Before you start screening and testing your candidates, you should be aware of the React.js basics. Below you will find the list of essential skills which every skilled React.js developer should have. And not only that, we will show you how to test these skills on a scale, so you can pre-screen and vet tens or hundreds of candidates.
Redux is a tool that helps manage the global state of an application. It’s especially useful for large-scale projects where different components need to share data without prop-drilling (passing data through every child component). Without Redux, managing state in complex apps can become chaotic. Redux keeps data organized, predictable, and consistent.
Ask candidates to create a Redux-powered shopping cart with features like adding and removing items.
Example Question:
“Write a reducer function that handles actions for adding products to a cart.”
Create a complete test and generate more similar questions to evaluate skills of your candidates.
React developers frequently use loops and array methods like .map() and .filter() to render lists dynamically within components. If your app displays lists of data (like products or user profiles), understanding loops ensures efficient rendering and maintainable code.
Ask candidates to render a list of products with a filter feature to show only products in stock.
Example Coding Question:
“Write a React component that renders a list of names from an array using .map().”
Create a complete test and generate more similar questions to evaluate skills of your candidates.
State management refers to how a React component stores and manages its internal data. Developers use hooks like useState to store values and useEffect to trigger actions when the component renders or updates. Good state management ensures that the user interface updates smoothly in response to actions or external data changes.
Assign a task to build a simple to-do app that stores tasks in state and updates when users add or delete items.
Example Question:
“Using useState and useEffect, create a counter that increases every second after the component mounts.”
Create a complete test and generate more similar questions to evaluate skills of your candidates.
React Router enables developers to build multi-page user interfaces within single-page applications. It allows for dynamic routing—where pages and components are rendered based on the URL. Navigation plays a crucial role in the user experience, especially in larger apps with multiple pages or features.
Provide a task to build a multi-page app with routes for login, dashboard, and error pages.
Example Question:
“Implement a route that redirects users to a 404 page if the URL does not match any available routes.”
Create a complete test and generate more similar questions to evaluate skills of your candidates.
Testing ensures that your components and functions work as expected and helps catch bugs early. Jest is a popular testing framework, and React Testing Library simplifies testing React components.
Why is it important? Testing is critical in maintaining code quality—especially when multiple developers are working on the same project.
Ask candidates to write tests for a form component to ensure it validates inputs correctly.
Example Question:
“Write a Jest test case to check if a button click triggers a state update.”
Create a complete test and generate more similar questions to evaluate skills of your candidates.
React Hooks, such as useContext and useReducer, allow developers to share state across components without passing props down manually. This improves code structure by making state available to deeply nested components.
Why is it important? Managing shared state efficiently helps reduce complexity and improve maintainability in larger apps.
Ask candidates to build a theme switcher using the Context API and hooks.
Example Question:
“Create a React context for a theme and use it to toggle between light and dark modes.”
Create a complete test and generate more similar questions to evaluate skills of your candidates.
Hiring React.js developers? A strong screening process is essential, not just helpful. A poor hire can cost you thousands of dollars and countless hours of your tech leads’ time fixing broken code. A thorough assessment helps ensure you only hire the right talent.
This guide covers the top six must-have React.js skills, providing clear explanations of why they matter and how to evaluate them with coding tasks and interview questions. With these steps, you can pre-screen candidates efficiently and hire confidently.
Please explain the best way to structure a React component for reuse in different parts of application?
Here, the candidate must inform you its best practice to break down user interface into smaller complement for reuse. They can also talk about prop-passing and conditional rendering to make sure flexibility across different use cases.
What are the guidelines for incorporating props and state in a component?
What to Listen For: When candidate is answering, carefully listen for answer that that incorporates the state used for data changes within a component, while props are used to transfer information or data in this regard from antecedented parent components to subsequent child components.
When to use lifecycle methods such as componentDidMount or componentWillUnmount?
Listen for: This is a component of class structure & a good developer will be able to recognize its uses. Look for a solution referencing componentDidMount for data retrieval or subscription establishment & componentWillUnmount for cleanup duties.
According to you, what would be the best way to handle sharing information or data among multiple component that require access to same information?
A good candidate will mention Redux or Context API, especially for larger applications. The candidate must mention why these are good solutions in compared with prop drilling.
What are the steps must be taken if a component isn’t rendering as you expected?
Your candidate here must explain the steps he or she might use briefly, look for use of tools such as - Console logs, React DevTools or maybe debugging with breakpoints.
How to handle information which comes through an external API in a React component?
Here, look for answer that cover using fetch or axios for API calls, useEffect to manage side effects & state management for storing the API response.
How to handle a form in React where users can put their data and submit it?
Your candidate here will be talking about setting up component using useState for each input field & maybe form validation
What’s the best way to make sure that the React application runs very smoothly, even with multiple components on the screen?
Candidates here possibly going to mention strategies like memoization, using React.memo for functional components & splitting components into smaller pieces.
Why do you think testing is important?
Here candidate must be enthusiast about multiple test runs to catch bugs early to make sure code reliability & to reduce issues in larger applications. The candidate might also mention Jest or React Testing Library.
How to add navigation to an app that has multiple pages?
A good React developer must be able to explain how to set up React Router with routes for all page & mention basic concepts like Link and useHistory.
What are some ways you can style a React component?
Candidates can mention here CSS modules, styled-components, inline styles, or maybe traditional CSS. This question is here to see if they’re comfortable with styling approaches.
Can you explain the advantages of using hooks such as useState & useEffect in React?
The candidate here need to explain that the hooks allow functional components to handle state & lifecycle methods, this is to make the code more smaller and reusable.
How to handle an error that occurs while loading information in a component?
A good candidate will be able to discuss error handling methods to use, for instance try/catch blocks in asynchronous functions, displaying fallback UI messages & maybe using error boundaries.
Can you give me a situation in where you will use the Context API over Redux?
A good candidate here will highlight that the Context API is better for simpler, smaller applications. They should also explain that the Redux is suitable for handling complex state management in heavy applications.
How would you block unnecessary re-rendering in a React application?
Candidates can mention use of techniques such as using React.memo, useCallback & useMemo hooks to optimize the performance by blocking or preventing unnecessary re-renders.
What steps you think is better if you have to show a large list of items in a React component?
Your candidate will give you solutions like pagination & infinite scrolling to load items slowly. They can also discuss about virtualized lists to render the only visible parts in the screen.
How would you share information or data among sibling components in a React app?
The prodpect here can mention lifting state to a common parent component or making use of a global state management solution like the Context API or Redux.
How to handle loading, success & error data when fetching in a React?
Candidates here need to describe setting up loading & error states alongside data state to manage alternative results of a fetch request. They will mention displaying a loading indicator & handling errors.
Evaluating React.js developers’ skills is not just important—it’s an absolute must. A bad hire can result in costly mistakes and wasted time. By focusing on the six essential skills—Redux, state management, loops, routing, testing, and hooks—you’ll ensure your team is built with top-notch talent.
A solid screening process, complete with real-world coding assessments and targeted interview questions, will help you pre-screen candidates at scale and hire only the best React.js developers. With the right people on board, you’ll build reliable, scalable, and maintainable applications.
Explore more examples or create your own coding assessments here:
Good luck with your screening and hiring process!
“With EliteBrains, we streamlined contracts, approvals, and payments into one simple workflow.”
