Top ReactJS Interview Questions and Answers
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In this article, we’ll cover some popular ReactJS interview questions and answers to help you prepare and get ready for your upcoming technical interview.
Here’s what we’ll discuss in this article:
- Most Popular ReactJS Interview Questions and Answers
- FAQs on ReactJS Interview Questions
Most Popular ReactJs Interview Questions and Answers
This section will look at some popular ReactJS interview questions, mostly asked at Java developer and SQL developer interviews.
Q1. What are some advantages of using ReactJS?
This is a popular ReactJs interview question asked in Java interviews. ReactJs offers a host of advantages to front-end developers. They include:
- The ReactJs framework is highly SEO friendly, offering front-end developers to make tweaks to improve website performance by optimizing the application/web page.
- React allows for reusable components as it incorporates a component-based architecture model. Components are nothing but bits of code that can be reused, and React allows developers to re-use and modify code whenever and wherever necessary with ease.
- React uses a virtual DOM, improving the efficiency of applications created.
- React offers a vast list of libraries and tools, allowing developers impressive depth and flexibility.
Q2. What is JSX in React?
Q3. What do you understand about Virtual DOM?
The Virtual DOM in ReactJs is when a virtual representation of the real DOM is placed inside the memory. The virtual DOM is then synced with the real or actual DOM by the ReactDOM library.
Q4. What are the different lifecycle phases in ReactJS?
This is yet another frequently asked ReactJS interview question. Lifecycle phases in ReactJS allow developers to alter the phase of a given lifecycle. The different lifecycle phases that components or blocks of code go through include:
Q5. What are the different Lifecycle methods in the Mounting lifecycle phase?
The lifecycle methods under the Mounting lifecycle phase are:
Q6. What are the lifecycle methods in the Updating phase?
The methods under the Updating lifecycle phase are:
Q7. What are the lifecycle methods in the Unmounting phase?
There is just one lifecycle method associated with the Unmounting Phase — componentWIllUnmount
Q8. Can browsers directly read JSX?
Q9. What are the steps involved in creating the React app?
The steps involved in creating the React app include:
- Install the create-react-app package
- Install a text editor, and you’re ready to go.
Q10. What do you understand about an event in React?
An event is an action performed by the user or computer. Any action that involves pressing a key, mouse clicks, or typing out sentences, classify as events. React events are in camelCase, unlike lowercase in HTML.
Q11. What do you understand about a component in React?
A component in react is a block of code that serves as a building block of the React application. Components are part of the UI and split user interfaces into multiple reusable parts, processing each part individually.
Q12. What are the two types of components in React?
Knowing the answer to this ReactJS interview question is essential. The two types of components in React are - Functional Components and Class Components.
Q13. What do you understand about Synthetic events in React?
Synthetic events in React are events that combine native events of different browsers into a single API, thereby ensuring consistency.
Q14. How do you achieve the traversal of lists in React?
This is a common ReactJS interview question asked at Java interviews. In React, the traversal of lists can be accomplished through the map() function.
Q15. Why do we need to use keys in React lists?
Keys are extremely helpful in identifying lists and changes that have been made to items in lists. They also signify which components in the library need to be re-rendered based on the corresponding updates and prevent other items from unnecessarily being re-rendered.
FAQs on ReactJs Interview Questions
Q1. What is ReactJs, and what is it used for?
Q2. When can you expect to be asked ReactJS interview questions?
Q3. Do you need to have in-depth knowledge of ReactJS while appearing for Java technical interviews?
Q4. What are some concepts around which React interview questions are asked in technical interviews?
Some common concepts around which you’re asked React interview questions at tech interviews are lifecycle methods, events in React, lists, forms, functions, components, and commands used in React.
Q5. What is the use of the Arrow function in React?
The Arrow function helps to write short-form versions of functions in React, saving time and assisting developers in avoiding errors.
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