Top React Interview Questions to Ask Before Hiring a ReactJS Developer

When it comes to hiring ReactJS developers, ask any hiring manager what their biggest pet peeve is, and out comes the answer in a chorus: “Asking the right React interview questions“ That’s not the entire picture, though. Some other challenges that ground-level hiring managers face on a routine basis include:

• Longer technology hiring cycles: The hiring process is excruciatingly long now. It doesn’t follow a linear pattern where you call candidates for an interview, conduct a coding test, and send off an appointment letter. Today, candidates have to pass multiple levels of tests, such as undergoing a preliminary screening, passing through a technical and an aptitude test, undergoing a ‘cultural fitness’ (with the company), acing the primary interview, and finally, engaging in a salary negotiation. Naturally, the hiring cycle has extended to a couple of months.
• An expensive talent market: To make things more complicated, reportedly, over  11,025 companies use React in their tech stacks, including the likes of Uber, Airbnb, and Facebook. This means that industry stalwarts are also eyeing the same talent and competing for the pool of resources as well as skills within a tight, competitive market. Automatically, this makes the talent market more expensive.
• Validating candidates’ skills: Once the candidates are shortlisted, the next task becomes ensuring that they stand tall in their resume achievements, qualifications, and other React JS developer skills. This becomes a major pain point for hiring managers.

In this blog, we will look at some of the most important React interview questions that will enable hiring managers to find the best Reactjs developer. To make the hiring streamlined, we have categorized the list of questions into three parts:

1. React.js interview questions for entry-level or junior developers
2. React dev interview questions for mid-level developers
3. React coding interview questions for senior Reactjs developers

Let’s jump right in.

Top ReactJS Interview Questions to Ask While Hiring 

Let’s start by understanding the top React interview questions. 

1. React JS Interview Questions 2022 for Entry-level or Junior Developers

Junior (basic) developers come with the least experience and by extension, demand the lowest salary. That said, junior developers must have the following basic skills:

• Basic HTML, JavaScript, and CSS skills
• Good working knowledge of ReactJS 
• The ability to learn on the job, follow instructions, and receive feedback
• The ability to think like a programmer

Let’s begin by taking a look at some of the most important junior React developer interview questions. 

Q1. Write a sample of a simple HTML document., Please include header information and page content.

Why asking this question is crucial for hiring managers: This question allows hiring managers to gauge the developer’s basic HTML skills.

Key points an interviewee should include in their response:

• The fact that HTML documents are different
• HTML documents generally follow a basic structure, which includes the head and body
• The various sections are marked with tags such as DOCTYPE, meta, body, HTML, head, title, h1, p

Q2. What is the end goal for the following code?

render() { let className = ‘menu’; if (this.props.isActive) { className += ‘ menu-active’; } return <span className={className}>Menu</span> }

Why asking this question is crucial for hiring managers: This is one of the key react coding interview questions that help hiring managers to assess the candidate’s ability to use CSS with React.

Key points an interviewee should include in their response: 

• The fact that the code adds a CSS class to a component
• This is done by passing a string as the className prop
• The class is based on the component props/state, which is common with ReactJS

Q3.  What is a JavaScript callback function? Provide an example of the same. 

Why asking this question is crucial for hiring managers: This question will help hiring managers to assess the candidate’s basic JavaScript skills.

Key points an interviewee should include in their response:

• A callback function refers to a function that is called after another function is completed
• It is passed to another function as an argument
• It is invoked once an operation is complete

Q4. What is ReactJS?

Why asking this question is crucial for hiring managers: This question will help hiring managers to assess the candidate’s foundational ReactJS knowledge.

Key points an interviewee should include in their response:

• ReactJS refers to an open-source JavaScript library, also known as a framework
• It helps create dynamic single-page applications
• These applications typically need less coding than doing everything in JavaScript.
• Overview knowledge of react native

Q5. What is ReactJS and how does it compare to other JavaScript frameworks?

Why asking this question is crucial for hiring managers: This React JS interview question will help hiring managers to assess the candidate’s foundational ReactJS knowledge. Hiring managers will get an inside perspective of what React is and how it works within the JavaScript ecosystem.

Key points an interviewee should include in their response:

• React is basically an open-source JavaScript library, which is maintained by Facebook
• It helps design dynamic and interactive user interfaces and components for web as well as mobile applications
• It is often seen as “View” in the “Model-View-Controller” (MVC) architecture.
• As compared to Angular, it is a relatively smaller framework
• It can be easily integrated with other libraries and applications
• It is not as opinionated about an application‘s architecture (when compared to other frameworks such as Angular and Vue.js)
• It is a strong community that supports multiple tools and packages

Q6. How do you intend to learn a new JavaScript library?

Why asking this question is crucial for hiring managers: This question will help hiring managers to understand the candidate’s ability to learn on the job and extract knowledge from hands-on experience. 

Key points an interviewee should include in their response:

• Web development is ever-changing, and hence, developers must be able to learn constantly
• The candidate must clearly define the kind of information they need and how they plan to find the same (for instance, looking at online tutorials or documentation)

Q7.  Elaborate on when you received real-time feedback on a programming task. What were your biggest learnings as a programmer?

Why asking this question is crucial for hiring managers: Such junior react developer interview questions help hiring managers to understand whether the candidate can follow instructions, receive feedback constructively, and work on bettering themselves.

Key points an interviewee should include in their response: 

• This is an example of an open-ended question, where the candidate must be able to demonstrate how they are able to accept, analyze, and act on feedback

Q8. At [company name], we often face [XYZ] issues. What do you think is a possible solution for the same?

Why asking this question is crucial for hiring managers: This is one of the react interview coding questions that help hiring managers to know whether the candidate is able to think and work like a programmer in the truest sense of the term.

Key points an interviewee should include in their response:

• The candidate must be able to describe how they will solve the problem with their day-to-day working style
• Remember that there’s no perfect or correct answer
• The idea is to understand how the candidate will approach a problem and work on it

2. React Interview Questions 2022 for Mid-Level Developers

If you are looking to hire mid-level or intermediate developers, be on the lookout for the following skills in your react JS developer job description:

• They should have at least 3 to 4 years of experience
• They should be able to execute routine tasks with greater skills and efficiency
• They should be able to mentor junior developers

Moving on, let’s look at React JS interview questions for intermediate developers.

Q1. What are the advantages and limitations of using ReactJS?

Why asking this question is crucial for hiring managers: This question will help hiring managers to understand the candidate’s ReactJS knowledge.

Key points an interviewee should include in their response:

Q2. What is Virtual DOM, and why is it important?

Why asking this question is crucial for hiring managers: This question will help hiring managers to assess the candidate’s expert-level ReactJS knowledge.

Key points an interviewee should include in their response:

• As one of the key concepts in React, the candidate must be able to explain the main problems with DOM manipulation and how virtual DOM can help

Q3. What is JSX, and how does it relate to ReactJS? Provide an example.

Why asking this question is crucial for hiring managers: This question will help hiring managers to assess the candidate’s expert-level ReactJS knowledge.

Key points an interviewee should include in their response:

• JSX (JavaScript XML) empowers developers to include XML syntax in the JavaScript, make code more intuitive, and help developers to read code more easily
• The React library understands that both JavaScript and HTML are strongly related; having them in isolation across different HTML and JavaScript files can make things more confusing
• While using JSX with React is a compulsion, it makes sense to use it together

Q4. What do components refer to in React?

Why asking this question is crucial for hiring managers: This is one of the key advanced coding questions for react interview that help hiring managers to assess the candidate’s expert-level ReactJS knowledge.

Key points an interviewee should include in their response:

• ReactJS is component-based; these ‘components’ double up as the building blocks of a ReactJS application
• It helps split the UI into multiple separate and reusable pieces

Q5. What does render() do?

Why asking this question is crucial for hiring managers: This question will help hiring managers to assess the candidate’s expert-level ReactJS knowledge.

Key points an interviewee should include in their response:

• Every React component comprises a render() function
• Render() returns only one React element, which is representative of a native DOM component
• For render() to work, multiple HTML elements must be grouped inside one tag, for instance, <group>

Q6. What kind of knowledge do you have about the Flux architecture pattern?

Why asking this question is crucial for hiring managers: This question will help hiring managers to understand the candidate’s experience with Flux architecture.

Key points an interviewee should include in their response:

• Instead of using MVC, many ReactJS applications use Flux architecture
• The biggest feature is that it enforces unidirectional data flow
• The three major parts of a flux application include:

1.Stores

2. Dispatcher

3. View (React components)

Q7. What kind of knowledge do you have about the Redux library?

Why asking this question is crucial for hiring managers: This react developer interview question will help hiring managers to understand the candidate’s experience with the various libraries they use. In this case, it will help hiring managers to understand how they can use Redux to create testable applications.

Key points an interviewee should include in their response:

• Redux refers to a state management library, also known as React
• Key characteristics of a Redux library include the following:

1. It acts as a single source of truth

2. The state is read-only

3. The changes can be made with Pure functions

Q8. What kind of testing tools would you use for unit testing in a ReactJS application?

Why asking this question is crucial for hiring managers: This question will help hiring managers to understand the candidate’s knowledge of unit testing UI components and other react developer tools.

Key points an interviewee should include in their response:

• Unit testing refers to a technique that helps test isolated segments of code and ensure that they are functioning properly
• Key testing tools for ReactJS applications include React, unit, Enzyme, Jest, Skin-deep, react-testing-library, Unexpected-react, etc.

3. React Advanced Interview Questions for Senior Reactjs Developers

When it comes to asking advanced React interview questions, you need to have a separate list of questions that can assess the skills and expertise of experienced ReactJS developers. After all, you want these developers to be able to build a best-in-class application for your ReactJS development company, right?

Some of the most common skills experienced developers must possess include:

• Extensive ReactJS knowledge as well as other JavaScript frameworks and libraries (such as Node JS)
• The ability to design, maintain, and upgrade secure and stable apps
• The ability to use Flux architecture and engage in asynchronous programming
• The ability to drive efficient programming, write clean code, and engage in debugging
• The ability to drive end-to-end and unit testing
• The ability to demonstrate leadership skills, communication skills, and mentor less experienced developers

Q1. What kind of React patterns are you aware of? 

Why asking this question is crucial for hiring managers: This question will help hiring managers to the candidate’s knowledge of React patterns and app architecture.

Key points an interviewee should include in their response:

• There are a lot of patterns for React, such as High Order Component (HOC), Render Prop, Function as children, and Container and Presentational components

Q2. Have you worked with React 16 Context API? In your experience, what kind of issues has it solved?

Why asking this question is crucial for hiring managers: This react interview question advanced helps hiring managers to understand how well the developer knows about React Context API.

Key points an interviewee should include in their response:

• React Context API helps pass data through the component tree
• You don’t need to pass props down manually at every level
• It is used to share global data (such as user, theme, etc.) between child components

Q3. Have you worked on code splitting with React? Please describe how a bundle is split into smaller chunks.

Why asking this question is crucial for hiring managers: This question will help hiring managers to understand the candidate’s level of understanding relating to Webpack bundling and React.lazy or React Loadable.

Key points an interviewee should include in their response:

• You can use React tools to prevent large bundle sizes
• You can use React Loadable due to its simplicity or use React Lazy as an alternative
• React Loadable signifies a small library for wrapping components into bundles
• It offers useful features such as placeholders for “Loading” and “Error” components and flash delay
• In the chance of a component being wrapped, Webpack will move it into a new bundle

Q4.  If you had the freedom to use any and all kinds of tools to build a rock-solid application, what would you use?

Why asking this question is crucial for hiring managers: Such react interview questions for senior developers help hiring managers to understand the candidate’s design skills. It also helps them to gauge the candidate’s own ability to understand requirements for development.

Key points an interviewee should include in their response:

• The candidate must talk about the kind of developer they are and how they like to code
• They should also be able to clearly define their requirements 
• They should be able to provide a list of required libraries and tools, which indicates how well they have understood the task

Q5. How active are you in the ReactJS community?

Why asking this question is crucial for hiring managers: This question will help hiring managers to understand how passionate a developer is about web development.

Key points an interviewee should include in their response:

• The interviewee must talk about their contribution towards the community and speak about their open source developments as clearly as possible.

Q6. Talk about your experience of fixing an error in a web application.

Why asking this question is crucial for hiring managers: This question will help hiring managers to gauge how the interviewee is able to approach debugs and errors. Plus, they will also get an overview of how the candidate is able to break down a problem into logical and practical segments.

Key points an interviewee should include in their response:

• The candidate must be able to answer the following questions:

1. How they approached the problem

2. What kind of debugging tools they used

3. What they learned from this experience

Q7. What do you primarily look for when assessing another team member’s code?

Why asking this question is crucial for hiring managers: Such react advanced interview questions help hiring managers to analyze how well the interviewee is able to mentor others regarding react web development and provide insights into their leadership skills. Hiring managers will also be able to assess the interviewee’s attention to detail, skills level, and wide-ranging knowledge of mistakes beginner developers demonstrate.

Key points an interviewee should include in their response:

• The interviewee must touch upon topics such as code functionality, style conventions, security flaws, readability, simplicity, regulatory demands, and resource optimization

How to Avoid the Hassle of Hiring the Ideal ReactJS Developer?

If you are looking to hire the right candidate for your ReactJS project, consider Uplers. At Uplers, you’ll find it easier to recruit qualified and pre-screened ReactJS developers. You can get access to a ready pool of talented developers without doing a ton of legwork yourself. Here’s how our vetting process works:

According to our own estimates, over 10,000 talents apply every month, but only 3.5% make it to the network.

• We review applications against our minimum criteria and the candidate’s professional journey and conduct holistic background checks.
• Our AI-powered communication assessment tests a candidate’s reading, writing, pronunciation, clarity, fluency, and speed of speech.
• Next, we conduct a scientifically designed aptitude test to check the candidate’s reasoning and problem-solving ability.
• We set up the toughest and most advanced technical assessments to vet the candidate’s capabilities. This role-based test helps filter the top 10% of talent.
• Finally, our Talent Acquisition experts conduct a video interview to understand the candidate’s preferences and expectations to do the right matchmaking.

In Summary

As a hiring manager, consider this list to be your Holy Grail when it comes to coding questions for React interviews. To wrap up, in this blog, we have listed React interview questions for junior developers, React interview questions for senior developers, and React interview questions for intermediate developers.

Whether you want to find the best talent or create a world-class app, the first step is getting the right people on your team. They are and will be your company’s biggest asset so take the time and effort to do it right–starting with this list.