Top 10 React JS Interview Questions and Answers Of 20225 min read

Hey Developers, In this Post we you will Top 10 React JS Questions, If you are a React Developer or Learning React Js for Development then you should Know these React Questions. And In this post I will be Also Answering all the Questions.

Table Of Contents:

• What is React?
• Why use React?
• 10 React Questions With Solution
• Conclusion

React is a free and open source front-end JavaScript library for building user interfaces based on UI components. It is maintained by Meta and a community of individual and corporate developers.

Why use React?

• Flexibility: React is a Flexible JavaScript Framework, Once you have Learned React you can Run It Anywhere or In Any System. React JS is Library Not a Framework. React was created with one goal in mind: to create components for web applications. A React component can be anything in your web app like a button, text, label, or grid.
• React’s Great Experience: React JS Has Very Good Developer Experience, Once You Learn React You fall in love it because it has Grids, Components, And it Developer Friendly & Machine Independent. JSX is a special HTML-like syntax that converts API calls from React and ultimately renders the HTML.
• React Developer Community: React JS Has a Large Developer Community Working on React & Creating Awesome Web Apps & Websites. React’s NPM (Node Package Manager) has a Millions Of Users.
• Facebook Supports React: The Biggest Feature of React is that React JS was Created by Facebook In Year 2013.
• High performance: React Offers a High & Fast User Experience, Because of Virtual DOM which Makes the Websites Faster by Not Reloading when Moved To Another Page this is Called Hot Reloading In React. Unlike Other Websites It Reloads When Moved to Any Other Page.

Most Asked React JS Questions (With Solution)

1. What is JSX?

JSX is a syntax extension of JavaScript It is used with React to describe what the user interface should look like. It Looks Similar to a HTML Code.

2. Can web browsers read JSX directly?

No Web Browsers Cannot Read JSX Directly Because JSX is not Regular JavaScript Component And They Only Read Regular Objects.

In Order to Render the JSX File Directly from the Browser Then It should be converted To Regular JavaScript Object. For this We Use Babel.

3. What is the virtual DOM?

DOM Stands for Document Object Model, The DOM shows an HTML Document with a Logical Tree Structure. And Each Tree Ends in a Node, and each Node contains objects. React keeps a lightweight representation of the real DOM in memory, called the virtual DOM. When the state of an object changes, the virtual DOM only modifies that object in the real DOM, rather than updating all objects.

4. How do you create a React app?

To Create a React App:

Step 1: Download & Install Node JS On your Computer, We are Installing This Because npm (Node Package Manager) to Install React Library.

Step 2: After you Have Installed Node Js In your Computer Then, Run create-react-app package to Create a New React React App.

Step 3: Install Any Code Editor Like Vs Code And Start run npm start to run your react app.

5. What are Components in React?

Components are self-contained and reusable pieces of code. They serve the same purpose as JavaScript functions, but work individually and return HTML. Components are of two types, class components and functional components. In this tutorial, we will focus on functional components.

6. How do you create an event in React?

To Create Events In react, Write the Following Code:

import React from 'react';
  
function App() {
  function eventHandler(){
    console.log('Mr Programmer Website is Awesome');
  }
  
  
  return (
    <div className='App'>
      <h1>This is www.mrprogrammer.in</h1>
      <button onClick={eventHandler}>Click to Know Website</button>
    </div>
  );
}
  
export default App;

7. How do you write comments in React?

We can Write Comments In React By Using the double forward-slash // or the asterisk format /* */.

For Example:

import React, { Component } from 'react';

// This is a comment

class App extends Component {

	/* Comment
	In React JS*/
	render() {
		return (
			<div>
				<h4>Mr Programmer is Best!</h4>
			</div>
		);
	}
}

export default App;

8. How is React JS different from Angular JS?

The Following are the Major Differences Between React JS & Angular JS:

9. What is the use of render() in React?

render() Function is Required For Each Component. This returns HTML Code which is display in the component

If you want to render more than one element, all of the elements must be inside one parent tag like <div>, <form>.

10. What is a state in React?

A state is a built-in React Object that is used to store data or information about any component. The state Component can be Changed if required and then it re-renders it.

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Tanmay Sinha

Founder & CEO at Mr Programmer

Founder & CEO of MrProgrammer.in | I help Learning Freaks to Step into the World of Programming and Our Mission is to Provide High Quality and Valuable Content to Our Users!

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