Comprehensive list of React job interview topics

Core React

• JSX syntax and expressions

• React Components

  • Functional vs Class components

• Props and State

• Component Lifecycle (Class & Hooks)

• Conditional Rendering

• Lists and Keys

• Event Handling

• Forms and Controlled Components

• Lifting State Up

React Hooks (Must-Know)

• useState

• useEffect (dependencies, cleanup, multiple effects)

• useRef

• useContext

• useReducer

• Custom Hooks

• Rules of Hooks

Advanced Concepts

• Context API

• Higher-Order Components (HOCs)

• Render Props

• React.memo and useMemo

• useCallback

• Reconciliation and Virtual DOM

• Forward Refs

• Error Boundaries

• Portals

• Suspense and Lazy Loading

State Management

• Lifting state vs global state

• Context API with useReducer

• Redux (or alternatives like Zustand, Jotai, Recoil)

  • Actions, Reducers, Store

  • Middleware (e.g., Thunk, Saga)

  • DevTools and debugging

• Component-local state vs app-wide state

Routing

• React Router (v6)

  • Nested Routes

  • BrowserRouter, Routes, Route, Link, useNavigation

  • Dynamic Routing

  • Route Protection (Private Routes)

   

Performance Optimization

• Code splitting & Lazy loading (React.lazy & Suspense)

• React.memo

• useMemo and useCallback

• Windowing (e.g., react-window)

• Avoiding unnecessary re-renders

 Testing

• Unit Testing with Jest

• React Testing Library (RTL)

  • Rendering components

  • Mocking props, state, API

  • Firing events and asserting DOM

• Snapshot testing

• End-to-end testing (e.g., Cypress or Playwright)

Dev Tools & Ecosystem

• React Developer Tools

• Linting & Formatting (ESLint, Prettier)

• Build tools: Vite, Webpack, Create React App

• TypeScript with React (optional but highly valued)

API Integration

• Fetching data (fetch, Axios)

• useEffect with API calls

• Handling loading, error, success states

• Optimistic UI updates

• React Query / SWR (if applicable)

 Miscellaneous

• Environment variables

• File structure and scalable project organization

• Reusable component design

• Accessibility (ARIA roles, keyboard navigation)

• SEO in React (basic SSR/Meta handling)

Common Coding Challenges

• Building:

  • To-do app / Form with validation

  • Modal, Accordion, Tabs

  • Pagination / Infinite scroll

  • Search with debounce

• Handling:

  • Nested state updates

  • Conditional rendering logic

  • Controlled vs uncontrolled inputs