Soft questions: How do you deal with conflicts? What role(s) do you take in a team? Strengths/weaknesses (in some form) Tell me about a stressful situation you experienced, what did you learn from it? React questions (junior to senior): Describe how to use useState. What happens with a component when it receives new props? How can you share a state between multiple components? Do you have to use React with JSX? What is the difference between a controlled and uncontrolled component/input/element/form? What is the VDOM (Virtual DOM)? What are some common pitfalls when doing data fetching? Describe the usage and pitfalls of useEffect (open discussion). JS Questions (junior to senior): What is the difference between let and const? What is a callback, when would you use one? What is the difference between == and ===? What is hoisting? What is a closure? What is the event loop? When is it a good idea to use a class (open discussion). These are some from the top of my head, questions I have been asked or asked candidates during interviews. More on reddit.com

Here is my own checklist I'm using when interviewing candidates, perhaps will be helpful for you to structure the subject. Then I suggest you to make a written notes. After all you might not know something, but the core stuff and ability to think is a must. General When do components re-render? When props change, state changes, or the parent re-renders. How are key attributes used in reconciliation? Elements of the same type with the same key attributes in an element subtree are assumed to be unchanged. What is StrictMode? Works only in development, shows deprecated APIs, runs effects twice. How does React.SyntheticEvent differ from a browser event? React SyntheticEvent provides a consistent interface for handling events across different browsers, improves performance through event pooling and event delegation, and simplifies event handling with automatic binding. What is event delegation? Follow-up question related to React SyntheticEvent. Context What are the differences between Context and Redux? How to consume multiple contexts? Context vs Redux Pros: Lighter bundle, easier setup, can be migrated to Redux. Cons: Less features out of the box, no selector API, performance, and security issues (context ref is passed to every dependent object). JSX What is JSX fundamentally? React.createElement(component, props, children). Is it closer to JavaScript or HTML? Can one write React without JSX? Components How to declare a React component? Why does one need to use a capital first letter when naming a component? All React components must act like pure functions with respect to their props. Code-splitting How to dynamically import modules? What are the limitations of Suspense and React.Lazy? No SSR, only default exports. Performance Optimization Long lists virtualization Avoid reconciliation Two components of different types produce different trees, key attributes are used to preserve unmodified components. Pure components, React.memo Memoization Portals What is it? Used for? Does it support event bubbling? Profiling What is Profiler? What happens in prod build? Refs When do we need refs? How to pass a ref through a component to one of its children? Using forwardRef. Render Props What is it? Technique to share code between components using a prop whose value is a function. Use cases renderHeader, renderItem, renderRow. Strict Mode What is it used for? Unsafe lifecycles, deprecated APIs, unexpected side effects. What happens in prod build? Uncontrolled Components What is it? Form data handled by the DOM, not by React. How to specify the initial value to uncontrolled input? defaultValue attribute. Web Components How to use WC in React? How to use React in WC? Hooks How to emulate lifecycle methods in FC? How to store complex state with hook? When to use useCallback? When to use useLayoutEffect? Custom hooks: Do two components using the same hook share the state? New React Features Concurrency Transition API Batched updates More on reddit.com

Congratulations on landing the interview! You can check out these websites for some prep questions: BFE.dev GreatFrontEnd Front End Interview Handbook Front-end Developer Interview Questions Good luck with everything! More on reddit.com

Why does infinite re-rendering happen in a useEffect and how do you prevent it Describe a scenario in which you would use useMemo Why is Typescript/TSX used for large applications Provide a large but working component (300-500 lines or so) and ask them to refactor it into reusable components and utility functions More on reddit.com