1What is HTML?
HTML (HyperText Markup Language) structures web content and elements on a webpage.
2What is the DOM?
The Document Object Model (DOM) is a programming interface for HTML and XML documents, representing the page so programs can change structure, style, and content.
3What is CSS?
CSS (Cascading Style Sheets) describes the presentation of a document written in HTML or XML.
4Explain the box model in CSS.
It includes content, padding, border, and margin, defining the total space an element occupies.
5What is Flexbox?
Flexbox is a CSS layout model that allows items to align and distribute space within a container efficiently.
6What are CSS preprocessors?
CSS preprocessors like Sass and Less extend CSS with variables, nesting, and functions.
7What is JavaScript?
JavaScript is a programming language for creating dynamic web content, such as interactive forms and animations.
8Explain event delegation.
Attaching one event listener to a parent element to handle events for multiple children using bubbling.
9What is AJAX?
AJAX (Asynchronous JavaScript and XML) lets pages update asynchronously by exchanging data with a server.
10What is React?
React is a JS library for building UIs with component-based architecture and state management.
11What is JSX?
JSX is a syntax extension for JavaScript, used in React to describe UI elements.
12Explain virtual DOM.
A lightweight copy of the real DOM, used by React for efficient updates and rendering.
13What are hooks in React?
Hooks are functions that let functional components use state and lifecycle features.
14What is Redux?
Redux is a state management library for JavaScript applications, centralizing app state.
15Difference between props and state in React?
Props are read-only and passed from parent to child, while state is mutable data within a component.
16What is Angular?
Angular is a framework for building single-page client apps with HTML and TypeScript.
17What are directives in Angular?
Special markers in the DOM that extend HTML with new behavior.
18Explain data binding in Angular.
Synchronizes data between model and view, supporting one-way and two-way binding.
19What is Vue.js?
Vue.js is a progressive JS framework for building UIs and SPAs.
20What is the Vue instance?
The root of a Vue app, controlling its lifecycle.
21What are single-file components in Vue.js?
They encapsulate HTML, CSS, and JS in a single .vue file.
22Explain lifecycle hooks in Vue.js.
Methods that run at specific stages like created, mounted, destroyed.
23What is TypeScript?
A superset of JS adding static types to improve code quality.
24Benefits of using TypeScript?
Better readability, early error detection, tooling support.
25What is Webpack?
A module bundler for JS applications, transforming and packaging code.
26Explain lazy loading.
Delays loading of non-critical resources until needed.
27What are service workers?
Scripts running in background for offline use and syncing.
28What is PWA?
Progressive Web Apps bring app-like experiences, offline access, push notifications.
29What is responsive design?
Adapts web content to different devices and screen sizes.
30What is a media query?
CSS technique to apply styles based on device characteristics like width.
31What is a CSS grid?
A 2D layout system for creating complex web layouts.
32Difference between == and === in JS?
== checks equality with type coercion, === checks without coercion.
33What is a closure in JS?
A function that retains access to its lexical scope.
34What is 'this' keyword in JS?
Refers to the context of function execution.
35What is the event loop in JS?
Mechanism handling async operations by executing callbacks.
36Explain async/await.
Syntax for working with promises in a synchronous style.
37What is CORS?
A security feature allowing or restricting resource access across domains.
38What is REST API?
An architectural style using HTTP requests for CRUD operations.
39What is GraphQL?
A query language for APIs enabling clients to fetch specific data.
40Difference between localStorage & sessionStorage?
localStorage persists indefinitely; sessionStorage lasts for the session only.
41What is JSON?
JSON is a lightweight data format, easy for humans to read and machines to parse.
42What is an IIFE in JS?
Immediately Invoked Function Expression runs right after definition.
43What is the Shadow DOM?
Encapsulates part of the DOM tree for scoped styling and behavior.
44What is a CSS transition?
Allows control over speed of CSS property changes (animations).
45What is a polyfill?
Code that provides modern functionality on older browsers.
46What is BEM in CSS?
Block Element Modifier naming convention for scalable, maintainable CSS.
47What is a CSS variable?
Custom properties defined by authors to reuse values across stylesheets.
48What is a higher-order component (HOC) in React?
A function that takes a component and returns a new one with added functionality.
49What is memoization?
Optimization technique caching function results for performance.
50Difference between let and const in JS?
let allows reassignment, const declares immutable references.