Start with JavaScript depth — closures, the event loop, promises, prototypes — then go deep on one framework, ideally React or Next.js, including hooks, state management with Redux, and rendering behaviour. Build two projects you can explain line by line, practise machine-coding problems like debounce or infinite scroll, and finish with frontend system design basics plus mock interviews. Most working professionals in India need six to ten weeks of consistent, focused preparation.

If you already work with React daily, four to six weeks of focused revision is usually enough; if you're switching from service-based projects or returning after a career gap, plan for two to three months to cover JavaScript depth, framework internals, and system design. Consistency beats intensity — ninety minutes daily with a weekly mock interview moves you faster than weekend cramming.

Expect HTML/CSS layout questions (flexbox, grid, specificity), core JavaScript (closures, hoisting, event loop, debouncing), React fundamentals (virtual DOM, hooks, keys, props vs state), plus browser performance and accessibility. For roles with three or more years of experience, add component architecture and frontend system design, and be ready for live machine-coding rounds — building an autocomplete, todo app, or API-driven widget is standard across Indian product companies.

Shift from theory to judgment: be ready to explain what causes re-renders, when useMemo and useCallback actually help, controlled versus uncontrolled components, and how you would debug a slow page. Rebuild small features without libraries, question every abstraction in your own project code, and practise answering "why" follow-ups aloud — that is where candidates who know the basics still fail.

Fresher rounds usually cover components vs elements, props vs state, useState and useEffect, keys in lists, conditional rendering, and simple live tasks like a counter, todo app, or API call with loading and error states. Pure JavaScript carries heavy weight at this level — array methods, promises, var/let/const — and interviewers expect you to walk through one project end to end, not just show a certificate.

At four-plus years, questions move to architecture and trade-offs: structuring a large Next.js application, server vs client components, Redux vs context vs server state, performance profiling, code splitting, testing strategy, and frontend system design such as "design a news feed." Strong answers sound like production experience — a problem you hit, options you weighed, and the result — so prepare real stories from your own codebase instead of textbook definitions.

Memorized answers clear the first five minutes, not the round. The moment an interviewer extends the question — "what happens if the dependency array changes?" — a rote answer collapses, and that collapse is exactly what they screen for. Use question lists to find your gaps, but prepare by writing and explaining real code so your answers sound like experience rather than recall.

Self-study works if you are disciplined and already landing interview calls. A course pays off when you need structure, accountability, and correction on code you cannot objectively judge yourself. Recorded content is cheap, but feedback is scarce — that is why many developers in India now prefer live classes or 1:1 mentorship, where a senior reviews your actual code and runs mock rounds, instead of buying another set of videos.

A useful guide covers JavaScript core, React and Next.js depth, CSS and layout, browser and performance fundamentals, machine-coding problems with worked solutions, frontend system design, and a week-by-week revision plan. If it only lists questions without teaching you how to articulate answers, it is a question bank, not a guide — and the depth should match your experience level, since fresher material will not prepare you for design rounds.

Judge platforms on feedback quality, not content volume, because content is already free everywhere. The things that actually move results are human mock interviews with detailed debriefs, code review on your real projects, quick doubt-clearing access to a mentor, and matching for your experience level — fresher, career switch, or five-plus years. A platform offering only recorded videos and quizzes is reference material; preparation begins when someone critiques your work.

GitHub repositories are excellent for breadth — question banks, cheatsheets, and machine-coding problem sets — but reading answers creates a false sense of readiness. Interviews test whether you can produce and explain code under pressure, so convert every repo list into a loop: attempt first, check the solution, then say your answer out loud. Repos also rarely cover system design depth or personal blind spots, which is where most experienced candidates actually get rejected.

Reddit is genuinely valuable for real interview experiences, company-specific round breakdowns, and honest salary context that official preparation content never mentions. The catch is that advice is anecdotal, heavily US-flavoured, and skewed toward lucky outcomes — one developer's "I crammed for a week" is not a preparation plan. Use threads for research and signal, then build your own structured plan and pressure-test it with a mock interview.

Free resources — official documentation, YouTube, and open-source question banks — are enough to build strong fundamentals, and many developers do clear interviews on free preparation alone. What free material cannot do is spot your specific weaknesses: a bad coding habit, vague system design answers, or an ATS-unfriendly resume. A practical middle path is free self-study plus a few paid mock interviews or a resume review before you start applying to product companies.