1
What is React? Easy
React is a JavaScript library for building user interfaces. It uses a component-based architecture and virtual DOM to efficiently update and render UI components.
2
What is Virtual DOM? Easy
Virtual DOM is a lightweight JavaScript representation of the real DOM. React compares the Virtual DOM with the previous version and updates only changed parts in the real DOM.
3
What are components in React? Easy
Components are reusable UI building blocks. They can be functional components or class components.
4
What is JSX? Easy
JSX is a syntax extension that allows writing HTML-like code inside JavaScript. It gets compiled into React.createElement calls.
5
Difference between Functional and Class components? Easy
Functional components are simpler and use hooks. Class components use lifecycle methods and this keyword.
6
What are React Hooks? Easy
Hooks are functions that let you use state and lifecycle features in functional components.
7
What is useState? Easy
useState is a hook that allows adding state to functional components.
8
What is useEffect? Easy
useEffect is used for handling side effects like API calls, subscriptions, and DOM updates.
9
What are props? Easy
Props are read-only inputs passed from parent to child components.
10
What is lifting state up? Easy
Lifting state up means moving state to the closest common parent so multiple components can share it.
11
What is reconciliation? Medium
Reconciliation is the process React uses to update the DOM efficiently by comparing previous and new virtual DOM trees.
12
What are keys in React? Medium
Keys help React identify which items changed, added, or removed in a list.
13
What is Context API? Medium
Context API allows sharing global state like themes or auth data without prop drilling.
14
What is prop drilling? Medium
Prop drilling is passing props through multiple intermediate components.
15
What is useMemo? Medium
useMemo memoizes computed values to optimize performance.
16
What is useCallback? Medium
useCallback memoizes functions to prevent unnecessary re-renders.
17
What is React.memo? Medium
React.memo prevents unnecessary re-renders of functional components.
18
What is useRef? Medium
useRef creates a mutable reference that persists across renders.
19
What is controlled component? Medium
A controlled component is one where form data is handled by React state.
20
What is uncontrolled component? Medium
Uncontrolled components store their own state internally using refs.
21
What is Redux? Medium
Redux is a predictable state container for managing global application state.
22
Difference between Redux and Context API? Medium
Redux is more powerful for complex state logic and middleware. Context API is simpler and built-in.
23
What is React Router? Medium
React Router is a library for handling routing in React applications.
24
What are higher-order components? Medium
HOCs are functions that take a component and return a new enhanced component.
25
What is lazy loading? Medium
Lazy loading loads components only when needed using React.lazy.
26
What is Suspense? Medium
Suspense allows handling loading states while components are lazily loaded.
27
What are error boundaries? Hard
Error boundaries catch JavaScript errors in component trees.
28
Explain React Fiber. Hard
React Fiber is the reconciliation engine that improves performance by breaking rendering into units of work.
29
What is server-side rendering? Hard
SSR renders React components on the server before sending HTML to the browser.
30
What is hydration? Hard
Hydration attaches event listeners to server-rendered HTML.
31
Explain Concurrent Rendering. Hard
Concurrent Rendering allows React to interrupt and resume rendering work.
32
What is StrictMode? Medium
StrictMode highlights potential problems in development mode.
33
What is code splitting? Medium
Code splitting splits bundle into smaller chunks for better performance.
34
What is tree shaking? Medium
Tree shaking removes unused code during bundling.
35
Explain React lifecycle methods. Medium
Lifecycle methods include mounting, updating, and unmounting phases.
36
Difference between useEffect and useLayoutEffect? Hard
useLayoutEffect runs synchronously after DOM mutations.
37
What is custom hook? Medium
A custom hook is a reusable function using React hooks.
38
How to optimize React app performance? Hard
Use memoization, code splitting, lazy loading, and efficient state updates.
39
What is Portal in React? Hard
Portals allow rendering components outside the root DOM hierarchy.
40
What is reconciliation algorithm? Hard
React uses diffing algorithm to compare trees efficiently.
41
What is React DevTools? Easy
React DevTools is a browser extension for debugging React apps.
42
Explain batching in React. Hard
Batching groups multiple state updates into one re-render.
43
What is useTransition? Hard
useTransition allows marking updates as non-urgent in React 18.
44
What is useDeferredValue? Hard
useDeferredValue defers a value update to improve performance.
45
What are fragments? Easy
Fragments let you group multiple elements without adding extra DOM nodes.
46
What is React.StrictMode used for? Medium
It identifies unsafe lifecycle methods and potential issues.
47
What is reconciliation vs rendering? Hard
Reconciliation compares trees; rendering updates DOM.
48
How does React handle forms? Easy
Using controlled components with state.
49
What is hydration mismatch? Hard
It occurs when server-rendered HTML does not match client rendering.
50
Explain React architecture for enterprise apps. Hard
Use modular architecture, state management, code splitting, lazy loading, and CI/CD pipelines.
📊 Questions Breakdown
🟢 Easy
13
🟡 Medium
22
🔴 Hard
15
🎓 Master React js Training
Join our live classes with expert instructors and hands-on projects.
Enroll Now
Nagmani Solanki
Digital Marketing
Edugators platform is the best place to learn live classes, and live projects by which you can understand easily and have excellent customer service.
Saurabh Arya
Full Stack Developer
It was a very good experience. Edugators and the instructor worked with us through the whole process to ensure we received the best training solution for our needs.
Praveen Madhukar
Web Design
I would definitely recommend taking courses from Edugators. The instructors are very knowledgeable, receptive to questions and willing to go out of the way to help you.
Need To Train Your Corporate Team ?
Customized Corporate Training Programs and Developing Skills For Project Success.
Get Newsletter
Subscibe to our newsletter and we will notify you about the newest updates on Edugators
