A List of the 25 Most Crucial Interview Questions for ReactJS


ReactJS has been the go-to technology for developers for several years, thanks to its promising future potential. At Works, we’ve compiled a helpful list of 25 top ReactJS questions and answers that are commonly asked during interviews. These questions cover a wide range of topics, from basic to advanced, and can assist candidates in preparing for interviews.

How Can I Best Prepare for My Upcoming ReactJS Interview?

It’s a common question that arises among developers at all levels, whether they’re just starting out or are experienced ReactJS professionals.

To give you a general idea of preparing for a ReactJS interview, we’ll go over the key topics that should be covered during the interview.

  • Document Object Model (DOM) and using DOM in
  • The React Lifecycle methods.
  • JSX.
  • Manipulatable and non-manipulatable components and Pure components.
  • Redux.
  • HOC.
  • Correctly Referencing State.
  • Hooks.
  • Forms.
  • Courses
  • ES6 (For Those Who Are Unfamiliar).

While it’s important to keep the above-mentioned topics in mind, it’s equally crucial for developers to conduct comprehensive research on all relevant areas, practice coding questions that could be asked during the interview, and rehearse for the actual interview.

Entry-Level ReactJS Interview Questions and Answers

Put Simply, What is React?

Facebook launched React in 2013 as a JavaScript library that simplifies the development of user interfaces by relying on reusable components. Its modular architecture makes creating front-end UIs an easier endeavour.

Currently, it’s used to build user interfaces for both desktop programs and smartphones.

What are the Capabilities of ReactJS?

Here are some of the core features provided by ReactJS:

  1. Virtual DOM enables faster UI rendering.
  2. ReactJS follows a unidirectional data flow.
  3. Developers can easily create new components with ReactJS thanks to its JSX syntax.

What is DOM in Virtual Reality?

By utilizing the ReactDOM module, a virtual Document Object Model (DOM) is generated and stored in memory. This virtual DOM ensures that the structural interpretation of a UI stays synchronized with the actual DOM representation.

The DOM is emulated through a tree of nodes that provide details about various elements, attributes, and other constituents. Using ReactJS’ render function, the node tree is created and updated automatically based on modifications made to the core data model.

What is JSX?

To construct its UI, ReactJS employs JSX, which is a syntax extension of JavaScript. It allows coders to include both HTML and JavaScript in a single file, making the pages easier to read and improving the performance of the application.

What Makes ReactJS So Popular?

ReactJS has been extensively embraced by developers due to its numerous advantages.

  1. ReactJS offers reusable modules that can be employed in diverse projects.
  2. The use of a virtual DOM enables swift rendering of the UI.
  3. React simplifies the process of testing.
  4. Scaling up with React is an effortless task.
  5. ReactJS enhances the usability and legibility of the application for the end user.
  6. It’s worth noting that React can be used on both the client and the server side.

Is JSX Supported by Browsers?

Browsers cannot read JSX files directly, as they are only capable of interpreting JavaScript object files. Therefore, for a browser to understand a JSX file, it must be transformed into JavaScript, which is compatible with browsers.

After being converted into JavaScript objects, JSX files must be provided to the browser using a tool such as Babel.

What are the disadvantages of utilizing ReactJS?

  1. Inadequate data logging capabilities.
  2. Due to the frequent updates to the React libraries, it becomes imperative to frequently refresh one’s knowledge of the fundamentals.
  3. Learning JSX might pose a challenge as it combines both JavaScript and ReactJS.

What is Meant by “Component-Based Architecture”?

React’s component-centric design allows for faster rendering of smaller individual components, thus enhancing the overall rendering speed of the user interface.

What is the Role of States in React?

Due to the fact that states are regarded as source data that impact the actions and rendering of components, they hold paramount importance in React.

Moreover, they allow for the creation of dynamic and interactive UI components.

For Experienced Programmers, What are Some Relevant Questions to Ask During a ReactJS Job Interview?

For experienced developers like yourself, here are some significant and intricate ReactJS interview questions to be ready for. You can hire such developers from Works.

What is Meant by “React Hook”?

React 16.8 brought in ‘hooks,’ which enable developers to utilize React’s features and state without having to work with classes. They derive their name from their link to components, which provide them with access to React’s lifecycle and state.

Furthermore, they do not cause any breaking changes as they are compatible with earlier versions.

What is the Extent of Making Changes in React?

React utilizes reconciliation as the procedure for executing DOM manipulation. The chosen algorithm defines the manner in which the components are rendered.

An Overview of Higher-Order Components (HOC) in React.

React’s ability to reuse component logic is strengthened through the utilization of Higher Order Components, which are an advanced technique. Moreover, it is possible to enhance the efficiency of the application and its overall functionality by permitting all React components to have a shared set of behaviours. You can read more about improving efficiency in our related blog post here.

Here are some scenarios where it can be employed:

  1. Usage for implementing component-level styling.
  2. Conditional rendering of components is achievable.
  3. Bootstrapping is employed for collecting data.

What are the Different Stages in the Component Life Cycle of React?

The component cycle of React consists of three distinct stages:

Initial Sketch

The initial phase involves the addition of the UI element to the Document Object Model (DOM).


Upon completion, the altered and re-rendered component is dispatched to the DOM.


Finally, the component is removed from the DOM and destroyed.

How Does React Stand Out in Comparison to Angular?

Parameter React Angular
Author Facebook(Meta) Google
DOM Virtual DOM Real DOM
Architecture View Layer Of MVC Complete MVC
RENDERING Server Side Client Side

What are Controlled and Uncontrolled Elements, and what are their Roles in React?

Inactive components lack the ability to modify their state, whereas active ones have this capability. The main module handles data management. Using props and corresponding changes in callbacks, the stored value can be accessed.

A reference to a DOM is obtained using ref when a persistent or present value is needed, but this duty is undertaken by uncontrolled components.

Primitive Building Blocks: An In-depth Look

Since they do not require any assembly, these independent components can be authored quickly and efficiently. They can also be utilized in lieu of components comprising a render() method, leading to a more structured code and improved application performance.

Advanced ReactJS Interview Questions

Our compilation of top ReactJS interview questions 2023 is a definitive resource for accomplished ReactJS developers to ace any interview.

Elucidate the Distinctions Between CreateElement and CloneElement

As the name suggests, CloneElement duplicates an element and transmits its information to new props.

CreateElement, in contrast, is a construct in which JSX is compiled.

What Problems are Addressed by React API Context 16?

Incorporating the Context API makes it feasible to minimize the necessity of passing props through the component tree by allowing for data sharing among components. Examples of data that may be beneficial to share between parent and child components include UI style and user information.

What is the Purpose of React Portal and React Fragment?

Portals may be used to render child components in the DOM when the child component is situated outside the parent component’s DOM node hierarchy.

React Fragment, conversely, permits the grouping of child components in a way that doesn’t add nodes to the DOM. This is possible because React is solely concerned with producing a single object from the render.

First off, let’s establish the meaning of the PropType Library.

PropType is a React export library that enables type checking for incoming data components. This promotes self-documentation of components and lowers the potential for errors.

What is the Process of the React Component Lifecycle?


This process takes place prior to rendering, encompassing both the client and server sides.


On the client side, this is executed once the initial render is finished.


When the parent class provides the props and no other renders are present, this method is called.


On every occasion, it is the task of the Boolean function to determine whether a return of true or false is needed. A return of true is issued if the component necessitates an update, otherwise a return of false is provided.


If the render function isn’t called, this function is triggered.


Once the render function is called, this function is triggered.


Once a DOM component is removed, this method is called.

What is the Meaning of the Term “Redux”?

An open-source JavaScript library, Redux, assists in managing application state and creating user interfaces. React components are capable of accessing data from the Redux store, submitting actions to the store, and altering the contained data.

If Asked, “What is Prop Drilling?”

The method of transmitting data or state from a parent component to a child component with multiple levels of inheritance is referred to as prop drilling. A sequence of intervening elements is employed to communicate data and state to their ultimate destination.

Explain how React Fiber Functions.

With React 16 comes React Fiber, which is a reimagination of the core algorithm of React that ensures the preservation of React’s incremental rendering for the virtual DOM. Subsequently, this enhances the performance and responsiveness of user interface animations, gestures, and other features.

Moreover, it boosts productivity by prioritising updates based on the requirements of the user.

Utilize Pre-verified Property Types

The following are the available built-in prop types that can be used straightaway.

PropTypes.func Property Type

  1. PropTypes.node Property Type
  2. PropTypes.number Property Type
  3. PropTypes.string Property Type
  4. PropTypes.bool Property Type


ReactJS is the preferred technology for front-end programming, and IT companies have a significant demand for ReactJS developers. The language empowers the development of mobile and desktop applications, ensuring customers an uninterrupted user experience.

IT organizations have a thorough screening process to determine the eligibility of candidates for open positions. Among the final and most critical phases of the recruitment process is the technical interview, in which ReactJS knowledge can be assessed through various questions.

Our list of the best interview questions and answers can assist you in preparing for your next ReactJS interview.

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