How to Prepare for React Interviews

Recommended preparation strategy

Although everyone's mastery of React is different, this preparation plan can be used by most people that have a React interview coming up.

Read react.dev: Read the "Learn" section of react.dev cover-to-cover. It's not extremely long and can be completed in a day
Read this guidebook: Read this "React Intervie Playbook" cover-to-cover. It's also not very long and can be completed in two hours
Practice: Practice makes perfect, get your hands dirty and start studying!
- Quiz questions: Practice React quiz questions on GreatFrontEnd
- Coding questions: Practice building UI questions using React on GreatFrontEnd
Read GreatFrontEnd's front end system design questions if targeting for a senior role or expecting system design rounds

Important concepts for interviews

Although by now React is a vast library by with many concepts to master and APIs to learn, not all concepts are important for interviews. This guidebook covers the most important concepts that candidates are expected to know during interviews as well as the various key points.

Basic concepts

Understanding the basic concepts in React is crucial for any front end interview, as they form the foundation of building and reasoning about React applications. This includes core concepts like components, JSX, props, state, and how rendering happens. Mastery of these basics enables engineers to construct modular, reusable UI components and efficiently manage application state. Without a solid grasp of these fundamentals, tackling more advanced topics such as hooks, performance optimizations, or state management becomes significantly more challenging.

Interviewers often test these concepts to gauge a candidate's ability to build and reason about React applications effectively. Read more about the basic concepts in React.

Thinking declaratively

React encourages a declarative programming style, where UI logic is expressed in terms of "what to render" rather than "how to render it". This approach makes code more predictable, easier to debug, and more maintainable. Instead of manually manipulating the DOM, React developers describe the UI in terms of components and state, letting React handle updates efficiently.

Understanding declarative patterns is crucial in interviews, as it reflects a candidate's ability to write clean, maintainable, and idiomatic React code. Read more about thinking declaratively in React.

State design

State design is a critical part of building scalable React applications, as poor state management can lead to unnecessary re-renders, hard-to-maintain code, and performance issues. A well-structured state design considers factors like co-locating state where it is needed, lifting state up when necessary, and minimizing unnecessary state variables. Interviewers assess candidates on their ability to decide where state should live and how to structure it for clarity and efficiency.

Mastery of state design principles is key to building robust React applications that remain performant and scalable as complexity grows. Read more about state design in React.

React hooks

React hooks, introduced in React 16.8, revolutionized state and side effect management in function components. Hooks like useState, useEffect, and useContext enable developers to handle state and lifecycle events without needing class components. More advanced hooks like useMemo and useCallback help optimize performance. Understanding hooks is crucial in front end interviews, as they are the primary way React developers manage state, side effects, and component logic in modern applications.

Candidates are often tested on their ability to use hooks correctly while avoiding common pitfalls like excessive re-renders and dependency array misconfigurations. Read more hooks in React.

Event handling

Event handling in React differs from vanilla JavaScript, as it uses synthetic events for cross-browser consistency and performance optimizations. Understanding how to work with event handlers, pass event data, and optimize event-driven logic is essential in React development. Candidates should be familiar with common patterns like preventing default behavior, handling input changes, and efficiently binding event handlers to avoid unnecessary re-renders.

Since UI interactions are central to front end applications, interviewers often test a candidate's ability to handle events in a structured and efficient manner. Read more about event handling in React.

Forms

Forms are a fundamental part of many web applications, handling user inputs and interactions. In React, managing forms involves controlled and uncontrolled components, state updates, and form validation. A strong understanding of form handling ensures a seamless user experience while maintaining performance and scalability. Interviewers frequently assess a candidate's ability to manage form state, implement validations, and handle form submissions efficiently.

Mastering forms in React is crucial for developing data-driven applications where user inputs play a central role. Read more about writing forms in React.

Data fetching

Fetching and managing data efficiently is a key aspect of React applications. Whether using fetch, Axios, or React Query, candidates need to understand how to handle asynchronous operations, caching, pagination, error handling, and performance optimizations like debouncing and memoization. Many interview questions revolve around fetching data efficiently while avoiding common pitfalls such as excessive re-renders and race conditions.

Since many React applications interact with external APIs, strong data fetching skills demonstrate an ability to build real-world applications that perform well and handle data gracefully. Read more about data fetching in React.

Design patterns

React development benefits from common design patterns that enhance code reusability, maintainability, and scalability. Patterns like higher-order components (HOCs), render props, and compound components enable developers to create flexible, modular components. More modern patterns, like hooks-based composition and context-based state management, simplify complex logic. Interviewers often test candidates on their understanding of these patterns to gauge their ability to write scalable and maintainable React code.

Strong knowledge of React design patterns showcases an ability to architect large applications in a clean, efficient manner. Read more about design patterns in React.

Performance optimization strategies

Performance optimization is a key skill in React development, as poorly optimized applications can suffer from slow renders, excessive re-renders, and sluggish user experiences. Strategies like memoization (useMemo, useCallback), virtualization (e.g., React Virtualized), lazy loading (React.lazy), and optimizing state updates help improve application performance. Front end interviews frequently assess a candidate's ability to recognize and address performance bottlenecks, ensuring smooth and efficient applications.

Demonstrating strong optimization techniques highlights a developer's ability to build high-performance React applications that scale effectively.

Concepts that you probably won't need

These concepts are either still quite new, not mature yet, or not used directly by developers, hence they aren't that relevant for interviews.

Suspense

Suspense is a React feature designed for handling asynchronous operations like data fetching, code splitting, and lazy loading components in a more declarative way.

While it's a useful tool for improving user experience, it is not commonly tested in front end interviews because there are usually higher level abstractions to use for data fetching and code splitting. Most interviewers focus on fundamental data fetching patterns (e.g., useEffect, TanStack Query, or SWR) rather than <Suspense>-based solutions.

Server components

React Server Components (RSC) are a major shift in React's architecture, allowing developers to render components on the server while reducing client-side JavaScript bundle sizes. While they offer significant performance benefits, they are still relatively new and mainly relevant for projects using frameworks like Next.js.

Since many front end interviews focus on React fundamentals and client-side rendering, RSCs are unlikely to be a priority in interviews. Most companies are still transitioning to these patterns, making them less relevant for assessing a candidate's core React skills.

Server functions

Server functions, such as those found in Next.js (API routes) or other serverless architectures, enable handling business logic on the server rather than the client.

While they are important for full-stack applications, front end interviews typically emphasize client-side concerns like component structure, state management, and UI performance. Unless interviewing for a full-stack role, knowledge of server functions is not a key evaluation criterion, as they fall outside the core responsibilities of a front end engineer focused on React.

Changes in React 19

React 19 introduces several updates, such as improvements to Suspense, server actions, new hooks, etc.

While these changes are valuable for developers staying up to date with the ecosystem, they are not typically the focus of front end interviews. Most companies prioritize a candidate's ability to work with widely adopted React patterns rather than the latest experimental features. Since React 19 is still being adopted, interviewers are unlikely to expect deep knowledge of its updates unless specifically mentioned in a job description.

React compiler

React Compiler is an upcoming optimization tool that aims to improve performance by automatically optimizing React code at build time.

While it promises efficiency gains, it has not yet been widely adopted and remains in an early phase. Since front end interviews typically focus on hands-on problem-solving and existing optimization techniques (useMemo, useCallback, etc.), the React Compiler is not a crucial topic for candidates to study.

Until it becomes a standard part of the React ecosystem, it is unlikely to appear in most front end interviews.