Prepare for your next React interview, using our 100 tricky code questions, it is short simple and have code as well
100 senior-level React questions covering hooks, performance, state management, and common pitfalls
Why is useEffect(async () => {}) not recommended?
What is a stale closure?
Why shouldn't you use array index as a key?
When does useMemo NOT help?
useCallback vs inline function trap
Why does this cause infinite re-renders?
What happens if you mutate state directly?
Why doesn't this re-render?
Difference between useEffect and useLayoutEffect?
Controlled vs uncontrolled input trap
Why does this child re-render?
What is React reconciliation?
Why is lifting state sometimes bad?
Why does Context cause performance issues?
Why does React.memo not work here?
Difference: state vs ref
Why batching matters
What is flushSync?
What is StrictMode double rendering?
What is a memory leak in React?
Why is derived state an anti-pattern?
What is render props?
Why Suspense can break data fetching?
What is virtualization?
Why this breaks memoization?
Why is setState async?
Why shouldn't you fetch in render?
What is prop drilling vs composition?
Why fragments help?
What is the biggest React interview trap?
Why does this component re-render even with React.memo?
Why does useEffect run twice in React 18?
Difference between useEffect cleanup & unmount?
Why is this fetch duplicated?
Why does this state update behave unexpectedly?
Why does this cause a race condition?
What is tearing in React?
Why is useState initializer a function?
Difference: useRef vs closure variable?
Why does this infinite loop happen?
Why is useCallback sometimes useless?
Why does this break SSR?
What is hydration mismatch?
Why is Context not a state manager?
Why does this break useEffect deps rule?
Why does this event handler see old state?
What is useTransition used for?
Why is useDeferredValue useful?
Why does this break memoization?
What is the difference between render & commit phase?
Why is children sometimes better than props?
Why does this list scroll jump?
Why does this break controlled input?
What is render-as-you-fetch?
Why does this leak memory?
Why shouldn't you store JSX in state?
What is the "state colocation" principle?
Why is forwardRef needed?
Why does this break accessibility?
Ultimate React interview killer question
Why does this component remount instead of re-render?
Why is this useEffect dependency wrong?
Why does this cause unnecessary re-renders?
Why does setState inside render crash?
Why does this break memoization?
What happens if you call hooks conditionally?
Why does this effect never run?
Why does this ref callback fire twice?
Why is useImperativeHandle used?
Why is this input laggy?
Why does this break batching?
Why does useEffect see outdated props?
Why is this state update ignored?
Why does this list flicker?
What is the difference between memo and PureComponent?
Why does this cause hydration warning?
Why does this effect run on every render?
Why shouldn't you store derived data?
Why does this break React DevTools?
Why does this event handler cause stale state?
Why does this crash in production only?
Why is useEffect not guaranteed to run?
Why does this break Suspense?
Why is this component slow?
Why is this an anti-pattern?
Why does this cause layout shift?
Why is dangerouslySetInnerHTML dangerous?
Why does this break reconciliation?
Why does this state reset?
Why is this event pooled?
Why does setState inside effect cause loop?
Why does this break accessibility?
Why is this bad for performance?
Why does this crash silently?
Why should error boundaries be class components?
Why is this render blocking?
Why is useId needed?
Why does this break memo?
Why is defaultProps deprecated for functions?
Final React interview killer question
Everything you need to succeed in your React interview
Curated collection of the most challenging React interview questions that actually get asked.
In-depth answers with code examples, best practices, and common pitfalls to avoid.
Real-world code snippets and interactive examples to solidify your understanding.
Comprehensive coverage of all React concepts
useState, useEffect, useContext, custom hooks
Memoization, lazy loading, optimization
Redux, Context API, Zustand
HOCs, render props, compound components
Jest, React Testing Library, E2E tests
Types, interfaces, generics with React
SSR, SSG, API routes, App Router
Code organization, accessibility, security
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