React Js Interview Questions and Answers

To begin with, React JS is an open-source JavaScript library that uses a declarative paradigm for efficiently building user interfaces. In addition, it is useful for creating modular user interfaces and it promotes the development of reusable UI components that display dynamic data.

Significant Features of React JS

React JS uses a JSX or JavaScript Syntax Extension which is a combination of HTML and JavaScript. This JavaScript Extension helps in making the code easy and understandable. React JS commits a virtual DOM that is an exact copy of the real DOM. The whole virtual DOM is updated first and finds the difference between the real DOM and Virtual DOM whenever there are any modifications made. Many institutes provide React JS Training in Noida and one can enroll in them to start a career in React JS. Apart from these, here are some of the significant features of React JS.

  • One-way Data Binding – This refers to a unidirectional data flow from top to bottom. That is from the parent components to the child components. The child component cannot transfer its properties to the parent component but it can have communication with the parent components.
  • Performance – React JS ensures optimum performance as it uses a virtual DOM and updates only the modified parts. In addition, DOM executes in memory and allows users to create separate components which makes the DOM run faster.
  • Extension – React JS comes with many extensions that are useful for creating full-fledged UI applications. In addition, these extensions are useful for mobile app development. They also help in providing server-side rendering. React comes with extensions like Flux, Redux, React Native, etc.
  • Components – This software solution follows a component-based architecture and it distributes the web page into multiple components. Each component in it is a part of the UI design which has its own logic and design as shown in the below image.
  • Simplicity – Being a component-based architecture, react is very simple and easy to use. In addition, its code is also reusable and a combination of HTML and JavaScript. Furthermore, this makes the code easy to understand and debug.

What are the Benefits of Using React JS?

React is an easy-to-use and powerful library of reusable codes. It allows developers to create user interfaces (UI) for websites, mobile apps, and web applications. In addition, it helps in recycling the components multiple times. This recycling of components saves developers time and reduces their time-to-market. Furthermore, it also facilitates rapid updates to their application’s look and feel. React JS is highly fast, simple, and easy to use. This JavaScript library is capable of building separate components that make up the larger UI. Using it helps websites and apps load faster without requiring the user to reload the page. There are many React JS Training Institute in Delhi and one can enroll in them to start a career in React JS. Apart from these, given below are some of the significant benefits of using React JS.

  • ReactJS is a highly scalable software tool useful for JavaScript developers.
  • React JS has declarative applications.
  • It comes with JSX and virtual DOM to boost user experiences.
  • This is a social platform with a large community of designers and developers.
  • It lets you build mobile apps using only JavaScript.

React JS Interview Questions and Answers for Freshers

Here are some of the most common interview questions about React JS.

What are the advantages of React?

The advantages of React are as follows.

  • React JS ensures faster rendering.
  • It is very SEO-friendly. 
  • It combines the speed of JavaScript to render web pages
  • React JS makes web pages dynamic and responsive.
  • It is useful for the development of both web and mobile apps.
  • Capable of integrating with other frameworks.

How is Virtual DOM different from the real DOM?

Real DOM wraps the HTML elements in a tree-structured object and represents the document as nodes and objects. On the other hand, virtual DOM is similar to the real DOM but it can’t write and display things on the screen like Real DOM.

What are the four phases of the ReactJS component lifestyle?

The four phases are Initialization, Mounting, Updating, and Unmounting. Initialization is the first stage that constructs components with the provided properties and a default state. The mounting phase involves putting elements into the DOM. The updating phase updates the stage of a component and repaints the application. The last phase unmounting removes the components from the page.

What is the purpose of the render function () in React?

The render () function in React is useful for displaying the specified HTML code inside the specified HTML



React JS is helpful for developing user interfaces that are modular and it encourages the creation of reusable UI components that show dynamic data. It makes use of JSX, or JavaScript Syntax Extension, which combines JavaScript with HTML. React is highly straightforward and simple to use because it has a component-based design. Additionally, it uses reusable HTML and JavaScript code in its creation. Additionally, it aids in the component’s repeated recycling. React JS is really quick, straightforward, and simple to use. Declarative apps are used by React JS. This social network has a sizable developer and design community.

By Pankajsharma

Hi, I’m Pankaj Sharma from Delhi and working as a freelancer educational blogger, photographer, designer, etc.