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All IT interview question categories
HTML & CSS interview questions
What is responsive web design
CSS container queries
Responsive images: picture, srcset and sizes
CSS selector specificity
Html5 new features and apis
Semantic HTML
CSS position property
CSS grid layout
CSS z-index and stacking context
CSS-in-js problems and solutions
CSS logical properties
flexbox vs CSS grid comparison
CSS display property
What is the DOM?
Difference between script, async and defer
Web accessibility and ARIA attributes
CSS properties for creating animations and smooth transitions
CSS selectors
What is cascade in CSS
CSS functions: calc(), clamp(), min(), max()
CSS preprocessors: SASS, SCSS, and LESS
Methods for style isolation in CSS
Essential meta tags in HTML
Difference between strong and b tags in HTML
CSS clearing methods
What is doctype in HTML
CSS flexbox layout
CSS variables (custom properties)
Why transform is better for animations than top, left
CSS units: px, rem, em
CSS pseudo-classes and pseudo-elements
Why media queries are needed in CSS
CSS box-sizing property
What is BEM methodology (block element modifier)
How to hide elements visually but keep them accessible to screen readers
Block, inline and inline-block elements in HTML & CSS
Difference between visibility: hidden and display: none
HTML forms and built-in validation
What is margin collapsing in CSS
CSS aspect-ratio
CSS overflow property
CSS Object-fit and Object-position
CSS will-change property
What are vh, vw, vmin and vmax in CSS
What are data attributes in HTML
Difference between CSS reset and normalize
How to change color in svg file?
JavaScript interview questions
Event Loop: Microtasks vs Macrotasks
Prototypes and prototypal inheritance in JavaScript
Debounce and throttle in JavaScript
Closures in JavaScript
Call, apply and bind methods in JavaScript
Mutating and non-mutating Array methods in JavaScript
The this keyword in JavaScript
Type coercion in JavaScript (implicit vs explicit)
OOP in JavaScript (Object-oriented programming)
Spread and REST operators in JavaScript: differences and examples
Set, Map, WeakSet and WeakMap in JavaScript
Promises in JavaScript and promise methods
Execution context in JavaScript
Promise.all, promise.race, promise.allsettled, promise.any
Pure functions and side effects in JavaScript
What is temporal dead zone (TDZ) in JavaScript
Error handling: try/catch/finally in JavaScript
scope in JavaScript: types and working principles
Lexical environment in JavaScript
Event propagation in JavaScript and its phases
Difference between primitives and non-primitives in JavaScript
Optional chaining (?.) and nullish coalescing (??) in JavaScript
What is currying in JavaScript
callback functions and callback hell in JavaScript
What is Proxy Object in JavaScript
How can algorithm complexity be determined?
What is the call stack in JavaScript?
JavaScript modules: import/export, CommonJS vs es modules
Destructuring assignment in JavaScript
Memoization in JavaScript
Що не так з var у циклі та setTimeout?
Difference between null and undefined
Object.freeze(), object.seal() and object.assign() in JavaScript
What is IIFE (immediately invoked Function expression) in JavaScript
What is the difference between async/await and chaining?
What is idempotence?
WeakRef and finalizationregistry in JavaScript
Differences between arrow Function, Function declaration and Function expression
What is garbage collector in JavaScript?
What is code splitting?
Shallow copy vs deep copy in JavaScript
requestAnimationFrame and requestIdleCallback in JavaScript
Difference between event.preventdefault() and event.stoppropagation()
For...in vs for...of in JavaScript
Difference between in operator and hasOwnProperty() method in JavaScript
Why instanceof operator is needed in JavaScript
What is a polyfill?
What is symbol.iterator and why is it needed
What is arguments pseudo-Array in JavaScript
Boxing and unboxing in JavaScript
hoisting in JavaScript
Differences between var, let and const
Event delegation
What are higher-order functions in JavaScript (hof)
Json.parse and json.stringify in JavaScript
Template literals in JavaScript
Difference between event.target and event.currenttarget in JavaScript
The typeof operator in JavaScript
What are generators in JavaScript?
How to add a task to microtask queue with queueMicrotask
What is the difference between async and defer?
What is a dead letter queue?
What is async/await in JavaScript
How to copy an Object in JavaScript?
What is promise chaining in JavaScript
What is recursion?
Static methods in JavaScript
What is immutability?
What is the difference between Map and foreach in Array?
Data types in JavaScript
Loose (==) vs strict (===) equality in JavaScript
setTimeout and setInterval in JavaScript
How to GET all keys and values of Object in JavaScript
What is nan in JavaScript?
Strict mode in JavaScript
TypeScript interview questions
Conditional types in TypeScript
Type narrowing in TypeScript
Infer keyword in TypeScript — infer TypeScript
What is typeguard in TypeScript
Type assertions in TypeScript
Structural typing (duck typing) in TypeScript
What are mapped types in TypeScript
Discriminated unions in TypeScript
What is union in TypeScript
What does implements do in TypeScript?
Differences between type and interface in TypeScript
Differences between any and unknown in TypeScript
How keyof and typeof work in TypeScript
Never type in TypeScript
Utility type partial in TypeScript
The satisfies operator in TypeScript
Utility type awaited in TypeScript
What is generic in TypeScript
Why TypeScript is needed, pros and cons
What are decorators in TypeScript?
Index signatures and index access types in TypeScript
Utility type exclude in TypeScript
Function overloads in TypeScript
Utility type extract in TypeScript
Tuple types in TypeScript
Access modifiers in TypeScript: public, private, protected, readonly
Literal types in TypeScript
Utility type nonnullable in TypeScript
What is execution context?
Utility type record in TypeScript
Utility type pick in TypeScript
Utility type omit in TypeScript
Utility type returntype in TypeScript
What is an enum in TypeScript
Template literal types in TypeScript
Utility type readonly in TypeScript
Utility type parameters in TypeScript
Const assertions (as const) in TypeScript
Abstract classes in TypeScript
Declaration merging in TypeScript
Utility type required in TypeScript
What problem do hooks solve in React?
What is the n + 1 problem in GraphQL?
Intersection types in TypeScript
React interview questions
React fiber and virtual DOM update process
React.lazy And suspense — lazy components in React
React hydration and server-side rendering (SSR)
What is batching in React?
Reconciliation in React
How useEffect works in React?
How useState works in React?
Concurrent rendering in React
Refs in React (useRef, createref, forwardref)
Render props pattern in React
React performance optimization techniques
State management approaches in React
What is the difference between useCallback and useMemo?
What are custom hooks in React
What is React.memo and why is it needed
component rendering order and hook calling in React
How useLayoutEffect works in React and how does it differ from useEffect?
Error boundaries in React
useTransition and useDeferredValue in React
How useMemo works and why is it needed
React server components (rsc)
Rules for using hooks in React
Why is key needed in React?
What is JSX in React?
What is React and why is it needed?
What is prop drilling and how to avoid it
Synthetic events in React
What is AbortController?
What is the difference between useEffect and useLayoutEffect?
Virtual DOM in React
How useCallback works and why is it needed
Reasons for component re-rendering in React
component lifecycle methods in React
Controlled and uncontrolled components in React
Forms and form handling in React
What is useReducer in React?
What is HOC (higher-order component) in React
What is virtualization and why is it needed
Difference between functional and Class components in React
What is useSyncExternalStore in React?
React.StrictMode
Why useImperativeHandle is needed in React
What is React.PureComponent
What is a pure Function?
What is debounce?
What are WeakMap, WeakSet, and WeakRef?
What is context and useContext hook in React
Lifting state up in React
Composition vs inheritance in React
What is children in React
What is fragment in React
What is portal in React
What is useId hook in React?
What is memoization?
What is closure in js?
Immutability in React state
Next.js interview questions
Caching in Next.js
API routes (route handlers) in Next.js
App Router vs Pages Router in Next.js
How server components (rsc) work in Next.js
Server actions in Next.js
Parallel routes and intercepting routes in Next.js
Parallel and sequential data fetching in Next.js
Revalidation strategies in Next.js
Error handling in Next.js
Key features of Next.js
Layouts and templates in Next.js
Streaming and loading UI in Next.js
How incremental static regeneration (ISR) works in Next.js
How client-side rendering (CSR) works in Next.js
Internationalization (i18n) in Next.js
Deploying Next.js applications
Font optimization (next/font) in Next.js
Server and client component patterns in Next.js
Data fetching in Next.js
How server-side rendering (SSR) works in Next.js
Authentication patterns in Next.js
middleware in Next.js
Routing in Next.js (file-based routing)
How static site generation (SSG) works in Next.js
Dynamic routes and dynamic segments in Next.js
Image optimization (next/image) in Next.js
Metadata and SEO in Next.js
Next/link and navigation in Next.js
Edge runtime vs Node.js runtime in Next.js
What is Next.js and why use it
Configuring Next.js (next.config.js)
Route groups in Next.js
Environment variables in Next.js
Vue interview questions
Vue components and their lifecycles
Ref vs reactive in Vue.js
How does reactivity work in Vue.js?
Options API and composition API
Composables in Vue.js
Computed, methods and watchers in Vue.js
Pinia: state management in Vue.js
Vue router: routing and navigation guards
How does virtual DOM work in Vue.js?
Main directives in Vue.js
V-model in Vue.js
Provide/inject in Vue.js
defineProps, defineEmits, and defineExpose in Vue.js
What are props in Vue?
How to efficiently pass data between components?
What are slots in Vue?
Emits and custom events in Vue.js
async components and suspense in Vue.js
Custom directives in Vue.js
Keepalive in Vue.js
What is nexttick in Vue.js?
Dynamic components in Vue.js
What are attribute bindings in Vue?
Template refs in Vue.js
Error handling in Vue.js
Teleport in Vue.js
Transition and transitiongroup in Vue.js
How to add fallback content for slots in Vue?
Nuxt.js interview questions
What are rendering modes in Nuxt (SSR, SSG, SPA, Hybrid)?
What is the difference between useFetch and useAsyncData in Nuxt?
What is Nuxt.js and how does it differ from Vue.js?
What are composables in Nuxt?
How to manage state in Nuxt 3?
What is middleware in Nuxt and how to use it?
How to create API routes in Nuxt?
What are plugins in Nuxt?
What are layouts in Nuxt?
How do auto-imports work in Nuxt?
Angular interview questions
Advanced dependency injection patterns in Angular
Testing in Angular (unit and integration tests)
How does change detection work in Angular?
What is RxJS and how is it integrated in Angular?
component lifecycle methods in Angular
Services and dependency injection in Angular
What are directives and what types exist in Angular?
What is subject and what types of subjects exist in RxJS?
Angular router: routing, guards, and lazy loading
Signals in Angular
Common RxJS operators in Angular
Difference between template-driven and reactive forms in Angular
HttpClient and interceptors in Angular
Standalone components in Angular
What are modules in Angular and how are they used?
Injector hierarchy in Angular
What is ngzone in Angular?
What is Angular?
ViewChild and ContentChild in Angular
Data binding in Angular
@input and @output decorators in Angular
Content projection (ng-content) in Angular
Pipes in Angular (built-in and custom)
Difference between AngularJS and Angular
Redux interview questions
Redux vs context API
Redux toolkit
What is RTK Query in Redux Toolkit?
What are selectors in Redux?
Redux Thunk vs Redux Saga - what is the difference?
What is Redux?
Redux middleware
Node.js interview questions
What is libuv and how does it enable async i/o in Node.js?
What is error-first callback pattern?
What are the key security best practices in Node.js?
How the Event Loop works in Node.js
What are streams in Node.js?
What are child processes in Node.js?
What is PM2 and how to manage Node.js processes in production?
Synchronous vs asynchronous code in Node.js
Error handling patterns in Node.js
CommonJS vs es modules in Node.js
What is middleware in Express.js and how does it work?
What is the cluster module in Node.js?
What are worker threads in Node.js?
What is eventemitter in Node.js?
What is a buffer in Node.js?
How does Garbage Collection work in Node.js (V8)?
How does the File System (fs) module work in Node.js?
How does the HTTP module work in Node.js?
What is Node.js and how does it work?
How to work with environment variables in Node.js?
What is package.json and how does npm work?
What is package-lock.json?
What is the difference between promise.all and promise.allsettled?
What is promisification?
What is the difference between process.nextTick() and setImmediate()?
How to detect and prevent memory leaks in Node.js?
What are the most common design patterns in Node.js?
How to use the Crypto module in Node.js for hashing and encryption?
How do Timers and scheduling work in Node.js?
Express.js interview questions
What is middleware in Express.js and how does it work?
How to serve static files and improve performance in Express.js?
How to implement JWT authentication in Express.js?
How to build a REST API with Express.js?
What is CORS and how to configure it in Express.js?
How to handle errors in Express.js?
How to secure an Express.js application?
How to handle async/await in Express.js route handlers?
How to validate request data in Express.js?
How to structure a large Express.js application?
What is Express router and how to use it for modular routing?
How to test an Express.js application?
What is Express.js and why is it used?
What are the req and res objects in Express.js?
Route parameters and query strings in Express?
How does body parsing work in Express.js?
How to use template engines in Express.js?
What are the different types of middleware in Express.js?
How does session management work in Express.js?
How to handle file uploads in Express.js with Multer?
How to implement logging in Express.js (Morgan, Winston)?
How to implement API versioning in Express.js?
How to implement caching in Express.js for better performance?
How to integrate WebSocket with Express.js?
Express.js vs Fastify vs Koa — which to choose?
What are the best database integration patterns in Express.js?
How to optimize Express.js application performance?
NestJS interview questions
What is middleware in NestJS and how does it differ from guards?
How to implement caching strategies in NestJS?
What are providers and how does dependency injection work in NestJS?
What are lifecycle hooks in NestJS?
How do Microservices work in NestJS?
What are Dynamic Modules in NestJS and when to use them?
What are guards in NestJS and how to implement authentication?
What are dtos and how does validation work in NestJS?
What are interceptors in NestJS?
What are modules in NestJS and how do they work?
What are pipes in NestJS?
What are exception filters in NestJS?
What is NestJS and what problems does it solve?
How does NestJS integrate with TypeORM?
What are controllers in NestJS?
How to test a NestJS application?
How to manage configuration in NestJS with configmodule?
How to document a NestJS API with Swagger?
How to create and use custom decorators in NestJS?
How to implement WebSocket Gateways in NestJS?
What is CQRS pattern and how to implement it in NestJS?
How to implement queue processing with Bull in NestJS?
How to implement authentication with Passport in NestJS?
How to build a GraphQL API with NestJS?
How to implement Role-Based Access Control (RBAC) in NestJS?
Git interview questions
What is git stash and when to use it?
Difference between git reset and git revert?
What is git cherry-pick and when to use it?
What is the difference between git fetch and git pull?
What is the difference between git merge and git rebase?
Git branching strategies (Git Flow, GitHub Flow)?
How to resolve merge conflicts in Git?
What are Git hooks?
What are Git tags and when to use them?
What is git bisect?
Architecture interview questions
Microfrontend architecture
What is the CAP theorem?
Feature-sliced design (FSD). must-know frontend architecture
REST API design principles and best practices?
What is MVC architecture pattern?
What is Microservices architecture?
Modular architecture
Atomic design architecture
Monorepo vs Polyrepo - pros and cons?
What is a circuit breaker?
Principles interview questions
SOLID principles
What is Single Responsibility Principle (SRP)?
DRY (don't repeat yourself)
What is Open-Closed Principle (OCP)?
What is Liskov Substitution Principle (LSP)?
KISS (keep it simple, stupid)
YAGNI (you aren't gonna need it)
Patterns interview questions
MVC (model-view-controller) and MVP (model-view-presenter) design patterns
What is Proxy design pattern?
Abstract factory pattern
What are grasp patterns
Observer pattern
Singleton pattern
What is Factory design pattern?
decorator pattern
What is Strategy design pattern?
What is Adapter design pattern?
What is Module design pattern?
What is Command design pattern?
General Questions interview questions
How to debug application and find memory leaks
What is the difference between functions and procedures in SQL?
CSR, SSR, SSG, ISR — difference between rendering strategies
What is critical rendering path (crp) in browser
ACID - atomicity
ACID - consistency
Ways to optimize applications
OWASP browser vulnerabilities
What are composite indexes?
Browser storage: cookie, LocalStorage, SessionStorage and IndexedDB
When reflow and repaint occur in browser
What is WebSocket and how does it work?
What is service worker?
How browser works when entering request and rendering stages
Modern browser architecture (processes and threads)
Server-sent events, polling and long polling: what they are and when to use
Resource loading strategies - preload, prefetch, modulepreload
What is three-way handshake?
What are symmetric and asymmetric keys in encryption?
What is CORS and how does it work?
HTTP status codes
What is REST and REST principles — REST API
What is the difference between authorization and authentication?
How HTTPS works and difference from HTTP
How HTTP works and what an HTTP request consists of
What is JWT and how does it work?
What is CSRF and how to prevent it?
What is XSS and how to prevent it?
Types of frontend testing
V8 architecture: from code to machine instructions
Parsing pipeline - from bytes to DOM and CSSOM
HTTP/2 vs HTTP/3: protocol evolution
Immutability and mutability in JavaScript
What are web workers?
What is CDN and why is it needed?
What is the difference between PUT and PATCH?
How does left join work?
What are clustered and non-clustered indexes?
What is Webpack?
What is the difference between process and thread in Node.js?
What is progressive rendering in web development
What is shadow DOM in web development
Can you send a body in a GET request?
How does right join work?
What are referential actions in SQL?
What is throttling?
What are noisy tenants?
Docker interview questions
What is Docker and why do we need it?
How to set up a health check for a Docker container?
Container vs Virtual Machine: what is the difference?
What are the main components of Docker architecture?
Docker daemon and Docker client: how do they interact?
How to push and pull images on Docker Hub?
Docker layers and Union File System explained
Docker registry vs Docker Hub: what is the difference?
What is a Docker container?
What is a Docker image?
What is a Dockerfile?
What are dangling Docker images and how to remove them?
What is the Docker container lifecycle?
Docker volume vs bind mount: what is the difference?
CMD vs ENTRYPOINT in Dockerfile: what is the difference?
COPY vs ADD in Dockerfile: what is the difference?
How to get inside a running Docker container?
Zero-downtime deployment approaches with Docker
Immutable infrastructure with Docker explained
How to inspect container state, logs, and metadata?
How to live migrate a Docker container between hosts using CRIU?
How to organize log management in Docker?
What are Docker Compose profiles and how to use them?
How to list running and all Docker containers?
How to fix 'no space left on device' on a Docker host?
How to implement Docker container security hardening?
How to run a container from a Docker image?
How to troubleshoot network problems between Docker containers?
What is the overlay2 storage driver and when to change it?
How to build multi-platform Docker images (ARM + AMD64)?
How to handle signals in containers and what is the init process?
How to stop and remove a Docker container?
What is Docker Compose?
How to set up a private Docker registry with Harbor?
What is rootless Docker and when to use it?
What is a Docker volume and why do you need it?
What is Docker Content Trust (DCT)?
What is BuildKit and what advantages does it provide?
What is containerd and its role in the Docker ecosystem?
How to debug problems in a Docker container?
What are distroless images and what advantages do they offer?
How to scan Docker images for vulnerabilities?
How does Docker bridge networking work?
How to manage secrets (passwords, keys) in Docker properly?
How to perform a rolling update in Docker Swarm?
How to use Docker in a CI/CD pipeline?
docker exec vs docker attach: what is the difference?
How to implement blue-green deployment with Docker?
What is .dockerignore and why do you need it?
What is Docker Swarm?
What are Docker labels and what are they used for?
How does Docker build cache work and how to manage it?
How to update a Docker container without losing data?
How to share data between Docker containers?
How to monitor Docker containers in production?
How to inspect Docker image metadata?
docker stop vs docker kill: what is the difference?
How to transfer Docker images between hosts without a registry?
What are Linux namespaces and cgroups in Docker?
How to use environment variables in Docker?
How to copy files between a Docker container and the host?
How to scale services in Docker Compose?
How to create a Docker image from a running container?
Where are Docker volumes stored on the host?
How to reduce the size of a Docker image?
EXPOSE in Dockerfile vs port publishing: what is the difference?
What is a Docker restart policy and what options exist?
What is a Docker overlay network and when do you need it?
How do containers communicate in Docker Compose?
How does Docker networking work and what network types exist?
What is a multi-stage Docker build and why use it?
How to limit container CPU and memory resources?
How to manage service dependencies in Docker Compose?