Top React JS Interview 2025 Quiz Quiz

Test your knowledge of key React JS concepts with this quiz featuring common interview questions for 2025. Enhance your skills in JSX, components, hooks, state management, and more essential topics for React developers.

1. React Overview

   What is the main purpose of React JS in web development?

   1. To manage server databases
   2. To design CSS-only layouts
   3. To create backend APIs
   4. To build user interfaces using a component-based approach

2. JSX Understanding

   In React, what does JSX allow you to do within your JavaScript code?

   1. Declare variables globally
   2. Style components with CSS
   3. Write HTML elements directly
   4. Run database queries

3. Virtual DOM Concept

   How does the Virtual DOM contribute to improved performance in React applications?

   1. By updating only changed elements instead of the entire DOM
   2. By storing images in the cloud
   3. By running code on the server
   4. By compressing JavaScript files

4. Components in React

   What is a component in React, and how is it typically used?

   1. A type of CSS file
   2. A function to query databases
   3. A building block that returns React elements for the UI
   4. A page of server-side code

5. Props Definition

   How are 'props' used in a React component example?

   1. To execute server requests
   2. To change the color of text
   3. To manage global styles
   4. To pass data from parent to child components

6. State Usage

   What does the 'state' of a React component represent?

   1. A list of installed libraries
   2. The user’s browser location
   3. The component’s current data or situation
   4. The current CSS styles

7. useEffect Purpose

   When would you typically use the useEffect Hook in a React functional component?

   1. To log errors to the console
   2. To declare a new component
   3. To create a new stylesheet
   4. To perform side effects like data fetching after rendering

8. Redux Basics

   What is Redux mainly used for in a React application?

   1. Managing the application’s state centrally
   2. Styling components with CSS
   3. Building navigation menus
   4. Optimizing image loading

9. Keys in Lists

   Why should each list item in a React array have a unique 'key' prop?

   1. To style items with unique colors
   2. To increase the app’s security
   3. To help React identify which items have changed, are added, or are removed
   4. To enable server communication

10. Controlled Components

    What makes a form input a controlled component in React?

    1. Its value is managed by React state
    2. It is styled using a CSS file
    3. It loads data from an API automatically
    4. It connects directly to a database