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Frontend Development Interview Questions in Hyderabad

36 practice questions with answers for Frontend Development interviews in Hyderabad.

Frontend Development jobs in Hyderabad

Hyderabad has large engineering and capability centres of global technology, banking and pharma companies around HITEC City and the Financial District. Many roles are with global capability centres that work with teams in the US and Europe.

Below are 36 questions that match the mix of service, product and domain employers hiring frontend developers in Hyderabad.

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Tailwind classes built dynamically like 'bg-' + colour work locally but are missing in production. Why?

CSS Architecture and AccessibilityMedium

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Tailwind finds classes by scanning source files for complete strings, so a class assembled at runtime never appears in the code and its CSS is not generated. The fix is to map values to full class names, such as const colours = { success: 'bg-green-600', error: 'bg-red-600' }. If truly dynamic values are needed, use inline styles with CSS variables or explicitly safelist those classes.

Most of your users are on low-end Android phones with slow networks. How does that change your approach?

Web PerformanceMedium

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I would test with real budget devices and network throttling rather than a fast laptop. The priorities become sending less JavaScript, rendering important content on the server, compressing images aggressively, and keeping the initial page under a strict size budget. Caching with a service worker helps repeat visits. Features like large animations and heavy carousels should be reduced or loaded only when the device can handle them.

Should you use enums or string literal unions?

TypeScriptMedium

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TypeScript enums generate runtime JavaScript objects, and numeric enums accept any number, which weakens safety. String literal unions like type Status = 'draft' | 'published' have zero runtime cost, work naturally with JSON and give the same autocomplete. When you need a runtime list of values, an as const object plus a derived type works well. Many teams avoid enums, especially since type-stripping tools do not support them.

An audit finds twenty performance issues. How do you decide what to fix first?

Web PerformanceMedium

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Situation: a Lighthouse and field data audit of our app listed many issues. Task: I had one sprint to show improvement. Action: I ranked issues by user impact and effort, focusing first on the LCP image, render-blocking CSS and one oversized library on the most visited pages. Result: these three fixes delivered most of the gain, and I scheduled the remaining smaller items into later sprints.

What is the difference between a Web Worker and a Service Worker?

Browser APIsMedium

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A Web Worker runs JavaScript on a background thread for a single page, used for heavy computations like parsing files or image processing without freezing the UI. A Service Worker sits between the page and the network for an entire origin, intercepting requests to enable offline support, caching and push notifications. It has a lifecycle of install, activate and fetch, and it works only over HTTPS.

How do you estimate the time needed for a frontend feature?

Frontend ArchitectureMedium

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I break the feature into small parts: components, states such as loading, empty and error, API integration, responsive behaviour, accessibility and tests. I estimate each part, add time for reviews and unknowns, and flag dependencies like pending designs or APIs. For example, a filter panel I estimated at five days was delivered in five because I had listed edge cases upfront instead of discovering them late.

What is prefers-reduced-motion and why should you respect it?

CSS Architecture and AccessibilityEasy

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prefers-reduced-motion is a media query that detects when users have asked their operating system to minimise animation, often because motion causes dizziness or nausea. Inside @media (prefers-reduced-motion: reduce), you should remove or tone down parallax, large transitions and auto-playing animations, while keeping essential feedback such as simple fades. It is a small change that makes interfaces accessible to people with vestibular disorders.

Errors from failed promises are silently disappearing in production. How do you catch them?

Modern JavaScriptMedium

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Promises without a catch produce unhandled rejections that do not stop the app but hide failures. I would add a global window.addEventListener('unhandledrejection') handler and window.onerror that report errors to a monitoring tool like Sentry with source maps. In code, every async call should have try and catch or a .catch, and ESLint rules such as no-floating-promises in TypeScript projects catch missing handlers.

What is tree shaking and what can prevent it?

Build Tools and ToolingMedium

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Tree shaking removes exports that are never imported from the final bundle. It relies on static ES module imports and exports. It fails with CommonJS modules, dynamic property access on imported objects, and code with side effects that the bundler must keep. Libraries mark themselves safe with sideEffects: false in package.json. Importing { debounce } from a modular package instead of the whole library lets tree shaking work.

The bundle analyser shows two copies of the same library. How do you fix it?

Build Tools and ToolingHard

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Duplicates happen when different packages depend on incompatible versions, so the package manager installs both. I would run npm ls library-name or pnpm why to see who requires which version, then update dependents to a common version, use overrides or resolutions to force one compatible version, or configure resolve.dedupe in Vite. Duplicate framework copies are especially harmful because they can break shared state and context.

Write a minimal observable store in plain JavaScript.

Frontend ArchitectureMedium

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A store holds state and notifies subscribers: function createStore(initial) { let state = initial; const listeners = new Set(); return { get: () => state, set(update) { state = { ...state, ...update }; listeners.forEach(fn => fn(state)); }, subscribe(fn) { listeners.add(fn); return () => listeners.delete(fn); } }; } const cart = createStore({ items: 0 }); const stop = cart.subscribe(s => (badge.textContent = s.items)); cart.set({ items: 2 }); The returned unsubscribe function prevents memory leaks.

What is the difference between unit, integration and end-to-end tests?

Frontend TestingEasy

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A unit test checks a single function or module in isolation, such as a price formatter. An integration test checks several pieces working together, like a form component with validation and an API call mocked at the network level. An end-to-end test drives a real browser through a complete user flow, such as signup to dashboard, against a running app. They trade speed for realism in that order.

Your app must now support an Arabic right-to-left version. What changes are needed in CSS?

CSS Architecture and AccessibilityMedium

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I would set dir='rtl' on the html element for that locale and replace physical properties like margin-left, padding-right and left with logical ones such as margin-inline-start and inset-inline-start. Flexbox and Grid follow direction automatically. Directional icons like arrows need flipping with a transform in RTL, while logos and media do not. I would test layouts with real Arabic text, which has different line heights.

How do you handle a designer who expects pixel-perfect matching on every device?

CSS Architecture and AccessibilityMedium

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Situation: a designer flagged small spacing differences between Figma and my build on several phones. Task: I needed to address concerns while keeping the layout fluid. Action: I fixed genuine mistakes immediately, then showed how fixed pixel values would break on other screens and proposed shared spacing tokens. Result: we agreed on tokens and breakpoints, and future handoffs had far fewer revision rounds.

Why does await inside forEach not wait for each item?

Modern JavaScriptMedium

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forEach ignores the promise returned by an async callback, so all callbacks start almost at once and forEach finishes before any await completes. Code after it runs too early. For sequential processing, use a for...of loop with await inside. For parallel processing with a final result, use await Promise.all(items.map(async item => ...)). Choosing between them depends on whether order and rate limits matter.

State is passed through many component layers and global state has become chaotic. How do you restructure it?

Frontend ArchitectureMedium

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I would first classify state: server data moves to a data-fetching cache like TanStack Query, URL-worthy state such as filters moves to query parameters, and truly local state moves back into components. What remains global, like user session and theme, goes into a small, well-defined store or context split by concern. Composition patterns, passing components as children, also remove much prop drilling.

How do you test that a page shows the right message when an API fails?

Frontend TestingEasy

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I would simulate failures at the network layer with Mock Service Worker or Playwright's page.route, returning 500 responses, timeouts or malformed JSON. Then I assert that the user sees a clear error message, a retry button works, and no broken partial data appears. Testing empty states and slow responses with loading indicators is equally important, because these paths are often skipped in manual testing.

What are long tasks and why do they hurt user experience?

Web PerformanceMedium

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A long task is any main-thread work lasting more than 50 milliseconds. While it runs, the browser cannot respond to taps or paint updates, so the page feels frozen. Common sources are large script evaluation, heavy JSON processing, big framework re-renders and third-party scripts. The Performance panel highlights them with red corners, and splitting work into smaller chunks or moving it to a worker keeps the page responsive.

A bug reached production even though all tests passed. What do you do next?

Frontend TestingEasy

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First I fix the bug and confirm the fix with the user's steps. Then I write a regression test that fails without the fix and passes with it, so the same bug cannot return. I also ask why existing tests missed it, for example mocks that hid the real API shape or a browser not covered, and improve that gap rather than only adding one test.

Define brand design tokens in Tailwind CSS v4.

CSS Architecture and AccessibilityMedium

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Tokens go in CSS with the @theme directive: @import 'tailwindcss'; @theme { --color-brand-500: #2563eb; --color-brand-700: #1d4ed8; --font-display: 'Poppins', sans-serif; --radius-card: 12px; } /* usage in markup */ /* <button class='bg-brand-500 hover:bg-brand-700 rounded-card font-display'> */ Tailwind generates utilities like bg-brand-500 from these variables and also exposes them as CSS custom properties for use in plain CSS.

What is visual regression testing?

Frontend TestingMedium

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Visual regression testing captures screenshots of pages or components and compares them pixel by pixel with approved baselines, flagging unexpected visual changes such as broken spacing or wrong colours. Tools include Playwright's toHaveScreenshot, Chromatic with Storybook and Percy. To avoid false failures, run in consistent containers, disable animations, and mask dynamic content like dates. It catches CSS bugs that functional tests miss.

How do you handle a situation where a bug you wrote affected users?

Frontend TestingEasy

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Situation: a form validation change I made blocked some users from signing up with valid numbers. Task: I needed to fix it and be transparent. Action: I informed my lead immediately, rolled back the change, found that my regex rejected numbers with a +91 prefix, fixed it, and added tests for different formats. Result: signups recovered within an hour, and I now test with real-world data samples.

How do you test code that depends on the current date or timers?

Frontend TestingMedium

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Real time makes tests slow and nondeterministic. I would use fake timers, such as vi.useFakeTimers() and vi.setSystemTime(new Date('2026-11-12T10:00:00+05:30')), then advance time with vi.advanceTimersByTime to test debounce, countdowns or expiry logic instantly. Restoring real timers after each test avoids leaking state. Designing functions to accept a clock or date parameter makes them even easier to test.

What are design tokens?

CSS Architecture and AccessibilityMedium

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Design tokens are named values for design decisions, such as color-primary, space-4 or radius-md, stored in one place and shared by designers and developers. They are often kept in JSON and converted into CSS custom properties, Tailwind theme values or mobile platform formats. Changing a token updates every component consistently, which makes rebranding or dark mode much easier than hunting hard-coded values.

How can you communicate between multiple tabs of the same site?

Browser APIsMedium

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BroadcastChannel lets same-origin tabs, windows and workers publish and subscribe to messages on a named channel, which suits syncing logout, theme or cart updates. The storage event fires in other tabs when localStorage changes, which is a simple fallback. SharedWorker can hold shared state for all tabs. Each option works only within the same origin, so cross-domain sync needs a server or postMessage.

Compare SPA, MPA, server-side rendering and static site generation.

Frontend ArchitectureEasy

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A single-page app loads once and renders views in the browser, giving app-like navigation but slower first load. A multi-page app renders each page on the server with full reloads. Server-side rendering generates HTML per request for fast content and SEO, then hydrates. Static site generation pre-builds HTML at build time and serves it from a CDN, which is fastest for content that changes rarely, like blogs.

What is the guiding principle of Testing Library and why query by role?

Frontend TestingMedium

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Testing Library encourages testing the way users interact: find elements by what they see and hear, not by implementation details like class names or component internals. getByRole('button', { name: 'Submit' }) is preferred because it also verifies the element is accessible. Tests written this way survive refactors and catch real accessibility problems. Test ids are a last resort when no accessible query works.

What are the URL and URLSearchParams APIs used for?

Browser APIsEasy

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The URL constructor parses a URL into parts like hostname, pathname and searchParams, and builds valid URLs without manual string concatenation. URLSearchParams reads and writes query strings, handling encoding automatically, for example params.get('page') or params.set('sort', 'price'). They prevent bugs with special characters such as spaces and ampersands in search terms, and are the clean way to sync filters with the address bar.

A new browser API you used does not work in older Safari versions. How do you handle it?

Browser APIsEasy

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I would use feature detection, such as if ('share' in navigator), rather than browser sniffing, and provide a fallback like a copy-link button. Checking Can I Use and the project's browser support list before building avoids surprises. Where reasonable, a small polyfill can fill gaps. This progressive enhancement approach ensures the core feature works everywhere while newer browsers get a better experience.

Detect offline status and retry queued requests when the connection returns.

Browser APIsMedium

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Listen for online and offline events and keep a small queue: const queue = []; async function send(req) { if (!navigator.onLine) { queue.push(req); showBanner('You are offline'); return; } await fetch(req.url, req.options); } window.addEventListener('online', async () => { hideBanner(); while (queue.length) await send(queue.shift()); }); window.addEventListener('offline', () => showBanner('You are offline')); navigator.onLine can report true on captive networks, so treat failed fetches as offline too. Persist the queue in IndexedDB for reliability.

Implement a throttle function.

Modern JavaScriptMedium

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Throttle allows a function to run at most once in a given interval: function throttle(fn, wait) { let last = 0; return function (...args) { const now = Date.now(); if (now - last >= wait) { last = now; fn.apply(this, args); } }; } window.addEventListener('scroll', throttle(updateProgressBar, 100)); Unlike debounce, which waits for calls to stop, throttle fires regularly during continuous events such as scrolling or dragging.

What are micro-frontends and when do they make sense?

Frontend ArchitectureHard

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Micro-frontends split a large web app into independently developed and deployed pieces, each owned by a team, composed at runtime with Module Federation, web components or server-side composition. They help large organisations where many teams block each other on one release. The costs are duplicated dependencies, inconsistent UX, complex shared state and harder performance tuning. For most teams, a well-structured monorepo is simpler.

What are generics and why are they useful?

TypeScriptMedium

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Generics let you write reusable code that keeps type information, using type parameters like <T>. For example, function first<T>(items: T[]): T | undefined returns a number for a number array and a User for a User array without losing types. Constraints such as <T extends { id: string }> restrict what T can be. Generics power typed API clients, form libraries and reusable UI components.

A third-party library you need has no TypeScript types. What do you do?

TypeScriptMedium

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First I check if types exist on DefinitelyTyped by installing @types/library-name. If not, I write a minimal declaration file, for example declare module 'old-chart-lib' with only the functions I use, in a types folder included by tsconfig. This is better than a blanket any import. If the library is important to the community, contributing those types upstream helps everyone.

Move a heavy calculation into a Web Worker.

Browser APIsMedium

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The worker runs on its own thread and talks through messages: // worker.js self.onmessage = (e) => { const total = e.data.reduce((sum, row) => sum + row.amount, 0); self.postMessage(total); }; // main.js const worker = new Worker(new URL('./worker.js', import.meta.url), { type: 'module' }); worker.postMessage(bigArrayOfRows); worker.onmessage = (e) => showTotal(e.data); The UI stays responsive. Data is copied between threads, so for huge binary data use transferable objects like ArrayBuffer.

What are source maps and should they be deployed to production?

Build Tools and ToolingEasy

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Source maps link minified production code back to the original source files and line numbers, so DevTools and error trackers show readable stack traces. They are generated by the bundler as .map files. Many teams upload them privately to monitoring tools like Sentry and do not serve them publicly, which keeps original source code less exposed while still allowing debugging of production errors.