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ReactJS Interview Questions You Should Ask While Interviewing Developers

Published: April 5, 2018
ReactJS Interview Questions You Should Ask While Interviewing Developers

Constantly evolving software development demands frameworks and tools that offers ultimate efficiency. An amazing open source JavaScript front end UI library that is meant to create interactive and reusable UI components for web as well as mobile applications is available as ReactJS. Often considered as “A JavaScript Library for Building User Interfaces”, its features are quite innovative in optimizing time and efficiency.

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The Competency of ReactJS

ReactJS makes use of a special syntax called JSX, which is a feature that enables developers to mix JavaScript and HTML. Although designers comfortable with CSS and HTML might be reluctant in using it, it is the smartest and most convenient way for the designers and the developers to collaborate. Overall, ReactJS has made its way to the list as one of the most trending technologies for front-end development.

You Need a Professional Who is an Expert in ReactJS

Are you planning to develop a web application or a mobile app using React? If so, it will be a best to hire a React developer from the start. You should follow a few guidelines to help you hire the right developer for your ReactJS-based projects.

The skillset of a ReactJS developer is quite similar to that of a front-end developer. Below is a list of expertise that is typically expected from any ReactJS developer that knows their field:

  • Highly skilled in front-end frameworks like Bootstrap or Foundation
  • Quite familiar with CSS preprocessors like SASS and LESS
  • Expertise in fundamentals of HTML, CSS and JavaScript
  • Knowledge of other JavaScript frameworks like Angular JS and Ember
  • Very familiar with JavaScript libraries like jQuery or Backbone

To simplify the interviewing process, consider preparing a short list of ReactJS interview questions that will cover vital aspects of the technology, especially keyed to the applications you are preparing to create. For instance:

What is Flux and its Key Components in ReactJS?

While working with React, Facebook internally makes use of the architecture named Flux, which is neither a framework nor a library. It is the application architecture used to build JavaScript applications for Facebook and is based on a unidirectional data flow. From small widgets to huge applications designed with Flux, React has handled everything that has been thrown at it. In addition, you can start using it without a lot of new code beyond React.

Individual components include:


These facilitate the passing of data to the Dispatcher. Whenever new data enters the system either through a person who interacts with the application or through a web API call, the data is packaged into the action. These helper methods not only create the action object, but also pass the action to the dispatcher.


The dispatcher is required to provide a simple, synchronous iteration through the callbacks, invoking each in turn. After the entire set of dependencies has been fulfilled, the original callback then continues to execute. In brief, a dispatcher receives actions and broadcasts payloads to the registered callbacks.


In Flux, these stores are required to manage the application state for a particular domain within your application. Thus, these stores manage the data, data retrieval methods and dispatcher callbacks. These are the containers for application state and logic that have callbacks registered to the dispatcher.

Controller views

These are the React components that listen to the change events and retrieve the application state from the stores. Thereafter, they pass that data down to the child components through props.

What is the Difference between Flux and MVC?

Have you ever been to web application development? If yes, then you definitely have some experience with MVC architecture. Various technologies including ASP.NET, PHP, Ruby on Rails, and JavaScript frameworks as well as libraries is a great architecture for web applications. Talking about Flux, a new application architecture was introduced by Facebook in 2014 in order to overcome the limitations of MVC architecture. While Flux follows the concept of unidirectional data flow, MVC includes bidirectional data flow. Undeniably, unidirectional data flow reduces the probability of unpredicted data mutations.

What are the Events That Occur in ReactJS Components Lifecycle?

The lifecycle methods in ReactJS are important to ensure that the developers can produce a quality application and they can plan what and how to do at various phases of UI interfaces. The react component goes through different phases that include –


Initialization allows the react component to prepare itself for the upcoming tough journey, by setting up initial states and default props.


After the component is prepared with its basic needs, state and props, it is then mounted in the browser DOM. Mounting phase provides with the hook methods prior to and post mounting the components.


Updating phase includes the updation of the component either by sending new props or by updating the state.


In Unmounting phase, the component gets unmounted from the DOM.

Tell us about the Difference between Stateful and Stateless Components in ReactJS

Are you looking for the software developers with the great understanding of React? Just do not miss to ask this question. The stateless react components never change the state. Apart from this, they do not even access the data that is related to past, present or future changes of a state. On the contrary, the Stateful component changes its state and stores information about the changes made in past, present or future.

Are You Aware of the Difference Between Props and State?

As you know that there is a very thin line between the two, it is important to ask this question during the interview. Where the states are mutable, slower and used as places where the data comes from, the props are exactly different. These are used to pass the data from the top-level components.

Define Higher Order Components

It is not possible for a candidate to implement a basic HOC pattern, as it will take more time than typically allotted for an interview. Instead, you can ask him or her to definition HOC. Higher order components are the React components that include other components.

Asking these questions to the candidate will cover all the aspects of the technology. Isn’t it a great idea to have a list of questions related to the basic aspects of React handy? Thus, these can be typically asked while hiring a remote React developer.

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