12 React Interview Questions and Answers

If you’re among the web and app developers who use React, you’ll probably need to be able to explain your knowledge to employers to be considered for a job. In this article, we’ll show you how to get a positive reaction from hiring managers by mastering these React interview questions and answers.

Before you meet with a hiring manager, here’s something to consider: You wouldn’t expect a user interface to perform its best if it’s not well structured, properly coded, and optimized. To perform your best, take some time to familiarize yourself with these 12 React interview questions. Then, develop thoughtful answers and practice them in advance.

React Interview Questions and Answers

1. Tell Me What You Know About React.
2. What Are the Advantages and Limitations of React?
3. Describe What Keys Are and How They’re Used in React.
4. What Is JSX and How Is It Used in React?
5. What Is the Virtual DOM in React?
6. What Is Redux in React?
7. What Do You Know About React Hooks?
8. What Are Custom Hooks and Why Do Developers Use Them?
9. Walk Me Through How to Create a List in React
10. Show Me How You Would Create a Form in React.
11. What Is React Native and How Does It Differ From React JS?
12. What Is Flexbox and How Does It Work in React Native?

Basic React Interview Questions

The first three React interview questions will focus on the basics, including an overview of React, its advantages and disadvantages, and keys.

Question #1: Tell Me What You Know About React.

If you’re asked to provide an overview of your knowledge of React, discuss the key points that make React unique among app-building tools.

Your response should include:

• A definition of React.
• What it does.
• Why developers use it.

How You Could Answer

“React is a free and open-source front-end JavaScript library. It was developed by Facebook and open-sourced at JSConf US in 2013. Developers use it to build interactive user interfaces (UI) and web applications with reusable components. React is also declarative, which means that it specifies what a program should accomplish without listing commands and steps.”

Question #2: What Are the Advantages and Limitations of React?

Be prepared for React interview questions that ask you to discuss the pros and cons of using React and how it compares to other app development tools.

Here’s what you should include in your answer:

• Characteristics and features that make React unique.
• Potential drawbacks of using React.

How You Could Answer

“The key advantages to using React are:

• A faster app development process.
• Flexible module structure in comparison to other front-end frameworks.
• High-performance server-side rendering for faster app run-time.
• It’s easy to use with only basic JS knowledge.
• It allows developers to save time by reusing existing components.

React also has some limitations. For example, it:

• Only works with UI and nothing else.
• Contains only pre-written code and is not a framework.
• Doesn’t support SEO. Therefore, developers need to optimize applications for SEO separately.”

Question #3: Describe What Keys Are and How They’re Used in React.

Developers often use keys in React to render components such as lists and tables. If an employer asks you to discuss how to use keys, include the following details in your answer:

• How they’re used for element lists.
• How they differentiate elements.

How You Could Answer

“In React, keys are special string attributes used when creating element lists to identify which elements get added, updated, and removed. They also help React differentiate elements from each other by assigning them unique IDs.”

React JS Interview Questions

These next three React interview questions will focus on JavaScript XML (JSX), the Virtual DOM, and the use of Redux.

Question #4: What Is JSX and How Is It Used in React?

Since developers frequently utilize JSX, get ready to answer React interview questions about the following:

• The purpose of JSX in React.
• How JSX helps simplify app development.

How You Could Answer

“JSX is an acronym for JavaScript XML. It’s a syntax extension of JS that allows developers to write HTML in JS. This makes it easier for developers to create React components and detect errors than using JS on its own.

With JSX, developers can place HTML elements in the Document Object Model (DOM) and convert HTML tags to React elements. As a result, JSX eliminates the need for createElement() or appendChild() and similar methods used in JS.”

Question #5: What Is the Virtual DOM in React?

The Virtual DOM is a core feature of React. When formulating your answer, include the following details:

• A brief overview of the Virtual DOM.
• What the Virtual DOM does.
• How it simplifies UI updates.

How You Could Answer

“The Virtual DOM—a virtual representation of the real DOM—is a JavaScript concept used by React to track changes made to web applications and optimize their performance. Nearly all applications rely on the Virtual DOM to update the user interface.

When rendering JSX elements, corresponding updates to the real DOM can be time-consuming. To make the process more efficient, the Virtual DOM constructs a new tree of React elements that represent the updated state of the application. It then compares the new tree with the previous one and identifies which changes need to be made to the original DOM.”

Question #6: What Is Redux in React?

If you’re experienced with React, you’ve likely worked with Redux, the JS library used in app development. Show employers that you have a full understanding of how Redux works by including these details in your answer:

• A definition of Redux.
• How it helps developers manage the state of applications.
• How data flows through the Flux architecture.

How You Could Answer

“Redux is a state management JavaScript library used to create and update user interfaces in React. It helps React developers manage the state of applications in a predictable and centralized way. It also uses unidirectional data flow, which means that all app data follows the same one-way binding pattern known as the Flux architecture.

In the Flux architecture, state changes are defined as actions. Actions are sent to dispatchers where they handle state changes. Actions are then sent to stores that hold onto the data until the next state change occurs. Redux also allows time-travel debugging, so developers can step forward or backward through the state of an application.”

React Hooks Interview Questions

The next two React interview questions will focus on the basics of built-in hooks and how to use custom hooks in React.

Question #7: What Do You Know About React Hooks?

Hooks are a fundamental part of React and are widely used by developers. Be sure to include the following information when discussing React hooks:

• What React hooks are and how they work.
• How hooks make it easier to work with React features.
• Common types of React hooks.

How You Could Answer

“Hooks are built-in functions that allow developers to use all React features without having to write class components. With React hooks, developers can use state and lifecycle methods within existing components.

Here are some examples of the hooks I’ve worked with:

• useState Hook allows developers to State variables in function components.
• useEffect Hook is used to perform side effects in function components, such as fetching API data.
• useRef Hook lets developers create references to values between renders and store mutable values that don’t re-render during updates.
• useCallback Hook returns memorized versions of callback functions.
• useMemo Hook returns memoized values and lets developers cache results of calculations between renders.”

Question #8: What Are Custom Hooks and Why Do Developers Use Them?

Employers may ask you to explain how custom hooks are used in React. Create your answer by including these details:

• A description of custom hooks.
• How custom hooks work.
• The benefits of using custom hooks in React.

How You Could Answer

“Custom hooks are reusable functions that use other built-in hooks such as useState or useEffect. Developers often use them to add unique functions to React applications. Due to their reusability, developers don’t have to write recurring code across several components using the same stateful logic. Additionally, custom hooks help:

• Reduce the time it takes to write code.
• Make cleaner code.
• Enhance code render speed.
• Allow for easier testability.”

React Coding Interview Questions

The next two React interview questions focus on basic list and form coding.

Question #9: Walk Me Through How to Create a List in React.

There will likely come a time during your interview when an employer will ask you to demonstrate how to create a list in React. This is a great opportunity for you to show employers that you know your stuff.

When creating your answer:

• Briefly describe how lists are created in React.
• Provide an example of how to write the code for a list.

How You Could Answer

“React lists are created much the same way as JavaScript lists. I would start by using the map() function and structure the code as follows:

const examples = [‘Example 1’, Example 2’, ‘Example 3’];

const listOfExamples = () => {
const listItems = examples.map((example) =>
<li key={example}>
</li>
);
return (
<ul>{listItems}</ul>
);

}”

Question #10: Show Me How You Would Create a Form in React.

Forms are often used in React to collect user input, data, and validations. They include login pages, registration forms, search bars, and surveys.

Make sure your answer includes the following:

• A brief overview of how forms are created in React.
• An example of a coded form.

How You Could Answer

“Creating forms in React involves handling input states and changes, and validating the input. To begin the process, you can use either a class or a function. In this example, I’m going to use a function. The code should read as follows:

function FormOne() {

return (

<form>

<label>Full Name:

<input type="text" />

</label>

</form>

)

}”

React Native Interview Questions

These last two React interview questions will help you differentiate between React Native and React JS and explain how Flexbox works.

Question #11: What Is React Native and How Does It Differ From React JS?

Like React JS, React Native is JS-based. However, it’s very different from React JS. Your answer should demonstrate your knowledge of React Native and compare it to React JS with:

• A definition of React Native.
• A description of the key differences between React Native and React JS.

How You Could Answer

“React Native is an open-source mobile app development framework developed by Meta. Developers use it to create applications for iOS, Android, Android TV, macOS, and tvOS. While React Native is based on the React JS library, its applications are designed exclusively for mobile devices, not web browsers.

While both React Native and React JS are JavaScript-based frameworks, they have many key differences. For example, React Native:

• Doesn’t use a DOM like React JS does.
• Uses a style sheet language called “Flexbox,” which only applies to mobile app development.
• Comes with mobile-specific components such as ScrollView, ListView, and TextInput, which don’t come with React JS.
• Runs natively on mobile devices, which offers better mobile app performance than React JS.”

Question #12: What Is Flexbox and How Does It Work in React Native?

Flexbox is the standard style sheet language of React Native. Show employers your proficiency in Flexbox by including the following information in your answer:

• An overview of Flexbox.
• How developers use Flexbox.

How You Could Answer

“Flexbox is a dynamic and responsive layout system used in React Native to easily organize and align components (reusable bits of code) within containers (a parent element of components). When working with Flexbox, developers can:

• Create layouts that adapt to different devices and screen sizes.
• Specify how much space components should occupy.
• Determine how components should be positioned in relation to other components in a container.”

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