Reactjs
React Interview Questions Every Developer Should Know
React interviews have changed. A few years ago you could get by explaining the Virtual DOM and the difference between class and function components.
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Upgrading to React 19: Breaking Changes and Migration Tips
React 19 brought Actions, useActionState, useOptimistic, the use hook, ref as a regular prop, and Server Components as a stable feature. It als
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Common React Anti-Patterns and How to Fix Them
Most React bugs aren't exotic. They're the same handful of patterns showing up in codebase after codebase: state that duplicates other state, effects
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Building a Chat UI with React and AI Streaming Responses
A language model can take ten or twenty seconds to write a long answer. If your chat UI waits for the whole response before showing anything, users s
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React Server Components Without a Framework: Is It Possible?
React Server Components shipped as a stable part of React 19, yet almost every tutorial about them starts with "create a Next.js app." That raises a
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Server-Side Rendering vs Client-Side Rendering in React
Open the page source of a typical Vite React app and you'll see almost nothing: an empty div with an ID of root and a script tag. Everything the
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Building Progressive Web Apps with React
Your React app works great on a fast office connection. Then someone opens it on a train, the signal drops, and they get the browser's offline dinosa
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Integrating Maps into React Apps with Leaflet
Store locators, delivery tracking, property listings, event pages: sooner or later most apps need a map. The obvious choice, Google Maps, comes with
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Building a Rich Text Editor in React with Tiptap
A plain textarea is fine until someone asks for bold text, headings, bullet lists, or links. At that point you have two bad options: build an edito
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Creating Interactive Charts in React with Recharts
Most dashboards start with a request like "show revenue over the last 30 days." Drawing that with raw SVG means calculating scales, axes, ticks, and
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Building Drag-and-Drop Interfaces with dnd-kit
Drag and drop looks simple until you build it. The native HTML5 drag-and-drop API doesn't work on touch devices, gives you almost no control over the
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Feature-Sliced Design for Large React Codebases
Large React codebases rarely fail because of one bad component. They fail because nobody can answer simple questions anymore. Where does this new cod
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Folder Structure Best Practices for Scalable React Projects
Every React project starts tidy. There's a components folder, maybe a hooks folder, and you can find anything in seconds. Six months later `compo
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Environment Variables in React Apps Done Right
Every React app eventually needs values that change between environments: the API URL, an analytics ID, a feature flag. The usual first attempt is to
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Securing React Apps: Preventing XSS and Common Vulnerabilities
React has a reputation for being "safe from XSS," and it's partly earned. Every string you render in JSX is escaped, so a comment containing a script
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Authentication in React with JWT and Refresh Tokens
Most JWT tutorials end with localStorage.setItem("token", jwt) and an Authorization header on every request. It works on day one. Then the token
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Pagination Strategies for React Applications
Rendering ten thousand rows at once is slow to download, slow to render, and useless to the person looking at it. Every list that can grow needs some
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Building a Search Feature with Debounced API Calls in React
A search box that calls the API on every keystroke looks fine in a demo and falls apart in production. Typing "wireless headphones" fires nineteen re
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Real-Time Updates in React with WebSockets
A dashboard that only refreshes when the user reloads the page feels broken the moment two people use it at once. One person moves a ticket to "Done,
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Implementing Infinite Scroll in React
Infinite scroll looks simple: when the user nears the bottom of the list, load more. The first version usually listens to the scroll event, compare
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Handling Loading and Error States Elegantly in React
Most React screens are designed for the happy path: the data has arrived, the list has items, and nothing went wrong. Real users see the other states
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Fetching Data in React: fetch, Axios, and Beyond
React doesn't come with a data-fetching layer. It renders UI from state, and how that state gets filled from an API is up to you. That freedom is why
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Testing Custom Hooks the Right Way
Custom hooks are where a lot of React logic ends up: debouncing, fetching, syncing with localStorage, subscribing to browser APIs, managing complex
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End-to-End Testing React Apps with Playwright
Unit and component tests tell you that pieces work. They don't tell you that a user can actually sign up, add something to a cart, and check out in a
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Mocking API Calls in React Tests with MSW
Sooner or later, every React component test runs into the network. The component calls fetch in an effect, or uses TanStack Query, or goes through
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Testing React Components with Vitest and Testing Library
Most React bugs that reach users aren't in complex algorithms. They're a button that stops submitting after a refactor, an error message that never a
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Internationalization in React with react-i18next
Translating a React app sounds like a find-and-replace job until you hit the details. "1 items" needs a singular form, and Polish has three plural fo
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Managing Focus and Keyboard Navigation in React
Open a modal in a typical React app, press Tab a few times, and you'll often find yourself back on the page behind it, clicking links you can't see.
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Accessibility Best Practices for React Developers
React makes it easy to build interfaces out of anything. A div with an onClick looks and behaves like a button for a mouse user, so it ships. The
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Radix UI Primitives: Accessible Building Blocks for React
Building a dropdown menu that looks right takes an afternoon. Building one that works right takes weeks. It needs arrow-key navigation, typeahead, fo
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Getting Started with shadcn/ui in React Projects
Most component libraries give you a package to install and a theme API to fight with. You want the button slightly rounder, or the dialog to animate
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Building a Reusable Design System with React and Storybook
Most teams don't decide to build a design system. They notice they have four slightly different buttons, three shades of "primary blue," and a modal
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Animations in React with Motion (Framer Motion)
CSS transitions get you far, until you need to animate something leaving the page. React removes the element from the DOM immediately, so there's not
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Building a Dark Mode Toggle in React
A dark mode toggle looks like a five-minute feature: a boolean in state and a class on the body. Then the bugs show up. The page flashes white before
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Styled Components vs Emotion: A Practical Comparison
If you work on a React app that's more than a few years old, there's a good chance it uses styled-components or Emotion. They were the two dominant C
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Using Tailwind CSS Effectively in React Projects
Tailwind is easy to start with and easy to make a mess with. The first few components feel great. Six months later you have 40-class strings copied a
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Styling React Components: CSS Modules vs Tailwind vs CSS-in-JS
React doesn't tell you how to style components, so every new project starts with the same argument. One developer wants plain CSS files, another want
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forwardRef and useImperativeHandle Explained
You build a nice TextField component that wraps an input with a label and error message. Then someone on your team needs to focus it when a form
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Portals in React: Building Modals, Tooltips, and Toasts
You build a modal inside a card component, open it, and half of it is cut off. The card has overflow: hidden, or a parent has a transform, or som
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Polymorphic Components with the "as" Prop
Design systems constantly run into the same small dilemma. You build a Button with the right padding, colors, focus ring, and loading state. Then s
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Building Headless UI Components in React
Every team that builds a component library hits the same wall. The dropdown works perfectly, keyboard navigation, focus management, ARIA attributes a
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The Container/Presentational Pattern in Modern React
You've probably seen a component like this: it fetches data in an effect, tracks loading and error state, handles pagination, formats dates, filters
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Higher-Order Components: Are They Still Relevant?
If you open a React codebase that's more than a few years old, you'll probably find exports like `export default withRouter(connect(mapState)(withSty
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Render Props vs Custom Hooks: Evolving React Patterns
Before hooks, sharing stateful logic between React components was awkward. You couldn't call a function that "had state" because only class component
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Compound Components Pattern in React
Every component library eventually builds a Tabs component, and the first version usually looks like this: Tabs with an items prop that takes an
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Discriminated Unions for Type-Safe React Props
Look at almost any growing component library and you'll find props types like this: href?: string, onClick?: () => void, isLoading?: boolean, `
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Generic Components in React with TypeScript
Sooner or later you build a component that works with "some kind of item": a list, a dropdown, a table, an autocomplete. The first version usually ty
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TypeScript with React: Typing Props, State, and Events
Most React bugs that TypeScript catches are boring ones: a prop passed as a string instead of a number, a state value that can be null but is used
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Migrating from Create React App to Vite
Create React App was the default way to start a React project for years, but it's now officially deprecated. The React team stopped recommending it i
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Building React Apps with Vite: A Fast Modern Setup
If you've worked on an older React project, you probably remember waiting for the dev server. Starting it took half a minute, and every save took a f
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Image Lazy Loading Techniques for React Apps
Images are usually the heaviest thing on a page. A product grid with 60 thumbnails, a blog index with a hero image per post, or a photo gallery can e
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Web Workers in React: Offloading Heavy Computation
JavaScript in the browser runs on a single main thread, and that thread is also responsible for handling clicks, running React, and painting the scre
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Debouncing and Throttling User Input in React
Some events fire far more often than you need to respond to them. A user typing "react hooks" into a search box fires eleven onChange events. Scrol
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Optimizing Bundle Size in React Applications
Every kilobyte of JavaScript you ship has to be downloaded, parsed, compiled, and executed before your app becomes interactive. On a fast laptop with
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Virtualizing Long Lists with TanStack Virtual
Render 10,000 rows with .map() and React creates 10,000 components, the browser creates tens of thousands of DOM nodes, and the first paint takes s
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Preventing Unnecessary Re-Renders with React.memo
When a component's state changes, React re-renders that component and every component below it, whether their props changed or not. Most of the time
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Profiling React Apps with React DevTools
Most React performance work goes wrong at the first step. Someone notices the app feels slow, guesses which component is to blame, and wraps half the
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Automatic Batching in React 18 and Beyond
You call three state setters in a row inside a fetch callback and your component renders three times. Worse, the first of those renders shows the n
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Concurrent Rendering in React: What Changed and Why
Type into a search box that filters ten thousand rows and, in an older React app, the input freezes. Every keystroke kicks off a render of the whole
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Why Keys Matter When Rendering Lists in React
Every React developer has seen the console warning: "Each child in a list should have a unique key prop." The quick fix is to add key={index}, the
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React Fiber Architecture Explained Simply
Type into a search box that filters a list of 10,000 items in an older React app and you can feel the problem. Each keystroke triggers a render, the
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Understanding the Virtual DOM and Reconciliation
"React is fast because of the virtual DOM" is one of the most repeated lines in frontend development, and it's only half true. The virtual DOM isn't
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Error Boundaries: Gracefully Handling Crashes in React
When a React component throws during rendering and nothing catches it, React unmounts the entire tree. Your users don't see a helpful message. They s
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Suspense for Data Fetching: How It Works Under the Hood
Suspense looks like magic the first time you use it for data. A component reads data as if it were already there, with no isLoading flag and no `
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Code Splitting in React with React.lazy and Suspense
A single-page app usually ships as one big JavaScript file. Every route, every chart library, every rich text editor, and every admin screen gets dow
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Protected Routes and Authentication Flows in React
Every app with accounts eventually needs the same flow. A visitor opens /dashboard, gets sent to the login page, signs in, and lands back on the da
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Nested Routes and Layouts with React Router
Look at almost any dashboard app and you'll see layers. There's an outer shell with a top bar. Inside it, a settings section with its own sidebar. In
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React Router v7: A Complete Beginner's Guide
A React app without a router is a single screen. As soon as you need a home page, a product page, and a settings page that each have their own URL, w
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Client-Side Form Validation Patterns in React
Most form bugs aren't about sending data. They're about telling the user what's wrong at the right time. Show an error the moment someone types the f
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Handling File Uploads in React with Drag and Drop
A plain file input works, but it is not a great experience. Users expect to drag files from their desktop onto the page, see thumbnails before anythi
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Formik vs React Hook Form: A Side-by-Side Comparison
For years, Formik was the default answer to "how do I build forms in React?" It took the tedious parts of controlled forms, like tracking values, tou
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Building Accessible Forms with React Hook Form and Zod
A form can look polished and still be unusable for a large group of people. A screen reader user tabs into an input and hears "edit text" with no ide
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Controlled vs Uncontrolled Components in React Forms
Every form input in React has a value, and something has to own it. Either React holds the value in state and pushes it into the input on every rende
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Derived State in React: Common Mistakes and Better Patterns
A surprising number of React bugs come from the same root cause: storing a value in state that could have been calculated from other values. A filter
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Managing Server State with TanStack Query
Fetching data in React looks simple until you ship it. A useEffect with fetch and two pieces of state works for a demo, then the real questions a
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Recoil vs Jotai: Comparing Atom-Based State Libraries
Recoil introduced many React developers to the idea of atomic state: small, independent pieces of state that components subscribe to individually
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Jotai and Atomic State Management in React
Picture a dashboard where a filter in the sidebar, a chart in the middle, and a summary card in the header all depend on the same few pieces of state
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Zustand: Lightweight State Management for React Apps
Most React apps reach a point where useState and props stop being enough. A cart count in the header, a sidebar toggle shared across layouts, or a
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RTK Query: Data Fetching and Caching Made Simple
If you have ever written a Redux slice just to fetch a list of posts, you know the routine: a status field, an error field, a thunk, three reduce
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Getting Started with Redux Toolkit in React
Redux has a reputation for boilerplate: action type constants, action creators, switch statements, spread operators nested four levels deep, and a se
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Context API vs Redux: Which One Should You Use?
"Do I still need Redux now that we have Context?" is one of the most common questions in React. You'll find confident answers on both sides: Context
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Avoiding Prop Drilling with the React Context API
Your App component knows who the logged-in user is. The avatar that needs that user lives inside Header, inside Navbar, inside UserMenu. So y
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Lifting State Up: Sharing Data Between Sibling Components
You've built a search input and a results list as two separate components. Each works on its own, but now the list needs to know what the user typed.
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React Compiler Explained: Automatic Memoization Without the Boilerplate
Every React developer has written code like this: a component re-renders too often, so you wrap a computed value in useMemo, wrap a handler in `use
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useActionState and Form Actions in Modern React
A typical React form submission used to need a surprising amount of code. You'd call preventDefault(), read every field from state, set an `isSubmi
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useOptimistic: Building Instant-Feeling UIs in React
You click a heart icon and nothing happens for 400 milliseconds. Then it fills in. The request succeeded, but the app felt sluggish, and some users c
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useSyncExternalStore: Subscribing to External Data Sources Safely
Not all state lives in React. The browser knows whether you're online, how wide the window is, and what's in localStorage. A WebSocket client holds
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useId: Generating Stable IDs for Accessible Components
Accessible HTML runs on IDs. A <label> points at its input with htmlFor, an input points at its error message with aria-describedby, and a tab
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useTransition and useDeferredValue for Smoother UIs
You type a letter into a search box and the whole page freezes for half a second. The input lags behind your fingers, characters appear in bursts, an
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Exploring the React use() Hook for Promises and Context
For years, reading async data in a React component meant the same ritual: a useState for the data, another for loading, another for errors, and a `
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useLayoutEffect vs useEffect: Timing Differences That Matter
You build a tooltip that measures its own height and flips above the trigger if there isn't room below. It works, but every time it opens, there's a
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The Rules of Hooks Explained with Real-World Examples
"Rendered more hooks than during the previous render." If you've seen that error, you've broken one of the rules of hooks. It usually happens in code
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Building Your Own Custom Hooks in React
You write a component that tracks window width with useState, useEffect, and a resize listener. A week later you need the same thing in another c
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useMemo and useCallback: When Memoization Actually Helps
Open almost any React codebase and you'll find useMemo and useCallback wrapped around things that don't need them: a string concatenation, an inl
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Mastering useRef: Beyond Accessing DOM Elements
Most developers meet useRef as "the hook for focusing an input." You attach it to an element, call ref.current.focus(), and move on. That's a fin
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Why Your useEffect Runs Twice in React Strict Mode
You add a console.log inside useEffect, open the browser, and see it printed twice. Your API request shows up twice in the Network tab. An analyt
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A Practical Guide to useEffect and Its Dependency Array
useEffect is the hook people get wrong most often, and the dependency array is usually where it goes wrong. Leave a value out and your effect works
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useState vs useReducer: Choosing the Right State Hook
Every React component that remembers something uses either useState or useReducer. Most of the time useState is the obvious pick: a boolean for
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Understanding the React Component Lifecycle in the Hooks Era
If you learned React with class components, you probably remember the lifecycle diagram: componentDidMount, componentDidUpdate, `componentWillUnm
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Micro-Frontends with React: Breaking Down Monoliths into Scalable Components
The micro-frontend architecture allows large applications to be broken down into smaller, more manageable parts. It’s an effective way to manage
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