ReactJS interview questions

Posted on  

March 15, 2022

Published by: Codemonk

ReactJS is one of the efficient, flexible, and most scalable frameworks for web and application development. The ReactJS occupies approximately 68.9 percent of the software development market. Therefore, companies are hiring more ReactJs developers to salvage their technology needs.

However, there is a certain complexity in the interview-based selection of ReactJS developers. In the entire Javascript library, ReactJS is the highly used framework in the digital market. In addition, an individual might find it difficult as the ReactJS development method is evolving each day with new technologies and tools. 

Importance of ReactJS in web and application development:

Today ReactJS is a highly important aspect of digital development. It allows the data in a reusable format with supportive UI technology. Moreover, it gives a high scalability ratio to the large web application, which can transform the data without page reloading. The ultimate goal of ReactJS development programming is to develop a high-quality application through an agile, flexible, scalable, and simplified platform. 

Top 23 React.Js Interview Questions You Must Prepare in 2022:

Here is a listing of some of the top questions which an individual can prepare for better performance in an interview. This question covers the complete functions and properties of the ReactJS on the practical platform.

Basic Level Interview Questions

There are some basic-level interview questions that the hiring organization might ask the ReactJS developer. All these questions are regarding ReactJS basic knowledge and properties. Some of the basic questions are listed below, check them out:

Question 1: What are the main features of ReactJS?

There are several features of ReactJS that make this development of JavaScript scalable and flexible for a wide range of websites and applications.
The main features of the ReactJS program are:

  • It uses virtual DOM rather than real DOM.
  • In ReactJS, server-side rendering is used.
  • The ReactJS follows the data binding or unidirectional data flow.

Question 2: Can web browsers read JSX directly?

Web browsers cannot read the JSX indirectly as the browser engines cannot read and understand the program. It does not have any inherent implementation in the browser or search engines. Various effective transpilers convert the JSX into readable and supportive JavaScript code that can be easily run on multiple browsers and search engines.

Question 3: What exactly does JSX mean?

JSX is the shorthand program of JavaScript XML. ReactJS uses this file to utilize the accurate expressiveness in the HTML program. In the HTML program, JavaScript is used along with the HTML, just like template syntax. Therefore, it simplifies the file to understand the core idea and eventually boosts the application and website performance to a higher ratio.

Question 4: What is an event in React?

React events are the activities that are triggered for the user activity. React has its handling tools which are known as react events. These events are very much like the DOM events. The react events are termed synthetic events, which are cross-browsing agents of the native search engine. 

  • Instead of lowercase react events are Camelcase.
  • By JSX, an event handler is a valid event instead of strings.

Question 5: How to develop an event in ReactJS?

Creating an event in the ReactJS needs some specific command with the appropriate rules. Here is the description:

function Component(){





// Some more responses to the event


return (


<button onEvent={doSomething}></button>



Here, ‘e’ is the synthetic event. 

ReactJS- Questions on Components 

ReactJS has some components whose functioning and properties are important to know for an individual. Here are the interview questions that cover the components and their functional platform. Let's have a look:

Question 1: What are functional and class components in ReactJS?

The functional component in the ReactJS is the plain JavaScript which accepts the props like an argument and converts and returns them in the form of React element. The class component requires a basic extension with the React program and inside class components. In such cases, the Hooks can be used as the functional components.

Question 2: How does ReactJS differ from Angular?

Angular is the JavaScript framework that is built for application development using Typescript. ReactJS is a JavaScript library that develops applications using JSX. Angular is used to build the complex application of enterprise-grade and single-page format. In addition, ReactJS is used to develop the application by building the UI components by variable data of applications. 

Question 3: Explain the concept of virtual DOM with respect to ReactJS?

The virtual DOM is a unique programming concept where the virtual and ideal representation through UI is stored in the memory. This representation then undergoes syncing with the virtual or real DOM library, ReactDOM. This synchronized process is called reconciliation, where the react undergoes deep observation of pattern and component variation in the program. 

Question 4: Side effects in React compounds?

There are four major working side effects of the React components which provide issues in the data flow program:

  • React sets up the page title in an imperative manner.
  • Work with the set timers.
  • Work with the measurable quantities of DOM like width, height, and position of elements.
  • Produces logging messages to other connected consoles and associated services.

Question 5: What rule should one follow to use React Hooks?

Hooks are the JavaScript functions that react to build a robust application program. Here are the two basic rules to follow while using the React Hooks:

  • Call the hooks only with the React components, not the regular JavaScript program.
  • At the program's top-level, call hooks are not inside the loops and are nested.

Question 6: What is Redux?

Redux is the latest and most trending library of front-end development. Using Redux in the application development program makes it simple for testing and develops them with a high ratio of flexibility to runinvariant digital environments with constant consistency. In addition, Redux is the state container of JavaScript used to manage applications during the development process. 

Question 8: What is Flow?

Flow is the static examining tool of the JavaScript Code. Its development was with Facebook and used effectively in React. It can annotate all the React components, variables, and functions along with the special typing Syntax. Moreover, it provides the exponential privilege to detect errors easily. 


Question 9: What is React Router, and how is it useful?

React router is a powerful routing tool in the library, which uses a simplified API. It helps in adding new flow and screens to theReact programs. It is built on the top of the React program and displays on the browser's web page. It maintains the synchronization of URL and data with a standardized structure. 

Question 10: How is Reactrouting different from conventional routing?

The React routing uses the single HTML page to function with the variant navigation process across different page appearances. The user gets confused through this duping. For example, the history attribute is completely transformed in the React routing, while in the conventional routing, it needs to send the HTTP request to the server. In return, a corresponding HTML page is received where each view corresponds with a new file.


Questions on ReactJS application

Here is a list of questions regarding the application of ReactJS in various development projects of the web of variant platforms. These questions can help the ReactJS developer to flaunt their practical knowledge during the interview. Let’s discuss:

Question 1: Limitations of ReactJS/ Areas where ReactJS can't be used?

There are certain limitations of ReactJS and areas where the ReactJS application cannot be used. Here is the description:

  • React is a library and not a framework.
  • The use of JSX and inline templating makes the coding complex.
  • Novice programmers cannot use ReactJS

Question 2: Give some real-life examples based on ReactJS?

Here are some of the real-life examples of ReactJS listed:

  • Implementing the calculator in the IOS program is through ReactJS.
  • BMI calculator is a ReactJS hook
  • Snapshot a photo gallery to search.

Question 3: Explain the entire life cycle of the React components?

  • Initial rendering phase: Components start their journey by making their way to DOM.
  • Updating phase: After entering the DOM, the component goes through the potential update and re-rendering process. In this stage, the prop or state variation occurs in the component. 
  • Unmounting phase: The final phase where the components are removed from the DOM after destruction.

ReactJS interview questions: Styling  

ReactJS works with various styling tools and components. Below is the description regarding the question that can help you in the interview explain the functionality and properties of the styling method and tools of ReactJS in the development project. Let’s start: 

Question 1: Can a React component be styled? If yes, then how?

The react component accepts the styling with the props. Therefore, it needs the prop-based styling tools, CSS-JS, which act as the bridge with styling the component with variable features and functions. All these numerous styling props are reusable in many ways.


Question 2: How do you style React components?

Here is the description of style react components:

  • Inline styling: The components can undergo styling directly through the inline attribute of JavaScript.
  • JavaScript Object: Styling with JavaScript object creating the separate JavaScript with desired properties.
  • CSS stylesheet: Style the React component by developing the CSS file with various styles and features.

ReactJS Interview Questions: Miscellaneous 

Some miscellaneous questions about the ReactJS development process, application, properties, functionality, and other associated aspects are asked in an interview. Below is the listed description of some such questions that will help you impressively explain them. So, let’s have a look:

Question 1: What is meant by a higher-order component in ReactJS?

The high-order component is the advanced technology to reuse the component's logic with specific patterns. They are not a part of React API and provide a new component taking the old one. 

Question 2: How does the React Hook differ from classes?

Hooks do not work inside the class but provide a platform to use the classes. Hooks are the functions that connect the Reactstate with the lifestyle features from the functional components. 

Question 3: How to design the automated redirect functionality post-login in ReactJS?

The automated redirects functionality post-login in React JS functions by grouping the bunch of hooks rather than following the same redirection route.

Question 4: Explain redux flow structure?

Redux follows a unidirectional data flow with one-way binding data. When the user interacts with the application, an action is dispatched in return. Here in this state, the root reducer function appears with the dispatched action. 

Do you want to crack the ReactJS interview?

Here are some important and basic questions useful for the ReactJS interview as the technologies are evolving each day; hence, individuals need to update themselves continuously. All these questions thoroughly help in an interview to answer with complete clarity and knowledge. In the efficient ReactJSdevelopers’ companies invest a high amount of interest and capital. Most of the highly paid ReactJS developers are paid around $20 to $38 per hour.


ReactJS is the upgrading technology that is highly efficient with better digital possibilities in the future. People preparing for the ReactJS developing program can go through the above questions to get a better and more descriptive idea regarding the interview and prepare with good and descriptive answers. Coming opportunities can turn much better with better preparation.

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