Top 50 React Interview Questions and Answers For 2021
Let us start by taking a look at some of the most frequently asked React Interview Questions:
1. Differentiate between Real DOM and Virtual DOM. 2. What is React? 3. What are the features of React? 4. List some of the major advantages of React. 5. What are the limitations of React? 6. What is JSX? 7. What do you understand by Virtual DOM? Explain its working. 8. Why can’t browsers read JSX? 9. How different is React’s ES6 syntax when compared to ES5? 10. How is React different from Angular?
As of today, there are about 1,000 contributors on Github. Unique features like Virtual DOM and reusable components grab the attention of front end developers. Despite being just a library for ‘View’ in MVC (Model-View-Controller), it’s giving strong competition to full-blown frameworks like Angular, Meteor, Vue, etc. Check out the belo2w graph which shows the trend of popular JS frameworks:
React Interview Questions
So, here are the Top 50 React Interview Questions and Answers which are most likely to be asked by the interviewer. For your ease of access, I have categorized the React interview questions namely:
General React – React Interview Questions
1. Differentiate between Real DOM and Virtual DOM.
Real DOM vs Virtual DOM
1. It updates slow.
1. It updates faster.
2. Can directly update HTML.
2. Can’t directly update HTML.
3. Creates a new DOM if element updates.
3. Updates the JSX if element updates.
4. DOM manipulation is very expensive.
4. DOM manipulation is very easy.
5. Too much of memory wastage.
5. No memory wastage.
2. What is React?
It follows the component based approach which helps in building reusable UI components.
It is used for developing complex and interactive web and mobile UI.
Even though it was open-sourced only in 2015, it has one of the largest communities supporting it.
3. What are the features of React?
Major features of React are listed below:
It uses the virtual DOM instead of the real DOM.
It uses server-side rendering.
It follows uni-directional data flow or data binding.
4. List some of the major advantages of React.
Some of the major advantages of React are:
It increases the application’s performance
It can be conveniently used on the client as well as server side
Because of JSX, code’s readability increases
React is easy to integrate with other frameworks like Meteor, Angular, etc
Using React, writing UI test cases become extremely easy
5. What are the limitations of React?
Limitations of React are listed below:
React is just a library, not a full-blown framework
Its library is very large and takes time to understand
It can be little difficult for the novice programmers to understand
Coding gets complex as it uses inline templating and JSX
React Interview Questions and Answers 2021 | Edureka
6. What is JSX?
Hello World from Edureka!!
7. What do you understand by Virtual DOM? Explain its working.
Whenever any underlying data changes, the entire UI is re-rendered in Virtual DOM representation.
Then the difference between the previous DOM representation and the new one is calculated.
Once the calculations are done, the real DOM will be updated with only the things that have actually changed.
8. Why can’t browsers read JSX?
9. How different is React’s ES6 syntax when compared to ES5?
Syntax has changed from ES5 to ES6 in following aspects:
require vs import // ES5 var React = require(‘react’); // ES6 import React from ‘react’;
11. “In React, everything is a component.” Explain.
Components are the building blocks of a React application’s UI. These components split up the entire UI into small independent and reusable pieces. Then it renders each of these components independent of each other without affecting the rest of the UI.
12. What is the purpose of render() in React.
Each React component must have a render() mandatorily. It returns a single React element which is the representation of the native DOM component. If more than one HTML element needs to be rendered, then they must be grouped together inside one enclosing tag such as