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Web Technologies Questions

Page 11 of 13 (Displaying Questions 1001 – 1100 of 1207 Total)

1001. What is the JavaScript `ShadowRealm` API proposal?

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A proposed API for creating a secure, isolated environment within a JavaScript realm, allowing code execution without sharing global objects with the parent realm.

Added: Nov 30, 2025

1002. Explain the concept of `Microtasks` vs. `Macrotasks`.

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Microtasks (like Promises) execute immediately after the currently running task. Macrotasks (like `setTimeout`) execute in subsequent iterations of the event loop, after all microtasks have run.

Added: Nov 30, 2025

1003. What is the `requestIdleCallback` API?

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A browser API that schedules a function to be run during the browser's idle periods, helping to perform non-essential, low-priority work without blocking the main thread.

Added: Nov 30, 2025

1004. What is the `scheduler.postTask` API?

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A proposed modern API for scheduling tasks with different priorities (`user-blocking`, `user-visible`, `background`), giving the developer more control over the main thread.

Added: Nov 30, 2025

1005. What is the purpose of the `worker-src` directive in CSP?

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A directive that controls which sources are valid for loading Worker scripts, Shared Worker scripts, or Service Worker scripts.

Added: Nov 30, 2025

1006. What are `Shared Workers`?

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Workers that can be accessed by multiple scripts running in different windows, tabs, or iframes of the same origin, allowing for centralized state management across tabs.

Added: Nov 30, 2025

1007. How do `Web Workers` and the `main thread` communicate?

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Via the `postMessage()` method, which sends a copy of the data (not a reference) between the worker and the main thread.

Added: Nov 30, 2025

1008. What is a `Transferable Object` in Web Workers?

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An object (like `ArrayBuffer` or `MessagePort`) that can be transferred from the main thread to a worker (or vice versa) without copying, dramatically improving performance for large data sets.

Added: Nov 30, 2025

1009. What is the JavaScript `top-level await` feature?

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The ability to use the `await` keyword at the top level of an ES Module, allowing module fetching and initialization logic to pause until an asynchronous operation completes.

Added: Nov 30, 2025

1010. What is the JavaScript `class field` proposal?

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A feature that simplifies class syntax by allowing properties to be defined directly as fields inside the class body, including support for `#private` fields.

Added: Nov 30, 2025

1011. What is the `Intl.DisplayNames` object?

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An object in the Internationalization API that enables the localized display of language, region, and script names.

Added: Nov 30, 2025

1012. What is the purpose of `Intl.PluralRules`?

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An Internationalization object that determines the correct plural form of a word based on a given number and locale, crucial for supporting multiple languages correctly.

Added: Nov 30, 2025

1013. What is `WebMIDI API`?

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An API that allows web pages to communicate with MIDI (Musical Instrument Digital Interface) devices connected to the user's computer, enabling musical applications.

Added: Nov 30, 2025

1014. What is the `WebUSB API`?

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An API that exposes connected USB devices to web pages, allowing web applications to communicate with devices, provided the user grants permission.

Added: Nov 30, 2025

1015. What is the `Bluetooth Low Energy (BLE)` protocol?

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A wireless personal area network technology designed for significantly lower power consumption than standard Bluetooth, often used for IoT and wearable devices.

Added: Nov 30, 2025

1016. What is the purpose of the `WebAuthn` API?

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A web standard that allows users to authenticate to websites using public-key cryptography via hardware tokens (e.g., YubiKey) or platform authenticators (e.g., Face ID), enabling strong, phishing-resistant security.

Added: Nov 30, 2025

1017. What is a `Passkey`?

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A modern replacement for passwords that uses public-key cryptography (WebAuthn) for authentication, eliminating the need for a user to remember a complex password.

Added: Nov 30, 2025

1018. What is the `Subgrid` feature in CSS Grid?

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A value for `grid-template-columns` or `grid-template-rows` that allows a nested grid to inherit the track definition (columns/rows) of its parent grid.

Added: Nov 30, 2025

1019. What is the CSS `initial-letter` property?

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A property used to set the size and sinking of the first letter of a text block, allowing for magazine-style drop caps.

Added: Nov 30, 2025

1020. What is the `::marker` pseudo-element?

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A pseudo-element that allows styling of the marker box of a list item (e.g., the bullet point or number).

Added: Nov 30, 2025

1021. What is `CSS Custom Media Queries`?

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A proposed feature that allows developers to define custom aliases for media query expressions (e.g., `@custom-media --tablet (min-width: 768px)`).

Added: Nov 30, 2025

1022. Explain the `font-variant-numeric` property.

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A CSS property used to control the usage of font features that relate to numbers, such as displaying fractions, old-style numerals, or tabular figures.

Added: Nov 30, 2025

1023. What is the `prefers-reduced-motion` media query?

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A media feature that detects if the user has requested that the system minimize the amount of non-essential motion or animation.

Added: Nov 30, 2025

1024. What is the `prefers-color-scheme` media query?

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A media feature that detects if the user has requested the system to use a light or dark color theme.

Added: Nov 30, 2025

1025. What is the CSS property `contain: content`?

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A property value that hints to the browser that an element's layout, style, and paint can be fully contained, allowing the browser to skip rendering work outside of the element, improving performance.

Added: Nov 30, 2025

1026. What is `Total Blocking Time (TBT)`?

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A performance metric that measures the total time between FCP and TTI where the main thread was blocked long enough to prevent input responsiveness (tasks > 50ms).

Added: Nov 30, 2025

1027. What is `First Contentful Paint (FCP)`?

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A performance metric that measures the time from when the page starts loading to when any part of the page's content is rendered on the screen.

Added: Nov 30, 2025

1028. What is `Time to Interactive (TTI)`?

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A performance metric that measures the time until the layout has stabilized, key web fonts are visible, and the main thread is idle enough to handle user input reliably.

Added: Nov 30, 2025

1029. What is `RAIL` performance model?

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A user-centric performance model focusing on four aspects: **R**esponse (100ms), **A**nimation (16ms/frame), **I**dle (utilize idle time), and **L**oad (fast load time).

Added: Nov 30, 2025

1030. What is `Field Data` in web performance?

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Performance data collected from real users (RUM - Real User Monitoring) in the wild, typically represented by the Chrome User Experience Report (CrUX).

Added: Nov 30, 2025

1031. What is `Lab Data` in web performance?

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Performance data collected in a controlled environment using tools like Lighthouse or WebPageTest, useful for debugging and reproducible testing.

Added: Nov 30, 2025

1032. What is the `document.write()` method and its negative impact on performance?

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A synchronous method that writes a string of text or HTML to a document stream. If called after the document has loaded, it can force a full document reload and block rendering.

Added: Nov 30, 2025

1033. What is `CSS Selectors Level 4`?

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The current and future specification for CSS selectors, introducing advanced features like the `:has()` relational pseudo-class (parent selector) and scoping selectors.

Added: Nov 30, 2025

1034. What is the CSS `:has()` pseudo-class?

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A powerful relational selector that selects an element if any of the relative selectors passed into it match (e.g., `section:has(h1)` selects a section containing an H1).

Added: Nov 30, 2025

1035. What is `Cascade Layers` in CSS?

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A modern CSS feature (`@layer`) that provides developers with a structured way to manage the cascade, ensuring that styles within one layer take precedence over others, regardless of specificity.

Added: Nov 30, 2025

1036. How do you define a Cascade Layer in CSS?

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Using the `@layer layer-name { ... styles ... }` rule or the `@import url(...) layer(layer-name);` syntax.

Added: Nov 30, 2025

1037. What is the purpose of the `font-display: optional` descriptor?

Show Answer

A value used within `@font-face` that tells the browser to use a fallback font immediately if the custom font is not already in the cache, preventing a layout shift (FOIT/FOUT).

Added: Nov 30, 2025

1038. What is `FOIT (Flash of Invisible Text)`?

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A rendering issue where the browser waits for a custom web font to load, leaving the text invisible during the wait time.

Added: Nov 30, 2025

1039. What is `FOUT (Flash of Unstyled Text)`?

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A rendering issue where the browser first displays text using a fallback font, and then switches to the custom web font once it has loaded.

Added: Nov 30, 2025

1040. What is the `Performance Timeline`?

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A browser feature that provides a chronological, millisecond-accurate record of all performance events (loading, scripting, rendering) that occur during the page lifecycle.

Added: Nov 30, 2025

1041. What is `Resource Timing API`?

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A performance API that provides detailed network timing metrics for resources loaded by the document (CSS, images, scripts), including DNS lookup, connect, and fetch times.

Added: Nov 30, 2025

1042. What is `Long Animation Frame (LoAF)`?

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A proposed metric to replace FID, focusing on long animation frames to better measure the responsiveness of the main thread and jank in UI rendering.

Added: Nov 30, 2025

1043. What is `DNS Pre-fetch`?

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A resource hint (`<link rel="dns-prefetch" href="//example.com">`) that tells the browser to perform a DNS lookup on a domain in the background, minimizing latency when the resource is requested later.

Added: Nov 30, 2025

1044. What is `Preconnect`?

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A resource hint (`<link rel="preconnect" href="//example.com">`) that tells the browser to set up early connections (DNS lookup, TCP handshake, TLS negotiation) to a third-party domain.

Added: Nov 30, 2025

1045. What is `Reverse Proxy`?

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A server that sits in front of one or more web servers, forwarding client requests to the appropriate backend server, often used for load balancing, security, and SSL termination.

Added: Nov 30, 2025

1046. What is the `CORS Preflight Request`?

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An automatic `OPTIONS` HTTP request sent by the browser before the actual cross-origin request, asking the server's permission to execute the request with non-simple methods (PUT, DELETE) or custom headers.

Added: Nov 30, 2025

1047. What is the `Cross-Origin Resource Policy (CORP)` header?

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An HTTP header that allows a resource owner to explicitly control whether the resource can be loaded by a cross-origin context, even when the request is simple (mitigating side-channel attacks).

Added: Nov 30, 2025

1048. What is the security risk of using `target="_blank"` without `rel="noopener"`?

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It exposes the originating page to a reverse tabnabbing attack by giving the newly opened page access to the original page's window object via `window.opener`.

Added: Nov 30, 2025

1049. What is `TLS SNI (Server Name Indication)`?

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An extension to the TLS protocol that allows a client to specify the hostname it is trying to connect to at the start of the handshake, enabling a server to host multiple SSL certificates on a single IP address.

Added: Nov 30, 2025

1050. What is a `Certificate Transparency (CT) Log`?

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Publicly auditable, append-only records of all issued SSL/TLS certificates, designed to allow domain owners to detect mistakenly or maliciously issued certificates for their domain.

Added: Nov 30, 2025

1051. What is `Oblivious HTTP (OHTTP)`?

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An emerging privacy-enhancing technology that separates the client's IP address from the content of their HTTP request by routing it through an intermediary Oblivious Proxy.

Added: Nov 30, 2025

1052. What is the `iframe sandbox` attribute?

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An attribute used on an `<iframe>` that imposes restrictions on the content within the frame, such as disallowing scripts, form submissions, or top-level navigation, enhancing security.

Added: Nov 30, 2025

1053. What is the `Custom Elements` standard?

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A Web Components standard that allows developers to define new types of HTML elements with custom behavior and tags (e.g., `<my-button>`).

Added: Nov 30, 2025

1054. Explain the purpose of `Shadow DOM`.

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A mechanism for attaching an encapsulated, separate DOM tree to an element, isolating its structure, style, and behavior from the rest of the document.

Added: Nov 30, 2025

1055. What is `Declarative Shadow DOM`?

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A feature that allows Shadow DOM to be rendered on the server (SSR) by including a `<template shadowroot>` tag inside the host element, allowing for faster loading and better SEO.

Added: Nov 30, 2025

1056. What is the `Web Codecs API`?

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An API that provides low-level access to the video and audio codecs built into the browser, enabling efficient processing and manipulation of raw media streams in Web Workers.

Added: Nov 30, 2025

1057. What is `WebGL`?

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A JavaScript API for rendering high-performance 2D and 3D graphics directly in the browser, based on the OpenGL ES standard.

Added: Nov 30, 2025

1058. What is the `WebGPU` API?

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A modern browser API designed to expose the capabilities of device graphics hardware (GPU) for rendering and general-purpose computation, intended as a successor to WebGL.

Added: Nov 30, 2025

1059. What is the `Web Neural Network API (WebNN)`?

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A proposed API that provides hardware-accelerated access to a device's neural network capabilities, allowing web developers to run machine learning models efficiently in the browser.

Added: Nov 30, 2025

1060. What is the `HTML Drag and Drop API`?

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A set of events and interfaces that enable drag-and-drop functionality within a web application, allowing users to move elements or files.

Added: Nov 30, 2025

1061. What is the purpose of the `dataTransfer` object in Drag and Drop?

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An object that holds the data that is being dragged, specifies the drag operation type, and allows access to the list of files being dragged.

Added: Nov 30, 2025

1062. What is the `Focus Ring`?

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The visual indicator (often a glow or border) displayed around an interactive element when it receives keyboard focus, essential for accessibility.

Added: Nov 30, 2025

1063. What is the `:focus-visible` pseudo-class?

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A CSS pseudo-class that selectively applies focus styles only when the browser determines that the focus indicator is helpful to the user (e.g., when tabbing, but not when clicking).

Added: Nov 30, 2025

1064. What is the `role="alert"` ARIA attribute?

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A live region role that is used for important, time-sensitive information that should be immediately presented to the user (e.g., an error message).

Added: Nov 30, 2025

1065. What is the `aria-describedby` attribute?

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An ARIA attribute that specifies the ID of the element(s) that provide a description for the current element (similar to a tooltip or extended help text).

Added: Nov 30, 2025

1066. What is `Cognitive Load` in UX/UI design?

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The total amount of mental effort that is required to use a product or system, which should be minimized for good usability.

Added: Nov 30, 2025

1067. What is `A/B Testing` (Split Testing)?

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A method of comparing two versions of a webpage or app feature against each other to determine which one performs better in converting or engaging users.

Added: Nov 30, 2025

1068. What is `Feature Flagging` (Toggling)?

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A software development technique that allows teams to modify system behavior without changing the code, typically used to roll out features gradually or conduct A/B tests.

Added: Nov 30, 2025

1069. What is `Web Hooks`?

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User-defined HTTP callbacks that are triggered by a specific event in a web application (e.g., a commit to a repository), allowing automated communication between services.

Added: Nov 30, 2025

1070. What is `Long Polling`?

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A technique where the client connects to the server and keeps the connection open until new data is available, at which point the server sends the data and closes the connection, forcing the client to immediately reconnect.

Added: Nov 30, 2025

1071. How does `WebSockets` compare to `Long Polling`?

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WebSockets use a single, persistent, full-duplex TCP connection, allowing the server to push data efficiently. Long Polling requires the client to reconnect after every message or timeout.

Added: Nov 30, 2025

1072. What is the `requestAnimationFrame` method?

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A method that tells the browser you wish to perform an animation and requests the browser to call a specified function to update an animation *before* the next repaint.

Added: Nov 30, 2025

1073. Why is `requestAnimationFrame` better than `setTimeout` for animations?

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It runs exactly once per frame (usually 60fps), synchronized with the browser's repaint cycle, ensuring smooth animation and pausing when the tab is inactive, saving battery.

Added: Nov 30, 2025

1074. What is `Throttling` an event handler?

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A technique that limits the number of times a function can be executed over a period of time, often used for scroll or resize events to improve performance.

Added: Nov 30, 2025

1075. What is `Debouncing` an event handler?

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A technique that prevents a function from being called until a certain amount of time has passed since the last time it was invoked, often used for input fields (search).

Added: Nov 30, 2025

1076. What is the `HTML Media Capture` API?

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A feature that allows access to the user's device cameras and microphones directly through standard HTML form input elements (`<input type="file" accept="image/*" capture>`).

Added: Nov 30, 2025

1077. What is the purpose of the `ImageBitmap` object?

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An interface that represents a bitmap image which can be drawn onto a `<canvas>` without the need for an intermediate `<img>` element, often used for performance optimization in Web Workers.

Added: Nov 30, 2025

1078. What is the `OffscreenCanvas` API?

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An API that provides a canvas context that can be drawn to off the main thread (in a Web Worker), allowing computationally intensive rendering tasks without blocking the main thread.

Added: Nov 30, 2025

1079. What is `Web Cryptography API`?

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A browser API that provides developers with cryptographic primitives (hashing, signing, encryption, decryption) for performing secure operations on the client side.

Added: Nov 30, 2025

1080. What is `Elliptic Curve Cryptography (ECC)`?

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A public-key encryption approach that provides a high level of security with smaller key sizes compared to non-ECC methods (like RSA), common in modern TLS.

Added: Nov 30, 2025

1081. What is a `Merkle Tree` (Hash Tree)?

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A data structure in cryptography where every leaf node is labeled with the hash of a data block, and every non-leaf node is labeled with the cryptographic hash of the labels of its child nodes.

Added: Nov 30, 2025

1082. What is the `Content-DPR` header and its purpose?

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A header used in conjunction with `Accept-CH` to inform the browser about the actual device pixel ratio (DPR) of an image that was served, optimizing resource delivery.

Added: Nov 30, 2025

1083. What is `Client Hints`?

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A mechanism that allows a server to request specific information about the user's device and network (e.g., viewport width, DPR) via HTTP headers, optimizing asset delivery (e.g., using `Accept-CH`).

Added: Nov 30, 2025

1084. What is `Adaptive Loading`?

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A performance technique where the content or features loaded are dynamically adjusted based on the user's connection speed, device capabilities, or historical data.

Added: Nov 30, 2025

1085. What is `Image Segmentation` (in computer vision)?

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The process of dividing a digital image into multiple segments (sets of pixels) to simplify or change the representation of an image into something more meaningful and easier to analyze.

Added: Nov 30, 2025

1086. What is the `Virtual DOM (VDOM)`?

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A programming concept where an idealized or "virtual" representation of a UI is kept in memory and synchronized with the "real" DOM by a library like React, optimizing updates.

Added: Nov 30, 2025

1087. What is `Reconciliation` (in React/VDOM)?

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The process of comparing the new Virtual DOM tree with the previous one to efficiently determine which actual DOM elements need to be updated, minimizing direct DOM manipulation.

Added: Nov 30, 2025

1088. What is the `key` prop in React lists used for?

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It provides a stable identity to each item in a list, helping React's reconciliation algorithm identify which items have changed, been added, or been removed, ensuring correct state and performance.

Added: Nov 30, 2025

1089. What is `Flux` architecture?

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An application architecture pattern (not a framework) that focuses on a unidirectional data flow: Action -> Dispatcher -> Store -> View, primarily used with React.

Added: Nov 30, 2025

1090. What is `Redux Thunk`?

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A middleware for Redux that allows you to write action creators that return a function instead of an action object, primarily used for handling asynchronous logic (like API calls).

Added: Nov 30, 2025

1091. What is `Redux Saga`?

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A middleware for Redux that uses JavaScript Generators to handle side effects (asynchronous operations, like API calls) in a more organized, declarative, and testable way.

Added: Nov 30, 2025

1092. What is `Memoization`?

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An optimization technique used primarily to speed up computer programs by storing the results of expensive function calls and returning the cached result when the same inputs occur again.

Added: Nov 30, 2025

1093. What is the `useMemo` React Hook?

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A hook that memoizes the result of a function call, returning the cached value only if the dependencies have not changed, avoiding expensive recalculations on every render.

Added: Nov 30, 2025

1094. What is the `useCallback` React Hook?

Show Answer

A hook that memoizes the function itself, returning the same function instance on every render (unless dependencies change), which is useful for optimizing child component rendering.

Added: Nov 30, 2025

1095. What is `Next.js Middleware`?

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A feature in Next.js that allows you to run code before a request is completed, enabling you to modify the response based on the incoming request, useful for routing, authentication, and A/B testing.

Added: Nov 30, 2025

1096. What is `Static Site Generation (SSG)`?

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The process of building a website's HTML, CSS, and JavaScript files at *build time*, storing them on a CDN, and serving the static assets instantly without hitting a server during runtime.

Added: Nov 30, 2025

1097. What is `Incremental Static Regeneration (ISR)`?

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A feature in frameworks like Next.js that allows you to update static pages *after* the site has been built by defining a revalidation time, offering the benefits of SSG with dynamic updates.

Added: Nov 30, 2025

1098. What is the `useLayoutEffect` React Hook?

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A hook whose function runs synchronously **after** all DOM mutations but **before** the browser has painted, often used for reading layout from the DOM and synchronously re-rendering.

Added: Nov 30, 2025

1099. When should you use `useLayoutEffect` instead of `useEffect`?

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When you need to perform DOM measurements or modifications that must occur before the user sees the paint, preventing a visual flash or flicker.

Added: Nov 30, 2025

1100. What is `React Server Components (RSC)`?

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A new component model that allows developers to write components that run *only* on the server, leveraging server-side data fetching and reducing the client-side JavaScript bundle size.

Added: Nov 30, 2025

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