Skill Test · React · Coming soon
React Online Test for Hiring & Assessment Coming soon
Coming soon: the React test pack is not yet available. What follows describes the intended scope. A React online test measures a candidate's understanding of the functional component model, hooks semantics, data flow patterns, and performance trade-offs. It goes beyond "have you used React before?" to test whether a developer can reason about why React re-renders, when memoisation helps, and how to avoid common hook mistakes that only show up at scale.
Topic breakdown
What the React test covers
Hooks deep dive
useState, useEffect (cleanup, dependency array), useRef, useContext, useReducer. When to use each, and what mistakes cause stale closures or infinite re-renders.
Component lifecycle
Functional component render cycle, when effects fire relative to paint, how React batches state updates (React 17 vs React 18 automatic batching), and Strict Mode double-invocation.
State and data flow
Unidirectional data flow, prop drilling and when it becomes a problem, lifting state up, Context as a solution vs Redux or Zustand, and controlled vs uncontrolled inputs.
Performance optimisation
React.memo for component memoisation, useMemo and useCallback (correct use cases and common misuse), key prop correctness in lists, and how to use the React DevTools Profiler to find re-render hot-spots.
Patterns and composition
Compound components, render props, custom hooks for logic reuse, the children pattern, and conditional rendering strategies that avoid unnecessary DOM thrashing.
Error boundaries and suspense
Class-based error boundaries, where they catch and where they don't, React.lazy for code splitting, Suspense for async loading states, and the ErrorBoundary + Suspense composition pattern.
Illustrative example (not from a live test)
The kind of question candidates answer
useEffect dependency array — mid level
What is the problem with this component, and how would you fix it?
function UserProfile({ userId }) {
const [user, setUser] = useState(null);
useEffect(() => {
fetch(`/api/users/${userId}`)
.then(r => r.json())
.then(data => setUser(data));
}, []); // empty dependency array
return user ? <div>{user.name}</div> : <p>Loading...</p>;
}Correct answer and approach
The effect runs once on mount and never re-runs, so if the parent passes a different userId later, the component still shows the original user. Fix: add userId to the dependency array: [userId]. Additionally, the effect should return a cleanup function that aborts the fetch (via AbortController) to prevent state updates on unmounted components.
What this question tests
Understanding that an empty dependency array means "run once on mount, never again" — not "run whenever I feel the data might be stale." The AbortController follow-up separates mid-level from senior candidates. Both mistakes cause real production bugs (stale data and memory leaks on route changes).
Who should take it
Roles this test screens for
Frontend / React Developer
The primary use case. Pair with the JavaScript core test for a complete frontend screening session.
Full-Stack Engineer
Screens the frontend half of a full-stack role. Combine with an SQL test or Python test for the backend side.
Tech Lead / Senior Engineer
Performance and architectural pattern questions at senior tier probe whether a candidate can design a component system, not just build a single component.
Relevant for IT & technical hiring across product and startup engineering teams in India.
Format & difficulty
Duration, format, and difficulty levels
Duration
Coming soon
Confirmed at launch
Format
Coming soon
Confirmed at launch
Levels
Coming soon
Confirmed at launch
FAQ
Common questions about the React online test
Is the React test available on AssessIQ?
Not yet. The React test pack is coming soon. Contact us and we will tell you when it launches.
Which AssessIQ test is available today?
The Aptitude test pack (multiple-choice, scored automatically) is live. Written, scenario and log-analysis questions can be graded with AI assistance by AssessIQ evaluators.
- JavaScript Online Test
Pair with React for a complete frontend screening session.
- Python Online Test
Add backend language screening for full-stack roles.
- SQL Online Test
Database query proficiency for full-stack and API roles.
- All skill tests →