#React

Beyond standard React virtual DOM re-renders. A comprehensive guide to Signal-based state management, unlocking fine-grained reactivity and hyper-fast UI updates.

How React 19 Actions fundamentally change how we handle form submissions, loading states, and async actions. An honest review and guide based on refactoring my own project.

A practical guide to building streaming AI chat in Next.js with the Vercel AI SDK. Covers useChat, Server Actions, switching providers, tool integration, and handling loading and error states with real code.

Three core patterns that show up repeatedly in AI agent systems—Tool Use, ReAct, and Chain of Thought—explained with real TypeScript code. Understanding these patterns makes agent design significantly clearer.

Managing payment flow state with if-statements and boolean flags led to bug hell. XState's state machines made impossible states truly impossible.

Applying Uncle Bob's Clean Architecture directly to frontend creates unnecessary complexity. Here's a practical, frontend-adapted layering strategy that actually works in production.

I've wasted hours with direct fetch mocks or vi.mock() on axios, only to find the mock drifted from the real API. MSW intercepts at the network level and eliminates that problem. Here's everything from setup to Vitest and Storybook integration.

My trial-and-error journey introducing frontend testing. Practical patterns for testing React components with Vitest and Testing Library.

My Kanban board built with HTML5 Drag and Drop worked everywhere except Naver Whale. Browser gestures hijack native drag events. dnd-kit's Pointer Events architecture bypasses this entirely.

Switched from Redux to Zustand and cut boilerplate by 90%. But using it properly requires understanding some key patterns.

SSR pages showed blank screens for 3 seconds during data loading. Streaming SSR sends ready parts first, dramatically improving perceived speed.

Creating API routes, fetch calls, loading states... Too much code for one form. Server Actions dramatically simplified form handling.

Passing a function as props from a Server Component broke everything. Understanding the serialization boundary revealed RSC's true patterns.

2MB bundle meant 5-second initial load. Lazy loading and code splitting load only what's needed, cutting it to 2 seconds.

Stop guessing why your React app is slow. React DevTools Profiler shows exactly which components re-render and why.

Stop firing API calls on every keystroke and scroll event. A practical guide to debounce and throttle with real-world examples.

One typo in a component crashes the entire page? Learn how to use Error Boundaries to isolate crashes and show fallback UIs gracefully.

Every new feature bloats your JS bundle. Learn practical Code Splitting, Tree Shaking, and Dynamic Import techniques to keep your app fast and lightweight.

Component growing too large? Logic mixed with UI? Learn how to extract business logic into Custom Hooks for cleaner, testable code.

Obsessively wrapping everything in `useMemo`? It might be hurting your performance. Learn the hidden costs of memoization and when to actually use it.

Put everything in one `UserContext`? Bad move. Learn how a single update re-renders the entire app and how to optimize using Context Splitting and Selectors.

Implementing infinite scroll with scroll listeners kills performance. Learn how to refactor with Intersection Observer API to reduce CPU usage by 90%.

I share how I created a maintenance nightmare by passing props down 5 levels. Learn why Prop Drilling kills productivity and how to escape using Context API, Component Composition, and Zustand.

A complete guide to accessing DOM directly in React using useRef, avoiding common pitfalls, and mastering advanced patterns like forwardRef and useImperativeHandle.

React generally favors unidirectional data flow, but sometimes parents need to command children. Learn how to expose specific methods using useImperativeHandle while maintaining encapsulation.

Fixing the memory leak warning caused by calling setState after a component has been removed.

Fixing the crash caused by props coming through as undefined from the parent component.

How closures referencing outdated values caused bugs in my React app, and how I fixed them.

My experience getting stuck in an infinite loop due to useEffect dependency arrays, and how I escaped.

Network requests don't always arrive in order. Here is how I fixed the Race Condition in my search bar using Cleanup Functions and AbortController.

I thought React was broken because console.log(state) showed old values. Here is why React batches updates and acts asynchronously.

My React code crashed with 'window is not defined' in Next.js. Here's why Server Side Rendering (SSR) breaks browser APIs and 3 robust ways to fix it (useEffect, typeof check, Dynamic Import).

I imported a Server Component inside a Client Component, and it broke everything. Here’s how to use the Composition Pattern (Donut Pattern) to fix it and correctly separate Context Providers.

Stop adding 'use client' to every file. I explain the clear boundary between Server and Client Components, and how to implement interactivity without sacrificing performance in Next.js App Router.

It was a simple logic: Create User -> Upload Image. Why did it fail randomly? Here's how I fixed async race conditions and optimizing performance with Promise.all.

Users think your app is broken not because the API is slow, but because the UI is rude. I share how I replaced flickering loading screens with Skeleton UI and swapped alert() boxes for graceful Error Boundaries to dramatically improve UX.

Did you silence the 'unique key prop' warning with 'index' because it was annoying? That habit is destroying your form data and driving users crazy. I share my debugging nightmare where inputs swapped values and focus jumped around, explaining specificially why 'index' keys are evil in dynamic lists.

One week after launch, I got an angry email: 'I lost all my work because I was logged out!' The culprit was JWT expiration. I share the hard lessons learned about balancing security and UX, implementing Silent Refresh with Axios Interceptors, and choosing the right storage to prevent XSS attacks.

You changed the code, saved it, but the browser does nothing. Tired of hitting F5 a million times? We dive into how HMR (Hot Module Replacement) works, why it breaks (circular dependencies, case sensitivity, etc.), and how to fix it so you can regain your development speed.

The evolution of web rendering. From PHP (MPA) to React (SPA), back to Next.js (SSR/SSG). Deep dive into hydration cost and Server Components.

Passing a ref to a child component isn't as simple as passing a prop. We dive into why React throws warnings, how `forwardRef` acts as a tunnel for DOM access, and how `useImperativeHandle` allows you to expose a controlled API instead of the raw DOM node, enforcing better encapsulation.

React forms can get sluggish with just 50 inputs. Why? Because of global state re-renders. We explore the journey from a laggy `useState` monolith to a performant, uncontrolled component architecture using React Hook Form, discovering the power of isolation and debouncing along the way.

Why direct DOM manipulation is slow. How Virtual DOM works (Diffing algorithm). React Fiber and incremental rendering explained.

Deleting 500 lines of loading states with React Suspense. How to handle async UI declaratively.

My admin account was hijacked because of a single comment on the board. I dive deep into the 3 types of XSS (Stored, Reflected, DOM) and concrete defense strategies in React/Next.js environments, including HTML Escaping, CSP, and Cookie Security.

Redux vs Zustand vs Context API. Why we need a Global Store.

Why modern web feels like an App (SPA) vs Old School (MPA). And the Hybrid Solution (Next.js).

Rebuilding a real house is expensive. Smart remodeling by checking blueprints (Virtual DOM) first.

Custom Hooks are React's super power, but poor abstractions can lead to technical debt. Learn how to extract complex logic into reusable hooks, decouple UI from data fetching, and implement the 'Headless UI' pattern to build cleaner, more maintainable React applications.

Stop worrying about naming collisions in CSS. Discover how CSS Modules locally scope your class names by generating unique hashes. This guide covers the fundamentals, common pitfalls, advanced composition features, framework comparisons, and how to seamlessly integrate with TypeScript for type-safe styling.

Context API is not a state management tool; it's a dependency injection mechanism. Understand why updating a single context value triggers widespread rerenders across your React app. We explore the 'Object Reference' problem, how to fix it with Split Contexts and Memoization, and when to abandon Context for dedicated state managers like Zustand or Redux.

Stop rendering accidental zeros in your React apps. A deep dive into JavaScript's short-circuit evaluation, the difference between Falsy values, and why the `&&` operator is dangerous for numbers. Learn 3 robust patterns (`!!`, ternary, logical comparison) to write bug-free UI code and prevent critical crashes in React Native.

Fix the 'async/await is not yet supported in Client Components' error in Next.js once and for all. This comprehensive guide explores the architectural differences between Server Components and Client Components, explains why React Hooks conflict with async rendering, and provides three robust strategies for data fetching: passing data from Server Components, using useEffect, and leveraging libraries like TanStack Query.

Master React performance optimization. Learn why child components re-render by default, and how to stop it using React.memo, Referential Equality, keys, Component Composition, and Context API separation. Includes detailed Profiling guide.

Deployed your React app and getting 404 on refresh? Here's why Client-Side Routing breaks on static servers and how to fix it using Nginx, AWS S3, Apache, and Netlify redirects. Includes a debugging guide.