React JS Quiz – React JS Multiple Choice Questions And Answers

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React JS Quiz – React JS Multiple Choice Questions And Answers: Check this article, and get the information regarding the React.js MCQ. By this React JS Practice Online Quiz, aspirants can test their skills on the React JS Concepts. Go through the React JS Multiple Choice Questions And Answers, and be familiar with the React JS topics. Our team Freshersnow.com had provided all the required information about the React Js MCQ Quiz. Make the perfect use of React JS Quiz, and practice until you are satisfied with your skills, and knowledge.

React JS Quiz – Overview

Practice React Js MCQ Quiz

What is React JS?
a. A framework for building mobile apps
b. A front-end library for building user interfaces
c. A back-end language for server-side development
d. A database management system
Answer: b. A front-end library for building user interfaces

Explanation: React JS is a popular front-end library for building user interfaces. It allows developers to create reusable UI components and efficiently update the UI when data changes, making it a powerful tool for building web applications.

What is JSX in React JS?
a. A syntax extension for JavaScript
b. A programming language
c. A data structure in React
d. A database management system
Answer: a. A syntax extension for JavaScript

Explanation: JSX is a syntax extension for JavaScript that allows developers to write HTML-like syntax in their JavaScript code. This makes it easier to build UI components and enhances the readability of code.

What is the virtual DOM in React JS?
a. A tool for managing database operations
b. A tool for optimizing CSS
c. A tool for optimizing JavaScript code
d. A representation of the actual DOM in memory
Answer: d. A representation of the actual DOM in memory

Explanation: The virtual DOM is a representation of the actual DOM in memory. When changes are made to the UI, React updates the virtual DOM and then efficiently updates the actual DOM based on the changes made.

What is state in React JS?
a. A way to manage data within a component
b. A way to manage routing in a web application
c. A way to manage styling in a web application
d. A way to manage user authentication in a web application
Answer: a. A way to manage data within a component

Explanation: State is a way to manage data within a component in React. It allows developers to store data and update it as needed, making it a powerful tool for building dynamic UIs.

What is a prop in React JS?
a. A way to manage data within a component
b. A way to pass data from a parent component to a child component
c. A way to manage routing in a web application
d. A way to manage user authentication in a web application
Answer: b. A way to pass data from a parent component to a child component

Explanation: Props are a way to pass data from a parent component to a child component in React. This allows developers to create reusable UI components and build complex UIs with ease.

What is a higher-order component in React JS?
a. A component that is rendered at the top of the DOM tree
b. A component that wraps another component and adds functionality
c. A component that is rendered conditionally based on user input
d. A component that is used to manage routing in a web application
Answer: b. A component that wraps another component and adds functionality

Explanation: A higher-order component is a component that wraps another component and adds functionality. This allows developers to reuse code and keep their components simple and focused.

What is Redux in React JS?
a. A framework for building mobile apps
b. A front-end library for building user interfaces
c. A state management tool for managing data in React
d. A database management system
Answer: c. A state management tool for managing data in React

Explanation: Redux is a popular state management tool for managing data in React. It allows developers to store data in a global store and efficiently update the UI when data changes.

What is the difference between props and state in React JS?
a. Props are used to manage data within a component, while state is used to pass data between components.
b. Props are immutable, while state is mutable.
c. Props are passed from parent to child components, while state is only accessible within a component.
d. Props are used for functional components, while state is used for class components.

Answer: c. Props are passed from parent to child components, while state is only accessible within a component.

Explanation: Props are used to pass data from parent to child components, while state is used to manage data within a component. Props are immutable and cannot be modified by the child component, while state is mutable and can be modified within the component.

What is the purpose of the componentDidMount() lifecycle method in React JS?
a. To update the state of a component
b. To render a component to the DOM
c. To perform an action after a component has been rendered to the DOM
d. To perform an action before a component is rendered to the DOM
Answer: c. To perform an action after a component has been rendered to the DOM

Explanation: The componentDidMount() lifecycle method is called after a component has been rendered to the DOM. It is often used to perform an action, such as fetching data from a server or setting up event listeners.

What is the purpose of the shouldComponentUpdate() lifecycle method in React JS?
a. To update the state of a component
b. To render a component to the DOM
c. To determine if a component should be re-rendered
d. To perform an action after a component has been re-rendered
Answer: c. To determine if a component should be re-rendered

Explanation: The shouldComponentUpdate() lifecycle method is called before a component is re-rendered. It is often used to determine if a component should be re-rendered, based on changes to its props or state.

What is the purpose of the componentWillUnmount() lifecycle method in React JS?
a. To update the state of a component
b. To render a component to the DOM
c. To perform an action before a component is removed from the DOM
d. To perform an action after a component has been removed from the DOM
Answer: c. To perform an action before a component is removed from the DOM

Explanation: The componentWillUnmount() lifecycle method is called before a component is removed from the DOM. It is often used to perform cleanup actions, such as removing event listeners or clearing timers.

What is the purpose of the setState() method in React JS?
a. To update the state of a component
b. To render a component to the DOM
c. To pass data from a parent component to a child component
d. To manage user authentication in a web application
Answer: a. To update the state of a component

Explanation: The setState() method is used to update the state of a component in React. It triggers a re-render of the component, allowing changes to be reflected in the UI.

What is the purpose of the render() method in React JS?
a. To update the state of a component
b. To render a component to the DOM
c. To pass data from a parent component to a child component
d. To manage user authentication in a web application
Answer: b. To render a component to the DOM

Explanation: The render() method is used to render a component to the DOM in React. It returns a tree of React elements that will be rendered to the DOM.

What is a React hook?
a. A way to add functionality to a class component
b. A way to manage data within a component
c. A way to reuse stateful logic across components
d. A way to manage routing in a web application
Answer: c. A way to reuse stateful logic across components

Explanation: React hooks are a way to reuse stateful logic across components in functional components. They allow you to use state and other React features without writing a class component.

What is the purpose of the useState() hook in React JS?
a. To update the state of a component
b. To render a component to the DOM
c. To manage data within a component
d. To manage routing in a web application
Answer: c. To manage data within a component

Explanation: The useState() hook is used to manage data within a component in React. It allows you to add state to a functional component, which was previously only possible with class components.

What is the purpose of the useEffect() hook in React JS?
a. To update the state of a component
b. To render a component to the DOM
c. To manage data within a component
d. To perform an action after a component has been rendered to the DOM
Answer: d. To perform an action after a component has been rendered to the DOM

Explanation: The useEffect() hook is used to perform an action after a component has been rendered to the DOM. It allows you to add side effects, such as fetching data or setting up event listeners.

What is a React component?
a. A class that represents a DOM element
b. A function that returns a DOM element
c. An HTML element that is rendered to the DOM
d. A variable that holds data for a React application
Answer: b. A function that returns a DOM element

Explanation: A React component is a function or class that returns a tree of React elements that will be rendered to the DOM.

What is JSX in React JS?
a. A syntax extension for JavaScript that allows you to write HTML-like code
b. A JavaScript library for managing state in React applications
c. A way to add styling to React components
d. A way to handle user input in React applications
Answer: a. A syntax extension for JavaScript that allows you to write HTML-like code

Explanation: JSX is a syntax extension for JavaScript that allows you to write HTML-like code in your React components. It makes it easier to describe the structure of your UI and is often used with tools like Babel to transform the code into standard JavaScript.

What is the purpose of the React Router library in React JS?
a. To manage state in a React application
b. To handle user input in a React application
c. To add styling to React components
d. To manage routing in a web application built with React
Answer: d. To manage routing in a web application built with React

Explanation: The React Router library is used to manage routing in a web application built with React. It allows you to define routes and map them to components, making it easier to build single-page applications.

What is the Virtual DOM in React JS?
a. A representation of the current state of a React component
b. A lightweight version of the DOM used by React to improve performance
c. A way to add styling to React components
d. A way to handle user input in React applications
Answer: b. A lightweight version of the DOM used by React to improve performance

Explanation: The Virtual DOM is a lightweight version of the DOM used by React to improve performance. It allows React to update only the parts of the DOM that have changed, rather than re-rendering the entire tree. This can lead to faster and more efficient rendering in large applications.