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Web Technologies Questions

Page 3 of 13 (Displaying Questions 201 – 300 of 1207 Total)

201. What is the purpose of the `will-change` CSS property?

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It is used as an optimization hint to the browser, informing it in advance which properties on an element are expected to change, allowing it to prepare necessary optimizations.

Added: Nov 30, 2025

202. How do you style elements based on their parent's state in CSS?

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Using the `:has()` relational pseudo-class, which allows selection of an element if any of the relative selectors passed as arguments match.

Added: Nov 30, 2025

203. What is the difference between `filter` and `backdrop-filter`?

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`filter` applies visual effects (blur, grayscale) to the element itself. `backdrop-filter` applies effects to the area behind the element.

Added: Nov 30, 2025

204. What is `initial` layout in CSS?

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The initial or default positioning and sizing of elements as determined by the browser before any custom CSS or user agent styles are applied.

Added: Nov 30, 2025

205. How do you ensure form accessibility beyond just required fields?

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By using proper labeling (`<label for="id">`), keyboard navigation checks (tabindex), and ARIA attributes for custom controls.

Added: Nov 30, 2025

206. What is the Observer pattern in JavaScript?

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A design pattern where an object (Subject) maintains a list of dependents (Observers) and notifies them automatically of any state changes.

Added: Nov 30, 2025

207. Explain the Factory pattern.

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A creational pattern that uses a factory method to create objects without specifying the exact class or constructor, abstracting the instantiation logic.

Added: Nov 30, 2025

208. What is the Singleton pattern?

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A design pattern that restricts the instantiation of a class to one object (or single instance).

Added: Nov 30, 2025

209. What is the Mediator pattern?

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A behavioral pattern that allows objects to communicate indirectly through a central mediator object, reducing direct dependencies.

Added: Nov 30, 2025

210. Explain the differences between MVC, MVP, and MVVM architectural patterns.

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MVC separates logic into Model, View, Controller. MVP uses a Presenter to intermediate between Model and View. MVVM uses a ViewModel with data binding to connect View and Model.

Added: Nov 30, 2025

211. What is the Proxy pattern in web development?

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It provides a surrogate or placeholder for another object to control access to it, often used for lazy instantiation or validation.

Added: Nov 30, 2025

212. What are Custom Elements in Web Components?

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User-defined HTML elements with custom functionality and encapsulated styles, defined using the CustomElementRegistry API.

Added: Nov 30, 2025

213. What is the use of the `adoptedStyleSheets` API?

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It allows CSS style sheets to be shared and reused across multiple Shadow Roots or the document, improving performance and reducing style duplication.

Added: Nov 30, 2025

214. What is the Intersection Observer API?

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A modern API that provides a way to asynchronously observe changes in the intersection of a target element with an ancestor element or with the document's viewport.

Added: Nov 30, 2025

215. What is the Resize Observer API?

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An API that provides a performant mechanism for monitoring when an element's size changes, without relying on continuous polling or window resize events.

Added: Nov 30, 2025

216. Explain the concept of Push API and Notifications API.

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Push API allows a Service Worker to receive messages from a server even when the app is not actively running. Notifications API displays those messages to the user.

Added: Nov 30, 2025

217. What is the Web Storage API?

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The collective name for localStorage and sessionStorage, providing mechanisms for storing simple key-value pairs client-side.

Added: Nov 30, 2025

218. What is the Page Visibility API?

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An API that lets you know when a page is visible to the user, allowing optimized resource usage by pausing non-critical operations when the page is hidden.

Added: Nov 30, 2025

219. What is the difference between a synchronous and an asynchronous script?

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Synchronous scripts halt HTML parsing until they are fetched and executed. Asynchronous scripts (using `async` or `defer`) do not halt parsing.

Added: Nov 30, 2025

220. What is the Web Cryptography API?

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An API that provides cryptographic primitives to perform basic operations like hashing, signing, and encryption directly in the browser.

Added: Nov 30, 2025

221. Explain the purpose of the Permissions API.

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It allows developers to query the status of different browser permissions (like geolocation or notifications) without having to trigger a permission request.

Added: Nov 30, 2025

222. What is the Web Speech API?

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A collection of APIs that enable the browser to interpret speech (Speech Recognition) and synthesize speech (Speech Synthesis).

Added: Nov 30, 2025

223. How do you prevent a form from submitting while an asynchronous operation is running?

Show Answer

By disabling the submit button and/or using `event.preventDefault()` in the submit handler until the operation is complete.

Added: Nov 30, 2025

224. What are regular expressions in JavaScript?

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Patterns used to match character combinations in strings, often used for validation or search-and-replace operations.

Added: Nov 30, 2025

225. What is the benefit of using `requestIdleCallback`?

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It schedules a function to be run when the browser is idle, ensuring that non-essential, background tasks don't interfere with critical animations or user input.

Added: Nov 30, 2025

226. What is Content Security Policy (CSP)?

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An HTTP response header that defines which dynamic resources are allowed to load, mitigating XSS and data injection attacks.

Added: Nov 30, 2025

227. What is the X-Content-Type-Options header used for?

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It prevents browsers from "sniffing" a response away from the declared content-type, helping to mitigate content confusion attacks.

Added: Nov 30, 2025

228. Explain the X-Frame-Options header.

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A security header used to prevent clickjacking attacks by dictating whether a browser should be allowed to render a page in a <frame>, <iframe>, or <object>.

Added: Nov 30, 2025

229. What is Public Key Pinning (HPKP)?

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A security measure (now largely deprecated) that told browsers to remember, or "pin," the SSL certificate for a website to prevent MITM attacks using fraudulent certificates.

Added: Nov 30, 2025

230. How do refresh tokens differ from access tokens in OAuth?

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Access tokens grant access to protected resources and are short-lived. Refresh tokens are long-lived and used to obtain a new access token once the current one expires.

Added: Nov 30, 2025

231. What is Certificate Transparency (CT)?

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A protocol that provides a public, verifiable record of all SSL/TLS certificates issued by Certificate Authorities, helping to catch misissued or malicious certificates.

Added: Nov 30, 2025

232. What is the purpose of the `no-referrer` header policy?

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It prevents the browser from sending any referrer information when navigating away from the current document, enhancing user privacy.

Added: Nov 30, 2025

233. Explain SQL Injection and how to prevent it.

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A security flaw where an attacker can interfere with the queries that an application makes to its database. Prevented primarily by using parameterized queries (prepared statements).

Added: Nov 30, 2025

234. What is a security vulnerability disclosure policy?

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A set of guidelines outlining how security researchers can responsibly report vulnerabilities they discover in a system to the organization.

Added: Nov 30, 2025

235. What is the role of a Web Application Firewall (WAF)?

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A firewall that monitors, filters, or blocks HTTP traffic to and from a web application, protecting it from attacks like XSS, SQLi, and CSRF.

Added: Nov 30, 2025

236. What are Progressive Web Apps (PWAs)?

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Web applications built using modern web capabilities to deliver an app-like user experience, featuring offline support, installability, and fast loading.

Added: Nov 30, 2025

237. What is the Web App Manifest?

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A JSON file that provides information about a PWA (name, icons, start URL) to the browser, necessary for the app to be "installed" on the user's device.

Added: Nov 30, 2025

238. Explain the concept of offline-first.

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A development philosophy that prioritizes the user experience when the device is offline or has a poor network connection, often using Service Workers and caching.

Added: Nov 30, 2025

239. What is the difference between a Single Page Application (SPA) and a Multi-Page Application (MPA)?

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SPA loads a single HTML page and dynamically updates content. MPA requires the browser to load a new HTML page for every navigation.

Added: Nov 30, 2025

240. What is hydration in client-side rendering frameworks?

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The process where client-side JavaScript attaches event listeners and state to the server-rendered HTML markup, making the page interactive.

Added: Nov 30, 2025

241. What is Jamstack?

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A modern web architecture based on client-side JavaScript, reusable APIs, and prebuilt Markup, emphasizing speed, security, and scalability.

Added: Nov 30, 2025

242. Explain the purpose of Static Site Generators (SSGs).

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Tools (like Jekyll or Hugo) that build a complete, static HTML website from source files (markdown, templates) at deployment time, avoiding server-side processing at runtime.

Added: Nov 30, 2025

243. What is the difference between client-side and server-side routing?

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Client-side routing changes the visible URL and updates the DOM without a full page reload. Server-side routing requires the server to send a new HTML document for every URL change.

Added: Nov 30, 2025

244. What is the Virtual DOM (VDOM)?

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A programming concept where a virtual representation of the UI is kept in memory and synced with the "real" DOM. It is used to minimize direct DOM manipulations for better performance.

Added: Nov 30, 2025

245. Explain the concept of WebAssembly (Wasm).

Show Answer

A low-level binary instruction format for a stack-based virtual machine, designed as a portable compilation target for high-level languages like C/C++/Rust, allowing near-native performance on the web.

Added: Nov 30, 2025

246. What is the event phase of an event listener?

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It refers to the three stages of event propagation: capturing phase (down the tree), target phase (at the element), and bubbling phase (up the tree).

Added: Nov 30, 2025

247. What is debouncing?

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A technique to limit the rate at which a function fires. It ensures a function is executed only after a specified period of inactivity.

Added: Nov 30, 2025

248. What is throttling?

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A technique to limit the rate at which a function fires. It ensures a function executes at most once every specified period.

Added: Nov 30, 2025

249. What are JavaScript Proxies used for?

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To create an object that can be used in place of another object, enabling custom behavior like validation, access logging, or handling non-existent properties.

Added: Nov 30, 2025

250. Explain the concept of a Microfrontend architecture.

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An architectural style where a large frontend application is broken down into smaller, independent, and deployable units, each managed by a different team.

Added: Nov 30, 2025

251. What is the purpose of the `navigator` object?

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It contains information about the browser, such as the user-agent, operating system, and support for various features.

Added: Nov 30, 2025

252. What is the global `window` object?

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The object representing the window in which the script is running. It is the topmost object in the DOM hierarchy and holds global variables and functions.

Added: Nov 30, 2025

253. How do you perform deep cloning in JavaScript?

Show Answer

The most common method is using `JSON.parse(JSON.stringify(object))`, though this method fails to copy functions, Dates, or Symbols.

Added: Nov 30, 2025

254. What is the purpose of the `finally` block in a try-catch statement?

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The code inside the `finally` block always executes, regardless of whether an exception was thrown or caught.

Added: Nov 30, 2025

255. What are default parameters in functions?

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A feature allowing named parameters to be initialized with default values if no value or `undefined` is passed.

Added: Nov 30, 2025

256. What is the `new.target` property?

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It is a meta-property available inside functions and constructors that tells you whether the function was called with the `new` keyword.

Added: Nov 30, 2025

257. Explain the term "polyfill".

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A piece of code (usually JavaScript) that provides the functionality of a newer API to older browsers that do not natively support it.

Added: Nov 30, 2025

258. What is functional programming (FP) in JavaScript?

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A programming paradigm that treats computation as the evaluation of mathematical functions and avoids changing state and mutable data.

Added: Nov 30, 2025

259. What is the role of `pure functions` in FP?

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A pure function always returns the same result given the same arguments and has no side effects (does not modify outside state).

Added: Nov 30, 2025

260. How do you handle multiple nested callbacks in legacy JavaScript?

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Using techniques like promises, async/await, or modularizing the code to avoid deeply indented "callback hell."

Added: Nov 30, 2025

261. What is a closure property of an arrow function?

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Arrow functions do not have their own `this` context. Instead, they lexically bind `this` to the context where they are defined (their parent scope).

Added: Nov 30, 2025

262. What is the difference between `let` and `const` regarding mutation?

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`const` prevents reassignment of the variable reference, but the value it points to (if an object or array) can still be mutated.

Added: Nov 30, 2025

263. How does the `for...of` loop differ from `for...in`?

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`for...of` iterates over iterable values (like array elements). `for...in` iterates over enumerable property names (keys) of an object.

Added: Nov 30, 2025

264. What is the purpose of the `WeakMap`?

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It is similar to a `Map` but its keys must be objects, and those keys are held weakly, allowing them to be garbage collected if no other references exist.

Added: Nov 30, 2025

265. Explain JavaScript `Tagged Templates`.

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A more advanced form of template literals where the template is preceded by a function call (the tag). The function receives the string parts and variable values.

Added: Nov 30, 2025

266. What is a mutation observer?

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An API that provides a way to detect changes to the DOM tree (additions, removals, attribute changes).

Added: Nov 30, 2025

267. How do you manually dispatch an event in JavaScript?

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Using the `dispatchEvent` method on an element after creating a new event object (e.g., `new CustomEvent`).

Added: Nov 30, 2025

268. What is the difference between a custom element and a custom data attribute?

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A custom element is a new HTML tag with encapsulated behavior. A custom data attribute (`data-*`) is an attribute on an existing element to store data.

Added: Nov 30, 2025

269. What is the role of the `sandbox` attribute on an `<iframe>`?

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It applies restrictions to the content within the frame, such as disabling scripts, forms, or navigating the top-level window, enhancing security.

Added: Nov 30, 2025

270. Explain the purpose of the `referrerpolicy` attribute.

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It controls how much referrer information (URL of the requesting page) should be included with HTTP requests.

Added: Nov 30, 2025

271. What is the use of `prefers-color-scheme` media query?

Show Answer

It allows developers to serve different styles based on whether the user has set their operating system to light or dark mode.

Added: Nov 30, 2025

272. How do you create a "sticky" header that is visually distinct when scrolled?

Show Answer

Use `position: sticky;` combined with JavaScript/Intersection Observer to add a class to the header when the scroll position meets a threshold.

Added: Nov 30, 2025

273. What are CSS Flex Shorthands?

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Shorthand properties like `flex-flow` (combining `flex-direction` and `flex-wrap`) and the `flex` property (combining `flex-grow`, `flex-shrink`, and `flex-basis`).

Added: Nov 30, 2025

274. Explain the difference between `repeat()` and `auto-fill`/`auto-fit` in CSS Grid.

Show Answer

`repeat()` defines a fixed number of tracks. `auto-fill`/`auto-fit` dynamically adjusts the number of tracks based on the container size and track minimum size.

Added: Nov 30, 2025

275. What are viewport units (vmin, vmax)?

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Units relative to the viewport size: `vmin` is the minimum of `vw` or `vh`. `vmax` is the maximum of `vw` or `vh`.

Added: Nov 30, 2025

276. How do you create fluid typography using `clamp()`?

Show Answer

`clamp(min, preferred, max)` allows you to set a minimum font size, a preferred responsive size (e.g., `3vw`), and a maximum font size, preventing text from becoming too small or too large.

Added: Nov 30, 2025

277. What is the difference between `background-size: cover` and `contain`?

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`cover` scales the image to cover the entire background area, potentially cropping. `contain` scales the image to fit entirely within the background area, showing the whole image.

Added: Nov 30, 2025

278. What is the purpose of the `accent-color` property?

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A CSS property used to set the color tint for form elements (checkboxes, radio buttons, range inputs) with a single property.

Added: Nov 30, 2025

279. How does the `filter` property affect performance?

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Some filter values (like `blur` or `drop-shadow`) can be computationally expensive, particularly if applied to large areas or changing often, potentially forcing GPU usage.

Added: Nov 30, 2025

280. What are CSS variables (custom properties) useful for?

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Reducing repetition, making code easier to maintain, and enabling runtime manipulation of styles via JavaScript.

Added: Nov 30, 2025

281. What is the difference between a CSS transform and a transition?

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A transform is a set of geometric operations (translate, scale, rotate) applied instantaneously. A transition smoothly animates the change in a property over time.

Added: Nov 30, 2025

282. What is the purpose of the `box-decoration-break` property?

Show Answer

It specifies how an element's box model properties (padding, border, margin) should be rendered when the box is fragmented (e.g., when text wraps across multiple lines).

Added: Nov 30, 2025

283. What is the `backdrop-filter` property used for?

Show Answer

It applies graphical effects like blur or color shifts to the area *behind* an element, allowing the background to show through the filter effect.

Added: Nov 30, 2025

284. What is a CSS hook?

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A specific, non-semantic class name or custom property used solely as a target for JavaScript or a preprocessor.

Added: Nov 30, 2025

285. How do you implement infinite scrolling (lazy loading on scroll)?

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By attaching an event listener to the window/container scroll event, or more efficiently, using the Intersection Observer API to detect when the last item enters the viewport.

Added: Nov 30, 2025

286. What is a Race Condition in JavaScript?

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A situation where two or more asynchronous tasks access a shared resource and the outcome depends on the unpredictable order of their execution.

Added: Nov 30, 2025

287. Explain the purpose of the `finally` block in Promise chains.

Show Answer

It is used for cleanup operations that must be executed regardless of whether the Promise was fulfilled or rejected.

Added: Nov 30, 2025

288. What is the role of `Object.freeze()`?

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It prevents new properties from being added to an object, prevents existing properties from being removed, and prevents the values or writability of existing properties from being changed.

Added: Nov 30, 2025

289. What are Array Buffers and Typed Arrays?

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Array Buffers are raw binary data buffers. Typed Arrays provide views (like Int8Array, Float64Array) into these buffers for handling specific numeric types.

Added: Nov 30, 2025

290. What is the `structuredClone()` function?

Show Answer

A modern built-in JavaScript function used to perform a deep copy of a value, capable of cloning complex objects, Maps, Sets, and Typed Arrays.

Added: Nov 30, 2025

291. What is module bundling?

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The process of taking various source files (JavaScript, CSS, assets) and compiling them into a small number of optimized files suitable for deployment.

Added: Nov 30, 2025

292. How does a Webpack loader differ from a Webpack plugin?

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Loaders process source files (e.g., transform ES6 to ES5). Plugins execute during the entire compilation lifecycle to modify how the bundle is created (e.g., optimization).

Added: Nov 30, 2025

293. What is hot module replacement (HMR)?

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A feature of modern bundlers that allows JavaScript modules to be updated in a running application without a full page reload, preserving the application state.

Added: Nov 30, 2025

294. Explain the concept of Serverless Architecture.

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A model where the cloud provider manages the server infrastructure, automatically scaling resources, and developers pay only for the compute time consumed.

Added: Nov 30, 2025

295. What is the purpose of a reverse proxy?

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A server that sits in front of one or more web servers, intercepting client requests, and directing them to the appropriate backend server (e.g., Nginx).

Added: Nov 30, 2025

296. What is the difference between latency and throughput?

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Latency is the time delay before a transfer of data begins following an instruction. Throughput is the rate at which data is successfully transferred per unit of time.

Added: Nov 30, 2025

297. How is data typically exchanged in microservices architecture?

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Through synchronous requests (like REST/gRPC) or asynchronous messages (via message queues/brokers).

Added: Nov 30, 2025

298. What is the purpose of the `same-origin` policy in iframes?

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It prevents scripts in the iframe from accessing or manipulating the content of the parent window if they are loaded from different origins.

Added: Nov 30, 2025

299. What is a Session Hijacking attack?

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An attack where an attacker steals a valid session ID to gain unauthorized access to a user's account, often through XSS or MITM.

Added: Nov 30, 2025

300. What is input validation in security?

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The process of ensuring that user-provided data matches the expected format, type, and length before it is processed or stored, preventing injection attacks.

Added: Nov 30, 2025

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