Frontend mock interviews
A frontend round rarely stops at "what is a closure". It moves from a small answer to how the browser actually behaves under it, and most candidates lose ground on the second or third follow-up rather than the first question.
Rounds with Sia from ₹49 · Live interviews with a working engineer from ₹500 · Pay per session
What a Frontend round covers
Rendering and the DOM
How the browser turns markup into pixels, what forces a reflow, and why a change that looks cheap in code is expensive on screen. Expect to be asked what happens between a state update and a repaint.
State and data flow
Where state should live, what makes a component re-render, and how you would explain a stale-closure bug to someone who has just hit one. Framework-specific follow-ups depend on the stack you pick.
The event loop and async
Microtasks against macrotasks, why a promise resolves before a timeout, and how you would debug an interaction that feels janky without reaching for a profiler first.
Accessibility and semantics
The part most candidates skip. Choosing the right element, keyboard behaviour, and what a screen reader announces — asked as a design decision, not as trivia.
Frontend interview questions you might be asked
Not a list to memorise. Each is the kind of opening a real round uses, with what a strong answer covers — the follow-ups depend on what you say.
A list of 2,000 rows scrolls badly on a mid-range phone. Walk me through how you would find out why.
Measure before fixing: what re-renders on scroll, whether layout is being forced, and only then reach for virtualisation or memoisation, saying what each one costs.
A click handler reads a state value and gets the old one. What is going on?
A stale closure: the handler captured the value from an earlier render. A strong answer explains why, then gives two fixes and when each is the right one.
Build a dropdown menu. What does it need beyond opening and closing?
Keyboard support, focus handling, what a screen reader announces and closing on outside click — raised by you, before the interviewer has to ask.
Why does this promise callback run before the setTimeout written above it?
Microtasks against macrotasks, explained as a queue the event loop drains, plus one real bug this ordering has caused.
Where would you keep the logged-in user, and where would you keep a form that is half filled in?
Different answers for different lifetimes: shared app state against local state, and why putting everything in a global store has a cost.
Answer questions like these in a scored round and see exactly where your answer fell short.
What the interviewer is listening for
Interviewers are listening for whether you can move between levels: the API you use, the mechanism underneath it, and the trade-off you accepted. Naming the trade-off out loud scores better than an answer that quietly assumes it.
Where candidates lose marks
- Reciting a framework API without being able to say what it does underneath.
- Going quiet while thinking, so the interviewer cannot tell whether you are stuck or working.
- Treating accessibility as an afterthought when asked to build a component.
Two ways to interview
A round with Sia, on your own
One question at a time with real follow-ups on what you actually said. Choose three, five or eight questions. Scored the moment you finish, with a written breakdown across technical depth, problem solving and communication.
A live interview with an engineer
Forty minutes over Zoom with someone who runs frontend interviews for a living. They score five criteria and write up what to fix, and you keep a numbered certificate for the session.
Pick your stack for a round with Sia: React · Angular · JavaScript · HTML · CSS · React Native.
Questions about frontend interviews
Do I need to know React to take a frontend round?
No. Pick the stack you are actually interviewing in — React, Angular or plain JavaScript, HTML and CSS — and the follow-ups follow that choice. The fundamentals underneath (rendering, the event loop, accessibility) are asked either way.
Is a frontend round right for a fresher?
Yes. A round with Sia can be set to Beginner, Standard or Senior difficulty, so a first-job candidate is pushed on fundamentals rather than on architecture they have not had the chance to build.
Will I write code in the round?
Expect to talk through code more than type it: what a snippet does, why it misbehaves and how you would change it. Explaining your reasoning out loud is part of what is scored.
How is a frontend round scored?
On the same five criteria as every round — technical depth, problem solving, communication, behavioural and code quality — with a written breakdown of what to fix.
Read before your round
Frontend interviews by technology
Other tracks
Not sure which to book? The FAQ covers how sessions are scored, and candidate stories show what people did with the feedback.