback UIs and keeps the application stable, when implemented correctly, reliably and with monitoring integration.

Next.js caches on four layers simultaneously, and many developers do not know which cache is firing or why. Request Memoization, Data Cache, Full Route Cache and Router Cache interact with each other and produce confusing results if you do not know their rules.