React Js Developer Quiz

1️⃣ Let's start simple—what is React.js mainly used for?

A) Backend development B) Database management C) Building user interfaces D) Writing server-side scripts

2️⃣ What is the main feature of React.js?

A) Two-way data binding B) Virtual DOM C) Synchronous rendering D) Direct database access

3️⃣ What is a React component?

A) A JavaScript function or class that returns UI B) A database table C) A CSS file D) A server-side API

4️⃣ What are functional components in React?

A) Components without a constructor B) Components written as functions C) Components without styles D) Components using old class syntax

5️⃣ What is the purpose of JSX in React?

A) To write HTML inside JavaScript B) To define CSS styles C) To call backend APIs D) To encrypt JavaScript files

6️⃣ Which of these is a React hook?

A) useState B) componentWillMount C) shouldComponentUpdate D) renderComponent

7️⃣ What does useState() do in React?

A) Handles API calls B) Creates a state variable in a functional component C) Runs after component mounts D) Fetches data from a database

8️⃣ What does useEffect() do?

A) Renders a component B) Handles side effects like API calls C) Modifies CSS dynamically D) Stops React from re-rendering

9️⃣ What is lifting state up in React?

A) Moving state to a parent component B) Increasing state value automatically C) Storing state in Redux D) Resetting state on button click

🔟 How do you pass data from parent to child component in React?

A) Using Redux B) Using props C) Using context D) Using useEffect

1️⃣1️⃣ What is React Router used for?

A) Managing navigation in a React app B) Storing global state C) Handling form validation D) Optimizing performance

1️⃣2️⃣ What is the default method to handle forms in React?

A) Redux B) Controlled components C) Uncontrolled components D) localStorage

1️⃣3️⃣ What is the context API in React used for?

A) Managing global state without props drilling B) Fetching data from an API C) Encrypting user data D) Styling components

1️⃣4️⃣ What does memoization do in React?

A) Caches component output to improve performance B) Saves user input locally C) Encrypts component state D) Stores data in session storage

1️⃣5️⃣ Which hook prevents unnecessary re-renders?

A) useState B) useMemo C) useEffect D) useContext

1️⃣6️⃣ What is React Fragment (<></>) used for?

A) Grouping elements without adding an extra DOM node B) Adding a new HTML tag C) Creating modals D) Storing state

1️⃣7️⃣ What is server-side rendering (SSR) in React?

A) Running React on the backend before sending HTML to the client B) Fetching data from a server C) Running React on a mobile app D) Encrypting server data

1️⃣8️⃣ What is the difference between controlled and uncontrolled components?

A) Controlled components store state in React B) Uncontrolled components handle API calls C) Uncontrolled components are more secure D) Controlled components cannot have events

1️⃣9️⃣ What is Redux used for?

A) Managing global state B) Fetching API data C) Creating components D) Handling CSS animations

2️⃣0️⃣ What is the Redux store?

A) A central state container B) A database C) A frontend library D) A component

2️⃣1️⃣ What is the Redux action?

A) An object that describes a state change B) A function that renders components C) A way to fetch data D) A JavaScript event

2️⃣2️⃣ What is lazy loading in React?

A) Loading components only when needed B) Delaying API requests C) Reducing page size D) Optimizing CSS

2️⃣3️⃣ Which React hook is used for performance optimization?

A) useCallback B) useState C) useEffect D) useContext

2️⃣4️⃣ What is the default behavior of setState() in React?

A) Merges new and old state B) Replaces the entire state C) Deletes previous state D) Runs synchronously

2️⃣5️⃣ What does React.StrictMode do?

A) Highlights potential issues in the application B) Prevents component rendering C) Blocks API calls D) Increases component speed

React Js Developer Quiz

🌟 Job Ready - 100% Scorers