React Interviews: An Introduction

React has firmly established itself as the de facto standard for modern front end development. It powers everything from small web applications to massive enterprise platforms used by millions of people. Whether you're building interactive dashboards, e-commerce websites, or social media platforms, chances are you're using React or something inspired by it.

Many companies use React to build user interfaces and their technical interview process will assess a candidate's React knowledge and skills. This guide is for anyone preparing for technical interviews where React skills are relevant and focuses on the important concepts and knowledge for interviews. It is not meant to teach you React, or replace the excellent React documentation website.

The content is pretty light and you should be able to complete reading cover to cover within an afternoon.

However, if time permits and especially if you haven't visited the official React documentation website in a while, we recommend you read through the entire "Learn React" section while skimming through the examples within each page as well as the latest blog posts. React is evolving at a pretty fast pace and it's good for you to read the official docs every now and then to catch up on the latest updates. It should not take longer than two afternoons.

Who this guide is for

Whether you're applying for a front end engineering position, a full-stack role, or a React-specific job, if you're in one of the following categories, this guide will be useful to you:

• Front end engineers: If you're aiming for roles that heavily focus on React, JavaScript, and UI development, this guide will give you a structured way to prepare.
• Full stack developers: If React is just one part of your job, but you still need to prove your expertise in building UI components and managing front end state, this guide, along with our practice questions will hone your React skills.
• Experienced engineers looking for a refresher: If you already use React heavily at work but want to prepare specifically for React interviews, this guide will fill in the gaps.

Whether you're targeting an entry-level job or a senior position, the React Interview guide will help you systematically prepare for technical interviews by covering everything from fundamentals to advanced concepts.

This guide is not for:

• Complete beginners to React: This guide assumes familiarity and prior hands on experience with using React for building user interfaces; start with the official React docs
• Developers looking to dive into React internals: Focuses on practical interview prep, not React's internal source code; check out JSer's React Internals Deep Dive series, Rodrigo Pombo's Build your own React, Tiger Abrodi's GitHub projects, and Build your own X
• Those preparing for general software engineering interviews: This guide does not cover data structures, general system design, or algorithms in depth; try Tech Interview Handbook and NeetCode
• React Native developers: While a lot of relevant React concepts will be covered, the guide does not touch on mobile-specific topics
• People just looking for a list of questions and answers: The guide explains concepts and teaches you the patterns relevant in React interviews, not just provide answers for you to memorize; For a list of React interview questions, check out GreatFrontEnd's React interview questions

If you already know React and want to excel in interviews, this guide is for you! 🚀

Types of companies and their interview processes

Big tech companies like Meta and Google focus on fundamentals and all coding has to be done using Vanilla JavaScript; React is hardly relevant. It's crucial for you to find out from the recruiters what sort of questions to expect so that you optimize your preparation!

Here's a breakdown of React's relevance, key topics, and example questions for each type of React interview question.

Types of React interview questions

React knowledge can be tested in (but are not limited to) the following question formats.

Quiz / trivia

Quiz-style questions test fundamental React knowledge, helping interviewers quickly assess a candidate's familiarity with React's concepts, APIs, and best practices.

While it is possible to clear this type of questions purely by memorizing the answers, we wouldn't recommend as the concepts can also be tested in the other question types and it is more important to understand and apply the relevant concepts when the situation arises.

Important topics

• Fundamentals: JSX, components, rendering (virtual DOM, reconciliation)
• Component design: Thinking declaratively, props, state, structure
• React hooks: Common hooks (e.g. useState, useEffect), rules of hooks, best practices
• Differences between controlled and uncontrolled components
• Event handling in React
• Common pitfalls (e.g., stale closures, unnecessary re-renders)
• Performance optimizations: memoization, lazy loading, React Profiler

Example questions

• What is the difference between controlled and uncontrolled components?
• How does React's reconciliation algorithm work?
• Explain the difference between useEffect and useLayoutEffect
• What happens when the state is updated in React?
• How does React.memo help with performance?
• Why should you use a key prop when rendering a list?

Check out the full list of React quiz questions.

User interface coding questions

These questions assess a candidate's ability to implement UI components with React, focusing on creating interactive and visually accurate components.

Important topics

• Prop design and component composition
• State design and state management
• Event handling
• Styling approaches (CSS Modules, Styled Components, Tailwind)
• Conditional rendering and rendering list of items
• Accessibility (a11y best practices)

Example questions

• Implement a tabs component
• Implement an autocomplete component
• Implement a basic sign up form
• Build a reusable modal component with an overlay and close functionality
• Build a memory game

Check out the full list of React user interface coding questions.

Implement React hooks

Hooks are a core part of modern React development. These questions test a candidate's understanding of hooks, their use cases, and their ability to manage state and side effects.

Important topics

• useState, useEffect, useMemo, useCallback, useRef
• Custom hooks and reusability
• Handling side effects properly
• Dependency arrays and stale closures
• Performance optimizations with hooks
• Handling async operations in hooks (e.g., useEffect with fetch)

Example questions

• Implement useWindow, a custom hook that tracks the window size and returns width and height
• Implement useDebounce, a hook that delays the execution of a function
• Implement usePrevious, a hook to track the previous state value
• Implement useLocalStorage, a hook that reads and writes values to localStorage

Take-home assignments

Take-home assignments evaluate a candidate's ability to build a real-world React application within a given timeframe, with a focus on code quality, maintainability, and best practices.

Most take-home assignments involve fetching data from an endpoint and filtering + sorting of that data.

Important topics

• Component architecture and reusability
• State management (Context API, Redux, Zustand)
• API fetching and error handling
• Performance optimizations
• UI/UX considerations
• Code structuring and readability

Example take-home assignments

• Build a simple task management app where users can add, edit, and delete tasks
• Implement a e-commerce product listings page that allows for searching, filtering, and sorting
• Create a weather app that fetches data from an API and displays weather conditions dynamically
• Design and implement a dashboard with charts using React and a charting library

System design

System design questions test a candidate's ability to architect scalable, maintainable, and performant front end applications.

System design questions can broadly be classified into two types:

• Application design: App design questions aren't specific to any front end technology but sometimes interviewers might ask you how you would implement a specific section and you would have to mention concrete libraries/approaches using React/Vue/Angular/Svelte/etc and which of their APIs you'd use.
• Component design: Component design questions are about implementing a reusable, extensible, and accessible component for a specific purpose using a specific JavaScript framework of your choice or Vanilla JavaScript if you're adventurous enough. Hence mastery of the JavaScript framework is essential and component design in order to design the right props and composition mechanisms.

Important topics

• Component hierarchy and modularization
• State management strategies (global vs local state)
• Server-side rendering (SSR) vs client-side rendering (CSR)
• Performance optimizations (lazy loading, memoization, list virtualization)
• Data fetching mechanisms and how to implement them (e.g. caching, debouncing, retries, optimistic mutations)
• Error handling and fallback UI strategies

Example questions

• How would you implement infinite scrolling within a news feed?
• How would you design the component hierarchy within a music player?
• How would you implement a modal dialog component in React?
• How would you implement a dropdown menu component in React?

Check out the full list of front end system design questions.

Scope of the guide

Preparing for a React interview can feel overwhelming. There's a lot to cover, and not all topics are as important for interviews. This guide cuts through the noise and focuses on the topics that matter the most.

This guide is structured to help you master React interviews in a systematic way. Each section builds on the previous one to help you understand not just what React does, but why it works the way it does, and what you absolutely need to know for interviews.

We do not recommend memorizing answers; it's better to gain a good understanding of React so you can confidently tackle any question or variants that comes your way. You'll probably even learn new things along the way that will make you more skillful in using React!