#Javascript

Last updated    - V4 (13-Sep-2025)

Level Topic Subtopics Basic Introduction History of JavaScript, ECMAScript, JavaScript Engines, Running JavaScript, Use Cases Variables & Data Types var, let, const, Primitive Types, Reference Types, Type Coercion Operators Arithmetic, Comparison, Logical, Assignment, Ternary Control Flow if/else, switch, for, while, do-while, break & continue Functions Function Declaration, Function Expression, Arrow Functions, Default Parameters, Rest/Spread Intermediate Objects & Arrays Object Creation, Array Methods (map, filter, reduce), Destructuring, Spread/Rest, Object.assign Scope & Hoisting Global Scope, Function Scope, Block Scope, Variable Hoisting, Function Hoisting Closures Definition, Lexical Scope, Practical Use Cases, Module Pattern, Private Variables DOM Manipulation Selecting Elements, Creating Elements, Event Handling, Class Manipulation, DOM Traversal Asynchronous JS Callbacks, Promises, async/await, Event Loop, Microtasks vs Macrotasks Advanced Prototypes & Inheritance Prototype Chain, proto, Object.create, Class Syntax, Inheritance Patterns Advanced Functions Higher-Order Functions, Currying, Memoization, Partial Application, Function Composition Error Handling try/catch/finally, Error Object, Custom Errors, Error Propagation, Debugging Modules ES6 Modules (import/export), CommonJS, AMD, UMD, Dynamic Imports Event Handling Model Event Bubbling, Event Capturing, Delegation, Passive Listeners, Custom Events Expert Performance & Optimization Memory Management, Garbage Collection, Event Loop Optimization, Debouncing & Throttling, Lazy Loading Design Patterns Singleton, Factory, Observer, Module, Revealing Module Security in JS XSS Prevention, CSP, Sanitization, CORS, Secure Coding Practices Advanced Async Patterns Generators, Iterators, Observables, Web Workers, Service Workers JavaScript in Modern Apps ESNext Features, TypeScript with JS, WebAssembly, Micro-Frontends, Edge Computing

1. Basics & Fundamentals

1. What is JavaScript and how is it different from Java?
2. Explain the difference between ES5 and ES6.
3. What are variables in JavaScript?
4. Differentiate between var, let, and const.
5. What are primitive data types in JavaScript?
6. What are reference types in JavaScript?
7. Explain type coercion in JavaScript.
8. What is the difference between == and ===?
9. What are template literals in ES6?
10. What is the typeof operator?
11. How do you check if a variable is an array?
12. What is NaN in JavaScript?
13. What is the difference between null and undefined?
14. How do you convert a string to a number in JavaScript?
15. What are truthy and falsy values?
16. What is the difference between implicit and explicit type conversion?
17. What is hoisting in JavaScript?
18. How does variable shadowing work?
19. What is the difference between block scope and function scope?
20. Explain the concept of scope chain.
21. What is the difference between shallow copy and deep copy?
22. How do you clone an object in JavaScript?
23. What is the difference between pass by value and pass by reference?
24. What are reserved keywords in JavaScript?
25. What is the difference between synchronous and asynchronous execution?

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2. Functions

1. What is a function in JavaScript?
2. Differentiate between function declaration and function expression.
3. What are arrow functions and how are they different?
4. What are higher-order functions?
5. What is a callback function?
6. Explain function currying with an example.
7. What are default parameters in functions?
8. What is the rest parameter in ES6?
9. What is the spread operator in functions?
10. Explain recursion in JavaScript.
11. What is the difference between pure and impure functions?
12. How do you memoize a function?
13. What is the difference between call, apply, and bind?
14. How do you implement function overloading in JavaScript?
15. Explain the concept of closures.
16. What are immediately invoked function expressions (IIFE)?
17. What is function hoisting?
18. Explain anonymous functions in JavaScript.
19. What are generator functions?
20. Explain async functions in JavaScript.
21. What is tail call optimization?
22. How do you debounce a function?
23. How do you throttle a function?
24. What is the difference between named and anonymous functions?
25. How does the this keyword behave in functions?

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3. Objects & Arrays

1. What are objects in JavaScript?
2. How do you create an object in JavaScript?
3. What is object destructuring?
4. What are object methods in ES6?
5. Explain the difference between Object.seal and Object.freeze.
6. What are object prototypes?
7. How do you check if an object has a property?
8. How do you loop through object properties?
9. What are computed property names?
10. What is Object.assign used for?
11. Explain the difference between Map and Object.
12. What is a WeakMap?
13. What is a WeakSet?
14. What is the difference between Set and Array?
15. What are array methods like map, filter, reduce?
16. Explain the difference between forEach and map.
17. How do you flatten a nested array in JavaScript?
18. What is array destructuring?
19. How do you remove duplicates from an array?
20. How do you merge two arrays in JavaScript?
21. What is the difference between slice and splice?
22. How do you find the maximum value in an array?
23. What is the difference between find and filter?
24. What are array-like objects?
25. What is the difference between mutable and immutable objects?

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4. DOM Manipulation

1. What is the DOM?
2. How do you select an element by ID in JavaScript?
3. How do you select elements by class name?
4. What is the difference between querySelector and querySelectorAll?
5. How do you create an element in JavaScript?
6. How do you append a child element?
7. How do you remove a DOM element?
8. What is innerHTML vs textContent?
9. How do you change the style of an element dynamically?
10. What are DOM events?
11. What is the difference between inline, inline-block, and block elements?
12. What is event bubbling in JavaScript?
13. What is event capturing in JavaScript?
14. How do you use event delegation?
15. What is the difference between addEventListener and onclick?
16. How do you trigger a click event programmatically?
17. How do you prevent the default behavior of an event?
18. What is stopPropagation in JavaScript?
19. How do you handle form validation with JavaScript?
20. How do you dynamically create and add CSS classes?
21. How do you toggle a class on an element?
22. How do you implement drag-and-drop in JavaScript?
23. How do you detect when the DOM is fully loaded?
24. What is the difference between DOMContentLoaded and load events?
25. How do you manipulate attributes of a DOM element?

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5. Asynchronous JavaScript

1. What is asynchronous programming in JavaScript?
2. What is a callback function?
3. What is the difference between synchronous and asynchronous code?
4. What is the event loop in JavaScript?
5. What are microtasks and macrotasks?
6. Explain the difference between setTimeout and setInterval.
7. What is Promise in JavaScript?
8. What are the states of a Promise?
9. What is the difference between resolve and reject?
10. How do you chain promises?
11. What is Promise.all?
12. What is Promise.race?
13. What is Promise.any?
14. What is Promise.allSettled?
15. What are async/await keywords?
16. How do you handle errors in async/await?
17. What is the difference between async and defer in script tags?
18. What is callback hell?
19. How do you avoid callback hell?
20. What are generators in JavaScript?
21. What are Observables?
22. What are Web Workers?
23. What is the Fetch API?
24. How does Axios differ from Fetch?
25. What is JSON and how is it used in async calls?

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6. Scope, Execution & Closures

1. What is lexical scope in JavaScript?
2. What is the scope chain?
3. What is the difference between global and local scope?
4. What is block scope?
5. What is function scope?
6. Explain execution context in JavaScript.
7. What are phases of execution context?
8. What is variable environment?
9. Explain closure with an example.
10. What are use cases of closures?
11. What is the difference between closure and scope?
12. How do closures help in data hiding?
13. What is the difference between module pattern and closures?
14. What are memory leaks in closures?
15. What is temporal dead zone (TDZ)?
16. What is strict mode in JavaScript?
17. What happens if you forget var/let/const in strict mode?
18. What is the difference between this inside arrow function and normal function?
19. How does this keyword behave in different scopes?
20. What is globalThis?
21. What is eval in JavaScript?
22. Why is eval discouraged?
23. How do closures help in implementing currying?
24. How do you implement a private counter with closures?
25. What is the difference between closure and garbage collection?

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7. Prototypes & OOP

1. What is prototype in JavaScript?
2. What is the prototype chain?
3. What is proto in JavaScript?
4. How do you implement inheritance using prototypes?
5. What is the difference between prototype and class in ES6?
6. How do you define a class in ES6?
7. What are class fields in ES6?
8. What are static methods in classes?
9. What is the difference between constructor and class methods?
10. How do you extend a class in ES6?
11. What is super() keyword?
12. What is encapsulation in JavaScript?
13. What is polymorphism in JavaScript?
14. What is abstraction in JavaScript?
15. What is the difference between composition and inheritance?
16. What are mixins in JavaScript?
17. What is method chaining in JavaScript?
18. What is the difference between ES6 classes and function constructors?
19. How do you create a singleton object in JavaScript?
20. What are private fields in ES2022?
21. What are getters and setters in classes?
22. How do you override methods in JavaScript?
23. What is multiple inheritance in JavaScript?
24. What is the difference between instanceof and typeof?
25. How do you check if an object is created from a specific class?

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8. Error Handling & Debugging

1. What is error handling in JavaScript?
2. What is the difference between syntax error and runtime error?
3. What is try-catch-finally in JavaScript?
4. How do you throw custom errors?
5. What are error objects in JavaScript?
6. What is stack trace in errors?
7. How do you handle asynchronous errors?
8. What is the difference between onerror and addEventListener('error')?
9. What is the difference between console.log, console.error, and console.warn?
10. How do you use console.table?
11. What is the difference between debugger statement and console.log?
12. How do you use breakpoints in browser DevTools?
13. How do you debug promises?
14. How do you debug async/await functions?
15. How do you monitor network requests in JavaScript?
16. What are uncaught exceptions?
17. What are unhandled promise rejections?
18. How do you handle global errors?
19. How do you implement error boundaries in frontend apps?
20. What is try...finally without catch?
21. How do you create custom error classes?
22. How do you differentiate between operational and programmer errors?
23. What is strict mode?s effect on errors?
24. How do you log errors in production?
25. What are common debugging tools for JavaScript?

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9. Advanced Topics

1. What are JavaScript modules?
2. What is the difference between CommonJS and ES6 modules?
3. What is dynamic import in JavaScript?
4. What is tree-shaking in JavaScript bundlers?
5. What is memoization in JavaScript?
6. How do you implement caching in JavaScript?
7. What is an EventEmitter?
8. What is reactive programming in JavaScript?
9. What are promises vs observables?
10. What is the difference between synchronous iteration and asynchronous iteration?
11. What are WebSockets?
12. How do you implement pub-sub in JavaScript?
13. What is service worker in JavaScript?
14. What is push notification API?
15. What are streams in JavaScript?
16. How do you use fetch with streams?
17. What is WebRTC?
18. What are shared workers?
19. How does JavaScript handle concurrency?
20. What are atomics in JavaScript?
21. What is the difference between BigInt and Number?
22. What is Intl API in JavaScript?
23. How do you internationalize a JavaScript app?
24. What is Proxy in JavaScript?
25. What is Reflect API?

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10. Performance & Best Practices

1. How do you improve JavaScript performance?
2. What is debouncing and how do you implement it?
3. What is throttling and how do you implement it?
4. How do you optimize loops in JavaScript?
5. What is lazy loading in JavaScript?
6. How do you use requestAnimationFrame?
7. What is the difference between localStorage, sessionStorage, and cookies?
8. How do you use IndexedDB in JavaScript?
9. How do you handle memory leaks in JavaScript?
10. What is garbage collection in JavaScript?
11. How do you profile JavaScript performance?
12. What is the difference between minification and compression?
13. How do you use Web Workers for performance?
14. How do you handle long-running tasks in JavaScript?
15. What is event delegation?s role in performance?
16. What are best practices for writing maintainable JavaScript code?
17. How do you structure large-scale JavaScript applications?
18. What is code splitting in modern bundlers?
19. How do you optimize bundle size in JavaScript apps?
20. What is tree-shaking in bundlers like Webpack?
21. How do you optimize React/Angular apps using JavaScript?
22. How do you secure JavaScript code in frontend apps?
23. What is CSP and how does it help security?
24. How do you handle performance bottlenecks in SPAs?
25. What are common pitfalls to avoid in JavaScript?

#AVRO

Question count - 0     Last updated    - V4 (28-Aug-2024)

What is Apache Avro?

State some Key Points about Apache Avro?

What Avro Offers?

Who is intended audience to Learn Avro?

What are prerequisites to learn Avro?

Explain Avro schemas?

Explain Thrift and Protocol Buffers and Avro?

Why Avro?

How to use Avro?

Name some primitive types of Data Types which Avro Supports.

Name some complex types of Data Types which Avro Supports.

What are best features of Apache Avro?

Explain some advantages of Avro.

Explain some disadvantages of Avro.

What do you mean by schema declaration?

Explain the term Serialization?

What do you mean by Schema Resolution?

Explain the Avro Sasl profile?

What is the way of creating Avro Schemas?

Name some Avro Reference Apis?

When to use Avro?

Explain sort order in brief?

What is the advantage of Hadoop Over Java Serialization?

What are the disadvantages of Hadoop Serialization?

AVRO
Question	Option A	Option B	Option C	Option D

#BSON

Question count - 0     Last updated    - V4 (07-Aug-2024)

BSON
Question	Option A	Option B	Option C	Option D

#OpenAPI (Swagger)

Question count - 0     Last updated    - V4 (19-Feb-2025)

What is Swagger?

What is API?

What is API Definition and why to create it?

What is the purpose of an API definition?

What happens when I publish the API in SwaggerHub?

What are the integrations that are available in SwaggerHub?

What is meant by API Testing?

What is meant by Request Body?

What is meant by Response?

What about Dictionaries, Hashmaps, and Associative arrays?

Explain Documentation in Swagger.

Explain Structured Data Formats.

Explain the term Path?

Explain the term Operations?

Explain about parameters and types of parameters.

Explain Parameter Serialization.

Explain the term Schema.

Explain Data Models.

Explain the Swagger data types.

Explain about Enums.

Explain Authentication and Authorization.

Why use OpenAPI?

How does the Web API work?

How does SwaggerHub help with documenting my API?

How do I mock an API backend Server?

#TypeScript

Question count - 0     Last updated    - V4 (02-Sep-2024)

What are Ambients in TypeScripts and when to use them?

What are different components of TypeScript?

What are Modules in Typescript?

What are the benefits of TypeScript?

What are the difference beetween Typescript and JavaScript?

What is "Decorators" in TypeScript?

What is a TypeScript Map file?

What is getters/setters in TypeScript?

What is Interface in TypeScript?

What is one thing you would change about TypeScript?

What is the default access modifier for members of a class in TypeScript?

What is the difference between "interface vs type" statements?

What is the difference between Classes and Interfaces in Typescript?

What is TypeScript and why do we need it?

What is Typescript and why one should use it?

What is TypeScript and why would I use it in place of JavaScript?

What is Typings in Typescript?

Explain generics in TypeScript

Explain how and why we could use property decorators in TS?

Explain when to use "declare" keyword in TypeScript

Explain why that code is marked as WRONG?

Which object oriented terms are supported by TypeScript?

How can you allow classes defined in a module to accessible outside of the module?

How could you check null and undefined in TypeScript?

How to call base class constructor from child class in TypeScript?

How to implement class constants in TypeScript?

How To Use external plain JavaScript Libraries in TypeScript?

How TypeScript is optionally statically typed language?

How would you overload a class constructor in TypeScript?

When to use interfaces and when to use classes in TypeScript?

Are strongly-typed functions as parameters possible in TypeScript?

Could we use TypeScript on backend and how?

Do we need to compile TypeScript files and why?

Does TypeScript support all object oriented principles?

Does TypeScript supports function overloading?

Is it possible to generate TypeScript declaration files from JS library?

Is that TypeScript code valid? Explain why.

List the built-in types in Typescript

What's wrong with that code?

TypeScript - Types (string, number, boolean, etc.), Type Annotations (variables, function parameters, and return types) TypeScript Compiler Strict mode Type Assignment - Explicit, Implicit Special Types - Type: any , Type: unknown, Type: never, Type: undefined & null Primitive types Dynamic types & Literal types Classes - Members: Types, Members: Visibility, Parameter Properties, Readonly Inheritance - Inheritance: Implements, Inheritance: Extends, Override, Abstract Classes Objects

Arrays - Readonly, Type Inference Tuples - Typed Arrays, Readonly Tuple, Named Tuples, Destructuring Tuples Object Types - Type Inference, Optional Properties, Index Signatures Enums - Numeric Enums (With Default, With Initialized, Fully Initialized), String Enums Functions - Return Type, Void Return Type, Parameters (Optional Parameters, Default Parameters, Named Parameters, Rest Parameters) The DOM and type casting - Casting with as, Casting with <>, Force casting Narrowing Interfaces - Extending Interfaces Type Aliases - Union | (OR), Union Type Errors Union and Intersection Types

Type Inference Type Assertions Generics Modules Decorators TypeScript Configuration TypeScript Null & Undefined Null - Optional Chaining, Nullish Coalescence, Null Assertion, Array bounds handling Keyof - keyof with explicit keys, keyof with index signatures

TypeScript
Question	Option A	Option B	Option C	Option D
Which of the following is a correct way to declare a variable in TypeScript?	let varName: type;	var varName = type;	let varName = type;	varName: type;
What is the default access modifier in TypeScript?	public	private	protected	internal
Which of the following is used to specify the types of function parameters and return type in TypeScript?	type()	typeof()	functionType()	(): type

#ReactJS

Last updated    - V4 (13-Sep-2025)

Level Topic Subtopics Basic Introduction What is React, Features of React, Advantages over other frameworks, Virtual DOM, JSX Components Functional Components, Class Components, Props, Default Props, PropTypes State Management useState Hook, Class Component State, setState(), Initial State, State vs Props Rendering Conditional Rendering, Lists & Keys, Rendering Arrays, Fragments, Inline Rendering Events Handling Events, Synthetic Events, Event Binding, Passing Arguments, Event Bubbling Intermediate Hooks useEffect, useContext, useRef, useMemo, useCallback Forms Controlled Components, Uncontrolled Components, Form Validation, useForm Libraries Routing React Router Basics, Route Parameters, Nested Routes, Redirects, Protected Routes Styling CSS Modules, Styled Components, Emotion, Inline Styles, Tailwind with React Context API Creating Context, useContext Hook, Context vs Redux, Context Performance, Nested Contexts Advanced State Management Redux, Redux Toolkit, Middleware (Thunk, Saga), Zustand, Recoil Performance Optimization Memoization, React.memo, Code Splitting, Lazy Loading, Suspense Server-Side Rendering Next.js Basics, Static Site Generation (SSG), Incremental Static Regeneration (ISR), SSR vs CSR, Hydration Testing Jest, React Testing Library, Enzyme, Snapshot Testing, Mocking APIs Error Handling Error Boundaries, try-catch in async calls, Fallback UI, Logging Errors, Monitoring Expert Architecture & Patterns Higher-Order Components (HOC), Render Props, Compound Components, Custom Hooks, Controlled vs Uncontrolled Patterns Advanced Performance React Concurrent Mode, Suspense for Data Fetching, React Profiler, Optimization with Webpack, Tree Shaking Scalability Monorepos with React, Micro-Frontends, Module Federation, Large-Scale Folder Structures, Design Systems Integrations GraphQL with React (Apollo, Relay), WebSockets, WebRTC, REST APIs, gRPC Deployment & CI/CD Dockerizing React Apps, CI/CD Pipelines, Hosting (Vercel, Netlify, AWS Amplify), Performance Budgets, SEO Optimization

1. Components

1. What are React components?
2. Differentiate between functional and class components.
3. What is JSX and why is it used in React?
4. How do you pass data from parent to child components?
5. What are default props in React?
6. How do you validate props in React?
7. What is the difference between props and state?
8. Explain component lifecycle methods in class components.
9. What is the difference between controlled and uncontrolled components?
10. How do you conditionally render components in React?
11. What are fragments and why are they used?
12. How do you render lists in React?
13. What is the significance of keys in lists?
14. Explain React.memo and its use cases.
15. How do you share data between sibling components?
16. What are Higher-Order Components (HOC)?
17. Differentiate between smart and dumb components.
18. What are render props in React?
19. How do you optimize re-rendering in React components?
20. What is the difference between PureComponent and React.Component?
21. How do you handle errors in React components?
22. What are portals in React?
23. Explain lazy loading of components.
24. How do you structure a large React project?
25. What are compound components?

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2. Hooks

1. What are React hooks?
2. Explain the useState hook with an example.
3. How does useEffect work in React?
4. Differentiate between useEffect and componentDidMount.
5. What are rules of hooks in React?
6. What is useContext hook and how is it used?
7. Explain the useReducer hook with an example.
8. What is the difference between useCallback and useMemo?
9. What is the useRef hook used for?
10. How do you build custom hooks in React?
11. Explain performance optimizations with useMemo.
12. What is the difference between controlled and uncontrolled forms with hooks?
13. How can you clean up side effects in useEffect?
14. What is the difference between useLayoutEffect and useEffect?
15. How do you fetch data using hooks?
16. Explain how hooks replace lifecycle methods.
17. What is the useImperativeHandle hook?
18. How do you handle global state with hooks?
19. Explain batching of state updates with hooks.
20. What are stale closures in hooks?
21. How do you debounce input using hooks?
22. Explain polling with useEffect.
23. What is the difference between useId and useRef?
24. What are hook dependency arrays?
25. Explain pitfalls of hooks and how to avoid them.

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3. State Management

1. What is state in React?
2. Differentiate between local and global state.
3. What are the drawbacks of prop drilling?
4. Explain Context API for state management.
5. How do you use Redux with React?
6. What are reducers in Redux?
7. Explain actions and action creators in Redux.
8. What is Redux Toolkit?
9. How does middleware work in Redux?
10. Explain Redux Saga with an example.
11. What is Zustand and when to use it?
12. Differentiate between Redux and MobX.
13. What are selectors in Redux?
14. How do you persist Redux state?
15. Explain Recoil for state management.
16. How do you manage asynchronous state in Redux?
17. What is the difference between Flux and Redux?
18. What are effects in Redux Thunks vs Sagas?
19. How do you debug Redux apps?
20. What are best practices for managing state in large apps?
21. Explain the concept of immutable state updates.
22. How do you structure Redux store?
23. What are atoms in Recoil?
24. How does Zustand differ from Redux?
25. When should you avoid Redux?

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4. Routing

1. What is React Router?
2. How do you install and configure React Router?
3. Explain BrowserRouter and HashRouter.
4. What is the difference between Link and NavLink?
5. How do you handle dynamic routing in React?
6. Explain route parameters with examples.
7. What are nested routes in React Router?
8. How do you implement redirects?
9. Explain protected routes in React.
10. How do you handle authentication in routing?
11. What is the use of useNavigate hook?
12. Explain the useLocation hook.
13. What is the difference between Switch and Routes?
14. How do you handle 404 routes in React Router?
15. Explain lazy loading routes.
16. How do you handle query parameters in React Router?
17. What is the difference between exact and strict in routing?
18. How do you animate route transitions?
19. Explain useHistory hook in older React Router.
20. What is outlet in nested routes?
21. How do you protect routes with JWT authentication?
22. Explain MemoryRouter use cases.
23. How do you integrate Redux with React Router?
24. What is server-side routing vs client-side routing?
25. Explain hash-based routing.

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5. Performance Optimization

1. What is reconciliation in React?
2. How does the virtual DOM improve performance?
3. What is React Fiber?
4. How do you optimize re-renders in React?
5. Explain React.memo and PureComponent.
6. What is code splitting in React?
7. How do you implement lazy loading?
8. Explain dynamic imports in React.
9. What is tree shaking in React apps?
10. How do you measure React performance?
11. What is React Profiler?
12. How do you optimize large lists in React?
13. Explain windowing with react-window or react-virtualized.
14. How do you cache expensive calculations?
15. What are Web Workers and how can React use them?
16. Explain Suspense for data fetching.
17. How do you batch state updates in React?
18. Explain hydration in React SSR.
19. How do you optimize React context performance?
20. What is concurrent rendering?
21. How do you minimize bundle size?
22. Explain service workers for caching React apps.
23. How do you improve time-to-interactive in React apps?
24. What is Reselect in Redux?
25. How do you prevent memory leaks in React?

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6. Forms & Validation

1. What are controlled components in forms?
2. What are uncontrolled components in forms?
3. How do you use useState for form inputs?
4. Explain form validation in React.
5. How do you handle multiple inputs in a form?
6. What is the difference between controlled vs uncontrolled form validation?
7. Explain useForm hook from React Hook Form.
8. How do you integrate Formik in React?
9. How do you handle async validation in forms?
10. What are custom form hooks?
11. How do you reset form values?
12. How do you handle checkbox and radio inputs in forms?
13. Explain nested forms in React.
14. How do you handle file uploads in forms?
15. What is the role of useRef in uncontrolled forms?
16. How do you manage form state globally?
17. How do you handle conditional form fields?
18. What is form serialization?
19. How do you integrate Yup with Formik?
20. Explain debounce validation in forms.
21. How do you show error messages in forms?
22. How do you disable a submit button conditionally?
23. What is optimistic UI in forms?
24. How do you implement dynamic forms?
25. How do you test form components?

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7. Testing

1. What are the different testing levels in React?
2. How do you test React components with Jest?
3. What is React Testing Library?
4. How do you render a component in tests?
5. How do you simulate user events in testing?
6. What are snapshot tests in React?
7. How do you mock API calls in tests?
8. Explain mocking hooks in React tests.
9. How do you test asynchronous code in React?
10. What is shallow rendering in Enzyme?
11. How do you test props in React components?
12. How do you test state updates in React?
13. What is the difference between integration and unit tests?
14. How do you test context-based components?
15. How do you test React Router components?
16. What are mock functions in Jest?
17. How do you test Redux-connected components?
18. How do you use Cypress for E2E testing in React?
19. How do you measure test coverage?
20. What is Test Driven Development (TDD) in React?
21. How do you test error boundaries?
22. How do you mock window and browser APIs?
23. How do you test lazy loaded components?
24. How do you handle flaky tests?
25. What are best practices for testing React apps?

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8. Server-Side Rendering (SSR) & Next.js

1. What is the difference between CSR and SSR?
2. What is Next.js and why use it?
3. How do you implement SSR in Next.js?
4. What are getStaticProps and getServerSideProps?
5. Explain Incremental Static Regeneration (ISR).
6. How do you handle API routes in Next.js?
7. What is static site generation?
8. How does hydration work in React SSR?
9. What is pre-rendering in Next.js?
10. How do you deploy a Next.js app?
11. What are the benefits of ISR?
12. How do you optimize SEO in SSR apps?
13. What is the difference between SSG and SSR?
14. How do you fetch data in Next.js?
15. What is dynamic routing in Next.js?
16. How do you implement authentication in Next.js SSR?
17. Explain getInitialProps and why it?s deprecated.
18. How do you use middleware in Next.js?
19. What is API caching in Next.js?
20. Explain environment variables in Next.js.
21. What is fallback in SSG pages?
22. How do you use ISR with revalidate?
23. How do you integrate GraphQL with SSR?
24. What is streaming SSR in React 18?
25. How does Next.js handle image optimization?

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9. Styling in React

1. What are the different ways to style React components?
2. Explain CSS modules in React.
3. What is the difference between inline styles and CSS files?
4. What are styled-components?
5. How do you use Emotion for styling in React?
6. Explain Tailwind CSS with React.
7. What are advantages of CSS-in-JS?
8. How do you apply conditional styles in React?
9. How do you manage global styles in React?
10. What is theming in styled-components?
11. How do you implement dark mode in React?
12. How do you use classnames library?
13. What is CSS scoping in React?
14. How do you implement animations in React?
15. Explain React Spring.
16. How do you integrate Framer Motion?
17. How do you implement responsive design in React?
18. What is utility-first CSS?
19. Explain BEM methodology in React projects.
20. How do you optimize CSS bundle size?
21. How do you load external stylesheets in React?
22. How do you apply styles conditionally with props?
23. What are global style resets?
24. How do you manage CSS variables in React?
25. What are best practices for styling large React apps?

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10. Advanced Concepts & Architecture

1. What are Higher-Order Components (HOC)?
2. What are Render Props?
3. Explain Compound Components pattern.
4. What is Context API and when to use it?
5. Explain Micro-Frontend architecture with React.
6. How do you structure a scalable React project?
7. What is React Concurrent Mode?
8. Explain Suspense for data fetching.
9. What is Server Components in React 18?
10. How do you implement Module Federation with React?
11. What are design systems in React apps?
12. Explain Clean Architecture in React projects.
13. What are monorepos in React development?
14. How do you use Nx for React monorepos?
15. Explain container-presenter pattern.
16. What are uncontrolled vs controlled patterns?
17. How do you implement pub-sub pattern in React?
18. What is dependency injection in React?
19. How do you handle feature toggles in React apps?
20. What are Edge Functions with React?
21. How do you use WebSockets in React?
22. What are Web Workers in React apps?
23. How do you handle multi-language apps in React?
24. Explain GraphQL integration with React.
25. How do you design enterprise-scale React applications?

#Angular

Last updated    - V4 (13-Sep-2025)

Level Topic Subtopics Basic Introduction What is Angular, Angular vs AngularJS, Features, Angular Architecture, Angular CLI Components Component Basics, Templates, Metadata, Lifecycle Hooks, Component Interaction Data Binding Interpolation, Property Binding, Event Binding, Two-way Binding, Template Reference Variables Directives Structural Directives (ngIf, ngFor), Attribute Directives, Built-in Directives, Custom Directives, ngSwitch Modules NgModule, Root Module, Feature Modules, Shared Modules, Lazy Loading Modules Intermediate Services & DI Creating Services, Dependency Injection, Hierarchical Injectors, providedIn, Service Scopes Forms Template-driven Forms, Reactive Forms, FormGroup & FormControl, Form Validation, Async Validators Routing RouterModule, RouterOutlet, Route Guards, Route Parameters, Child Routes Pipes Built-in Pipes, Async Pipe, Parameterized Pipes, Pure vs Impure Pipes, Custom Pipes Observables & RxJS Observable Basics, Operators (map, filter, switchMap), Subjects & BehaviorSubjects, Async/Await vs Observables, Error Handling Advanced Change Detection Zone.js, Change Detection Strategies, OnPush Strategy, DetectChanges(), Performance Tuning State Management NgRx, Akita, NGXS, Redux Pattern, Store & Effects HTTP Client HttpClientModule, Interceptors, Error Handling, Retry & Caching, REST API Integration Testing Unit Testing with Jasmine & Karma, TestBed, Mock Services, E2E Testing with Protractor, Cypress Performance Optimization Lazy Loading, Preloading Strategies, Ahead-of-Time Compilation (AOT), Tree Shaking, Bundle Optimization Expert Architecture & Patterns Monorepos with Nx, Micro-Frontends, Clean Architecture in Angular, Modular Federation, Smart vs Dumb Components Security XSS Protection, CSP, DomSanitizer, JWT Authentication, OAuth2 & OpenID Connect Internationalization i18n, Localization, Transloco, Angular Built-in i18n, Dynamic Language Switching Advanced RxJS Higher-order Observables, Multicasting, Custom Operators, Marble Testing, Backpressure Handling Deployment & CI/CD Angular Universal (SSR), Dockerizing Angular Apps, CI/CD Pipelines, Hosting (Firebase, AWS, Azure), SEO Optimization

1. Angular Core

1. What is Angular and how is it different from AngularJS?
2. What are Angular Modules and why are they important?
3. What are Angular decorators? Name a few.
4. Explain the role of NgModule in Angular.
5. What is a singleton pattern in Angular modules?
6. What is Ivy in Angular?
7. What is Angular CLI and its benefits?
8. What is Ahead-of-Time (AOT) compilation?
9. Explain Angular?s compilation process.
10. Difference between Angular compiler (ngc) and TypeScript compiler (tsc)?
11. How does Angular support TypeScript features?
12. What is tree-shaking in Angular?
13. Explain Angular zones and their purpose.
14. What is Angular Universal?
15. How does Angular handle internationalization (i18n)?
16. What is differential loading in Angular?
17. What are polyfills in Angular?
18. What are Angular schematics?
19. How does Angular handle DOM sanitization?
20. What is the purpose of Angular package.json configuration?

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2. Components

1. What is a component in Angular?
2. How do you create a component using Angular CLI?
3. What is a component selector?
4. Difference between inline and external templates?
5. What are component lifecycle hooks? Explain them.
6. How does ngOnInit differ from a constructor?
7. How do you pass data from parent to child component?
8. How do you emit events from child to parent?
9. What is ViewEncapsulation in Angular?
10. Difference between Shadow DOM and Emulated encapsulation?
11. How do you use @Input() and @Output() decorators?
12. What is Content Projection (ng-content)?
13. Difference between ViewChild and ContentChild?
14. What are dynamic components?
15. How do you reuse components across modules?
16. What are smart and dumb components?
17. How do you style Angular components?
18. How do you test a component in Angular?
19. What is OnPush change detection in components?
20. What are standalone components in Angular?

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3. Directives

1. What are Angular directives?
2. Difference between structural and attribute directives?
3. Examples of built-in directives in Angular?
4. What is *ngIf and how does it work?
5. What is *ngFor and how does trackBy improve performance?
6. What is ngSwitch directive?
7. How do you create a custom directive?
8. Difference between host binding and host listener?
9. What is ngClass and ngStyle directive?
10. What are async pipes and how are they used with directives?
11. Can you apply multiple directives to the same element?
12. Difference between ElementRef and Renderer2?
13. What is a structural directive marker (*)?
14. How do you conditionally apply classes using directives?
15. What are template reference variables in directives?
16. What is the purpose of Angular template syntax #var?
17. How do you manipulate DOM safely in directives?
18. How to share data between directives?
19. Difference between attribute binding and property binding?
20. Best practices when creating custom directives?

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4. Services & Dependency Injection

1. What is a service in Angular?
2. Why do we use services instead of duplicating logic in components?
3. What is Dependency Injection (DI)?
4. What is the difference between providedIn: root and module-level providers?
5. What is hierarchical dependency injection in Angular?
6. What happens if a service is provided at component level?
7. How do you create a singleton service?
8. How do you inject a service into another service?
9. Difference between useClass, useValue, useFactory providers?
10. What is a multi-provider in Angular?
11. How does Angular resolve dependencies at runtime?
12. What is the purpose of Injectable() decorator?
13. What is Optional() dependency in Angular?
14. What is Self() and SkipSelf() in Angular DI?
15. How does Angular handle circular dependency in DI?
16. What is the difference between root injector and module injector?
17. How do you configure environment-based services?
18. How do you mock a service in unit testing?
19. What is InjectionToken in Angular?
20. Explain the difference between service scope in lazy loaded vs eagerly loaded modules.

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5. Routing & Navigation

1. How is routing implemented in Angular?
2. What is RouterModule and how is it configured?
3. What are route parameters?
4. How do you implement query parameters in Angular routing?
5. What are route guards? Types of guards?
6. Difference between CanActivate and CanDeactivate?
7. What is CanLoad in routing?
8. What is lazy loading in Angular routing?
9. How to preload modules in routing?
10. What is RouterOutlet directive?
11. What is ActivatedRoute in Angular?
12. Difference between snapshot and observable in ActivatedRoute?
13. How do you handle route navigation programmatically?
14. How to implement child routes in Angular?
15. Difference between HashLocationStrategy and PathLocationStrategy?
16. What is the difference between forRoot and forChild in routing?
17. How do you create a custom route matcher?
18. How do you implement wildcard routes?
19. What is route resolver in Angular?
20. How do you pass state while navigating routes?

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6. Forms (Template-driven & Reactive)

1. Difference between template-driven and reactive forms?
2. What are form controls?
3. What is FormGroup in reactive forms?
4. How do you perform form validation in Angular?
5. How do you create custom validators?
6. What is async validation?
7. What is FormBuilder in Angular?
8. Difference between setValue() and patchValue()?
9. How do you disable form controls dynamically?
10. What is ngModel in Angular?
11. How do you bind form data to components?
12. How to reset a form programmatically?
13. What is touched vs dirty in Angular forms?
14. How do you handle cross-field validation?
15. How do you show validation error messages dynamically?
16. What is a dynamic form in Angular?
17. Difference between synchronous and asynchronous validators?
18. How do you test reactive forms?
19. What is updateOn in reactive forms?
20. What is the purpose of AbstractControl in Angular?

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7. RxJS & Observables

1. What is RxJS in Angular?
2. Difference between Observable and Promise?
3. What is a Subject in RxJS?
4. Difference between Subject, BehaviorSubject, ReplaySubject?
5. What is an Operator in RxJS? Examples?
6. What is pipe() in RxJS?
7. What is map, filter, and switchMap in RxJS?
8. Difference between mergeMap, concatMap, and exhaustMap?
9. What is debounceTime in RxJS?
10. How do you unsubscribe from Observables?
11. What are hot and cold Observables?
12. What is shareReplay in RxJS?
13. What is forkJoin operator?
14. What is combineLatest operator?
15. What is race operator in RxJS?
16. How to create a custom Observable?
17. What is takeUntil in RxJS?
18. How does Angular use RxJS internally?
19. Difference between async/await and Observables?
20. What is the purpose of firstValueFrom and lastValueFrom?

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8. Change Detection

1. What is Angular?s change detection?
2. What is the default change detection strategy?
3. Difference between default and OnPush strategy?
4. What is Zone.js in Angular?
5. How to manually trigger change detection?
6. What is ApplicationRef.tick() in Angular?
7. What is ChangeDetectorRef in Angular?
8. Difference between detectChanges() and markForCheck()?
9. How does Angular optimize change detection?
10. What is immutability and why does it help with OnPush?
11. What is ngDoCheck lifecycle hook?
12. How does Angular detect changes in arrays and objects?
13. Difference between pure and impure pipes in change detection?
14. What is the async pipe?s role in change detection?
15. How does trackBy improve *ngFor performance?
16. How does Angular handle change detection with observables?
17. What happens when Zone.js is removed from Angular?
18. Can you disable change detection temporarily?
19. How do you profile Angular change detection performance?
20. What is the difference between manual and automatic change detection?

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9. Testing

1. How do you unit test components in Angular?
2. What is TestBed in Angular?
3. What is Jasmine in Angular testing?
4. What is Karma test runner?
5. How do you mock services in Angular unit tests?
6. What is a spy in Jasmine?
7. How do you test HTTP requests in Angular?
8. What is HttpTestingController?
9. Difference between unit tests and integration tests?
10. What is Protractor in Angular?
11. What is Cypress and can it be used with Angular?
12. What are async and fakeAsync utilities in Angular testing?
13. How do you test form validation in Angular?
14. How do you test route guards in Angular?
15. How to test directives in Angular?
16. How do you test pipes in Angular?
17. What is Angular testing module?
18. How do you test event emitters?
19. Difference between shallow testing and deep testing?
20. Best practices for Angular unit testing?

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10. Performance & Best Practices

1. How do you improve performance in Angular apps?
2. What is Ahead-of-Time (AOT) compilation?
3. What is Tree-shaking in Angular?
4. How to optimize change detection for large applications?
5. Best practices for structuring Angular applications?
6. How does lazy loading improve performance?
7. How do you reduce bundle size in Angular?
8. What is Angular CLI build optimizer?
9. What are service workers in Angular?
10. How to implement server-side rendering (SSR)?
11. What is differential loading and its benefits?
12. How to handle memory leaks in Angular apps?
13. What are best practices for RxJS usage?
14. How to implement caching in Angular?
15. Difference between ngZone run() and runOutsideAngular()?
16. How to optimize *ngFor performance?
17. What are Angular PWA best practices?
18. How to secure Angular applications?
19. What are Angular best practices for folder structure?
20. How to improve initial load time in Angular apps?