After interviewing many React developers, I’ve realized that interviews aren’t about catching people off-guard or seeing what they don’t know. What I really want is to understand how someone thinks, how they approach problems, and how they’ve grown through their experiences.
These are the areas I naturally pay attention to, not because I expect perfection, but because they give me a clearer picture of someone’s comfort level with real-world frontend development.
1. JavaScript Fundamentals: The First Filter
Before I ask anything about React, I look for solid JavaScript fundamentals.
Not trivia. Not trick questions.
But questions that reveal understanding of:
- closures
- async/await & the event loop
- immutability
- objects vs references
- array/object manipulation
Weak JavaScript always shows up later as weak React.
Strong JS tells me the candidate can reason about UI behavior without stumbling into guesswork.
2. HTML & CSS Mastery: The Underestimated Skill
A surprising number of candidates can’t structure accessible HTML or reason about CSS specificity.
So I pay attention to:
- semantic markup
- flex/Grid awareness
- responsive thinking
- accessibility basics
Because at the end of the day, React renders HTML and CSS—not magic.
Their approach here reveals whether they can build interfaces that are clean, accessible, and production-ready.
3. React Fundamentals: Depth Over Definitions
When I ask about reconciliation, controlled inputs, keys, or component composition, I’m not testing memory.
I’m testing understanding.
I want to see if candidates genuinely know why React behaves the way it does—not just that “it re-renders sometimes.”
Clear reasoning here shows me they can prevent issues before they appear.
4. Hooks: The Real Difference-Maker
Hooks expose a developer’s thought process instantly.
So I probe their understanding of:
- dependency arrays
- stale closures
- memoization logic
- custom hooks for reusability
The best candidates don’t just know how to use hooks—they know why hooks behave the way they do.
Good hook explanations show they understand state, side effects, and component lifecycles on a deeper level.
5. State Management: Architectural Thinking
This is where seniority becomes obvious.
Strong candidates can explain:
- when to use Context vs Redux vs Zustand
- the difference between server state and client state
- caching strategies
- selectors and memoization
Average candidates choose tools.
Senior candidates justify them.
Their choices here reveal their architectural maturity and thoughtfulness.
6. Deep Understanding of Their Own Project
This is the biggest differentiator.
I don’t want a tour of their GitHub.
I want to see:
- how data flows in their app
- what patterns they use
- how they handle performance challenges
- how they break down large features
- why they made architectural decisions
If someone can’t explain their own application clearly, I can immediately tell they weren’t involved deeply.
The depth of their explanation tells me how involved they really were and how well they understand complex systems.
7. Performance Optimization: The Senior Signal
I often ask questions like:
- “Why does this component re-render?”
- “How would you optimize this list?”
- “Where would memoization help—or hurt?”
Great engineers don’t jump to useMemo blindly.
They talk about causes, not just fixes.
Their approach here shows whether they can keep an app fast, even at scale.
8. Architecture & Design Thinking
I always look at how candidates:
- structure folders
- break down components
- avoid props drilling
- design for reusability
- handle side effects
React is just a UI layer—architecture is the real skill.
This part reveals how they operate inside large, evolving codebases.
9. TypeScript: The Modern Essential
Most interviews now include TypeScript.
I check whether candidates can:
- type props
- type hooks
- use utility types
- handle API responses safely
I’m not looking for TS gurus.
I’m looking for engineers who understand how TS reduces runtime bugs.
Good TS habits tell me they write safer, more predictable UI code.
10. Async Logic & Real-World Scenarios
This is where many candidates stumble.
I want to hear how they handle:
- loading & error states
- retries and fallback UI
- parallel requests
- data caching (TanStack Query is a big plus)
- Suspense in modern React
How they think about async workflows tells me whether they can build resilient user experiences.
11. Testing: The Sign of a Mature Engineer
I listen for:
- understanding of React Testing Library
- mocking strategies
- testing asynchronous behavior
- testing components using context/hooks
Tests say a lot about the engineer writing them.
Their testing mindset shows how much they value long-term stability.
12. Awareness of React 19+
Even if they haven’t used it, awareness of:
- server components
- actions
- Suspense improvements
- transitions
…shows they’re staying relevant.
Staying updated tells me they’re committed to evolving with the ecosystem—not stuck in old patterns.
Final Thoughts: What Truly Stands Out
When you interview someone, you do not expect them to know everything.
I certainly don’t know everything myself.
What I appreciate most is:
- clarity
- reasoning
- technical humility
- strong fundamentals
- an ability to explain their decisions
- and real ownership of the projects they’ve built
Those are the candidates who instantly stand out.
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