Top Ten Reaction Interview Questions to Prepare for in 2022

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March 2, 2022
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1. Distinguish between the Real DOM and the Virtual DOM.

Real Dom

1. It is a sluggish updater.

2. HTML can be updated immediately.

3. If an element is updated, a new DOM is created.

4. DOM manipulation is extremely costly.

5. Excessive memory squandering.

Virtual Dome

1. It is more up-to-date.

2. HTML cannot be updated directly.

3. Updates the JSX when an element is modified.

4. DOM manipulation is quite simple.

5. There is no memory waste.

2. What exactly is React?

React is a JavaScript library for front-end development released by Facebook in 2011.
It takes a component-based approach, which enables the creation of reusable UI components.
It is used to create complex and interactive online and mobile user interfaces.
Even though it was only open-sourced in 2015, it already has one of the largest communities.

3. What characteristics does React have?

The following are the major characteristics of React:
It makes use of the virtual DOM rather than the real DOM.
It takes advantage of client-side rendering.
It adheres to a one-way data flow or data binding.

4. Summarize several of React’s primary advantages.

Several significant advantages of React include the following:

It optimizes the performance of the application.
It is suitable for use on both the client and server sides.
The readability of code improves as a result of JSX.
React integrates well with other frameworks such as Meteor, Angular, and others.

Writing UI test cases becomes really simple when using React.

5. What are React’s limitations?

The following are some of React’s limitations:

React is a library, not a framework.
Its library is enormous and requires time to comprehend.
It may be a little challenging for inexperienced programmers to comprehend.

Coding becomes more complicated as inline templating and JSX are used.

6. What exactly is JSX?

JavaScript XML is abbreviated as JSX.

This is a type of file used by React that combines the expressiveness of JavaScript with a template syntax similar to HTML.

This makes the HTML file extremely readable.

This file adds robustness to applications and improves their performance.

The following is an illustration of JSX:

code:

render(){

return(

<div>

<h1> Hello World from Edureka!!</h1>

</div>

);

}

7. How do you define Virtual DOM?

Justify its operation.

A virtual DOM is a small JavaScript object that is initially nothing more than a duplicate of the real DOM.

It is a node tree that contains the elements, their attributes, and their content in the form of Objects and their characteristics.

The render function in React constructs a node tree from the React components.

It then updates this tree in response to data model mutations induced by various user or system events.

This Virtual DOM is implemented in three straightforward stages.
Whenever the underlying data is modified, the complete UI is re-rendered in Virtual DOM format.
After that, the difference between the previous and new DOM representations is determined.
Once the calculations are complete, the real DOM will be updated to reflect only the changes that occurred.

8. Why are browsers unable to comprehend JSX?

While browsers can read and write JavaScript objects, JSX is not a standard JavaScript object.

Thus, in order for a browser to read JSX, we must first convert it to a JavaScript object using JSX transformers such as Babel and then provide it to the browser.

9. How does React’s ES6 syntax vary from ES5?

The following features of syntax have changed from ES5 to ES6:

require vs import

// ES5

var React = require(‘react’);

// ES6

import React from ‘react’;

2.export vs exports

// ES5

module.exports = Component;

// ES6

export default Component;

3. component and function

// ES5

var MyComponent = React.createClass({

render: function() {

return

<h3>Hello Edureka!</h3>

;

}

});

// ES6

class MyComponent extends React.Component {

render() {

return

<h3>Hello Edureka!</h3>

;

}

4.props

// ES5

var App = React.createClass({

propTypes: { name: React.PropTypes.string },

render: function() {

return

<h3>Hello, {this.props.name}!</h3>

;

}

});

// ES6

class App extends React.Component {

render() {

return

<h3>Hello, {this.props.name}!</h3>

;

}

5. state

// ES5

var App = React.createClass({

getInitialState: function() {

return { name: ‘world’ };

render: function() {

return

<h3>Hello, {this.state.name}!</h3>

;

}

});

// ES6

class App extends React.Component {

constructor() {

super();

this.state = { name: ‘world’ };

}

render() {

return

<h3>Hello, {this.state.name}!</h3>

;

}

11. “Everything in React is a component.”

Explain.

Components are the skeleton of a React application’s user interface.

These components decompose the entire user interface into small, self-contained, and reusable components.

Then it separates each of these components without affecting the remainder of the UI.

12. What is the objective of React’s render() method?

Each React component is required to have a render() method.

It returns a single React element with the native DOM component’s representation.

If more than one HTML element is required to be rendered, they must be contained within a single enclosing tag such as form>, group>, or div>.

This function must remain pure, returning the same value each time it is invoked.

I hope this set of React Interview Questions and Answers aids you in your interview preparation.

Best wishes!

If you’re interested in learning web development and developing innovative user interfaces on your own, check out the Web Development Certification Training from Nearlearn, a reputable online learning firm with a global network of more than 250,000 satisfied learners.

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