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Page 8 of 13 (Displaying Questions 701 – 800 of 1207 Total)

701. What is the `Intl.DisplayNames` API?

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An internationalization API that allows for consistent translation of language, region, script, and currency names into a user-readable display language.

Added: Nov 30, 2025

702. Explain the concept of a `Plural Rules` API.

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A feature of the `Intl` object that determines the correct plural form of a word for a given number in a specific language (e.g., zero, one, two, few, many, other).

Added: Nov 30, 2025

703. What is `Web Speech API`?

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A browser API that adds voice recognition (Speech to Text) and speech synthesis (Text to Speech) capabilities to web applications.

Added: Nov 30, 2025

704. What is the `Ambient Light Sensor API`?

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A browser API that provides access to the light level reading of the device's ambient light sensor, allowing sites to dynamically adjust contrast or themes.

Added: Nov 30, 2025

705. What is the `Proximity Sensor API`?

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A sensor API that detects how close an object is to the device, often used in mobile devices to turn off the screen when held near the user's face.

Added: Nov 30, 2025

706. Explain the `Web Locks API`.

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An API that provides a mechanism for scripts running in different tabs, workers, or frames (from the same origin) to coordinate resource access, preventing race conditions.

Added: Nov 30, 2025

707. What is the purpose of the `Screen Wake Lock API`?

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An API that prevents the device from dimming or locking the screen when an application needs to keep the display active (e.g., during a presentation or navigation).

Added: Nov 30, 2025

708. What is the `Badging API`?

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A PWA API that allows installed web applications to set a numeric badge on their app icon, notifying the user of new activity without requiring a full notification.

Added: Nov 30, 2025

709. What is `Feature Detection` vs. `Browser Sniffing`?

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Feature detection checks if a specific API or property exists. Browser sniffing checks the user-agent string to identify the browser, which is unreliable and discouraged.

Added: Nov 30, 2025

710. What is the `User-Agent Client Hints` standard?

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A modern replacement for the traditional User-Agent string, providing developers with more privacy-preserving and structured access to browser/device information.

Added: Nov 30, 2025

711. Explain the `Intersection Observer API` in detail.

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An API that provides an asynchronous and performant way to observe changes in the intersection of a target element with an ancestor element or the top-level viewport.

Added: Nov 30, 2025

712. What is the `Resize Observer API`?

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An API that allows developers to efficiently track changes to the size of an element's content or border box, often used for dynamic layout adjustments.

Added: Nov 30, 2025

713. What is the JavaScript `Symbol` primitive type?

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A unique and immutable data type, often used to create unique object property keys that are guaranteed not to clash with keys from other code.

Added: Nov 30, 2025

714. What are `Well-Known Symbols`?

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Built-in symbols (like `Symbol.iterator`, `Symbol.toStringTag`) that are used by JavaScript engines to define and access internal language behaviors.

Added: Nov 30, 2025

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

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A meta-property available inside functions and constructors that tells you whether the function was called with the `new` keyword, used for implementing abstract classes.

Added: Nov 30, 2025

716. Explain the `try...catch...finally` block behavior with respect to the `finally` block.

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The `finally` block always executes, regardless of whether an exception was thrown or caught in the `try` or `catch` blocks.

Added: Nov 30, 2025

717. What is a `First-Class Function`?

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A language feature where functions are treated as first-class citizens, meaning they can be assigned to variables, passed as arguments, and returned from other functions.

Added: Nov 30, 2025

718. What is the `Singleton Pattern` in JavaScript?

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A design pattern that restricts the instantiation of a class to a single object, ensuring that only one instance of the object exists throughout the application.

Added: Nov 30, 2025

719. Explain the `Revealing Module Pattern`.

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A JavaScript design pattern that encapsulates all private members and exposes only the public parts of the module through a returned object literal, ensuring clear separation.

Added: Nov 30, 2025

720. What is `Currying` in JavaScript?

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A technique of transforming a function that takes multiple arguments into a sequence of functions, each taking a single argument.

Added: Nov 30, 2025

721. What is the `Flux` architecture pattern?

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An application architecture (popularized by React) that enforces a unidirectional data flow (View -> Action -> Dispatcher -> Store -> View), simplifying state management.

Added: Nov 30, 2025

722. What is the benefit of `Immutable Data Structures` in state management?

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They simplify change detection (by reference comparison) and ensure predictable state updates, which reduces complexity and improves performance in rendering.

Added: Nov 30, 2025

723. What is the `Serverless` computing model?

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A cloud execution model where the cloud provider dynamically manages the server resources (provisioning, scaling, maintenance), allowing the developer to focus only on writing code.

Added: Nov 30, 2025

724. What is `FaaS (Function as a Service)`?

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A category of cloud computing that provides a platform allowing customers to develop, run, and manage application functionalities without the complexity of building and maintaining the infrastructure.

Added: Nov 30, 2025

725. What are `cold starts` in Serverless functions?

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The latency incurred when a serverless function that has been idle needs to be provisioned and initialized (loading runtime, code, and configuration) before it can handle a request.

Added: Nov 30, 2025

726. Explain the `Backend as a Service (BaaS)` model.

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A cloud service model that provides ready-made backend services (user management, databases, file storage) allowing frontend developers to focus solely on the client-side code.

Added: Nov 30, 2025

727. What is the `Jamstack` architecture?

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

Added: Nov 30, 2025

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

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A rendering method that allows for the building of static pages at build time, but also enables them to be re-rendered (regenerated) on demand or at timed intervals, blending SSG and SSR.

Added: Nov 30, 2025

729. What is `Edge Functions`?

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Serverless functions that run at the Content Delivery Network (CDN) edge locations, closer to the user, reducing latency for dynamic content and personalized responses.

Added: Nov 30, 2025

730. What is `Digital Accessibility`?

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The practice of ensuring that digital content (websites, apps) can be easily perceived, operated, and understood by people with disabilities.

Added: Nov 30, 2025

731. What are the four principles of WCAG?

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Perceivable, Operable, Understandable, and Robust (P.O.U.R.).

Added: Nov 30, 2025

732. What is the `tabindex` attribute used for in accessibility?

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It modifies the tab order of elements and allows non-interactive elements to be focusable, primarily for keyboard navigation.

Added: Nov 30, 2025

733. What is the purpose of `aria-labelledby`?

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An ARIA attribute used to associate a non-interactive element (like a custom control) with the label provided by another element on the page, improving context for screen readers.

Added: Nov 30, 2025

734. How do you correctly hide an element visually while keeping it available for screen readers?

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By using an accessibility class with CSS properties like `clip: rect(0 0 0 0);`, `width: 1px;`, `height: 1px;`, and `overflow: hidden;`.

Added: Nov 30, 2025

735. What is `Color Contrast Ratio` and its WCAG requirement?

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The difference in luminance between the foreground text color and the background color. WCAG requires a minimum ratio of 4.5:1 for normal text.

Added: Nov 30, 2025

736. What is the `Web Performance Budget`?

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A set of measurable constraints on the size, quantity, and load time of assets (like JavaScript, images) that the development team agrees not to exceed to maintain performance goals.

Added: Nov 30, 2025

737. What is the `Speed Index` performance metric?

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A metric that measures how quickly the contents of a page are visibly populated, with a lower score being better.

Added: Nov 30, 2025

738. Explain the concept of `Taint Checking` in security.

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A technique where data from an untrusted source is "tainted" to prevent it from being used in sensitive sinks (like `eval()` or database queries) unless it is properly sanitized.

Added: Nov 30, 2025

739. What is a `security sandbox`?

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A security mechanism that isolates running programs, restricting the resources (like file systems or network access) that the application can access.

Added: Nov 30, 2025

740. What is `OWASP Top 10`?

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A standard awareness document for developers and web application security, representing a broad consensus about the most critical security risks to web applications.

Added: Nov 30, 2025

741. What is the difference between `Symmetric` and `Asymmetric` encryption?

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Symmetric uses a single secret key for both encryption and decryption. Asymmetric uses a pair of public and private keys for security.

Added: Nov 30, 2025

742. What is a `Key Derivation Function (KDF)`?

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A cryptographic hash function that derives one or more secret keys from a secret value, like a password or master key, used to make dictionary attacks harder.

Added: Nov 30, 2025

743. How do you handle secrets (API keys, tokens) in a serverless function?

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By storing them in secure, centralized secret management services (like AWS Secrets Manager or Azure Key Vault) and retrieving them at runtime.

Added: Nov 30, 2025

744. What is the `Adapter Pattern` (or Wrapper) in JavaScript design?

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A structural pattern that converts the interface of a class into another interface that clients expect, allowing classes with incompatible interfaces to work together.

Added: Nov 30, 2025

745. Explain the `Facade Pattern`.

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A structural pattern that provides a simplified interface to a large body of code (a library or subsystem), shielding the client from the complexity of the internal components.

Added: Nov 30, 2025

746. What is the `Decorator Pattern` in JavaScript?

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A structural pattern that dynamically attaches additional responsibilities to an object, providing a flexible alternative to subclassing for extending functionality.

Added: Nov 30, 2025

747. What is `Dependency Injection (DI)`?

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A design pattern where components receive their dependencies from an external source (like a framework or container) rather than creating them themselves, increasing modularity and testability.

Added: Nov 30, 2025

748. What is the concept of a `Render Prop` pattern?

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A component-based pattern where a component takes a function (the render prop) as a prop, which it calls to determine what to render, enabling sharing of stateful logic.

Added: Nov 30, 2025

749. Explain the purpose of `React Hooks` (conceptually).

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A feature that allows functional components to "hook into" (use) state and lifecycle features without needing to convert them to class components, promoting reuse of stateful logic.

Added: Nov 30, 2025

750. What are `memoized selectors` (e.g., Reselect) used for in state management?

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They prevent unnecessary recalculations of derived data when the input state has not changed, improving performance in complex state trees.

Added: Nov 30, 2025

751. What is the benefit of `server-side rendering (SSR)` over client-side rendering (CSR)?

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SSR provides faster First Contentful Paint (FCP) and better SEO, as the initial HTML is fully formed and crawlable by search engines.

Added: Nov 30, 2025

752. What is the `Web Worker` limit?

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There is generally no formal specification limit, but modern browsers typically limit the number of active workers to around 20 for performance reasons, with more being queued.

Added: Nov 30, 2025

753. How do you pass data between a Service Worker and the main thread?

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Using the `postMessage()` method via the `MessageChannel` or the Service Worker's registration object.

Added: Nov 30, 2025

754. What is the purpose of the `Notification.permission` property?

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It provides the current permission status for displaying notifications to the user (e.g., `default`, `granted`, or `denied`).

Added: Nov 30, 2025

755. Explain the `window.postMessage()` method.

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A method that enables secure cross-origin communication between `Window` objects (e.g., between an iframe and its parent, or two different windows).

Added: Nov 30, 2025

756. What is the role of `Trusted Types` (browser security feature)?

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A security mechanism that requires certain APIs (like `innerHTML`) to only accept pre-sanitized input, mitigating DOM-based XSS vulnerabilities.

Added: Nov 30, 2025

757. How does `WebAuthn` (Web Authentication API) work?

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It enables users to authenticate to a web application using hardware authenticators (e.g., security keys, biometrics) instead of passwords, leveraging public-key cryptography.

Added: Nov 30, 2025

758. What is the difference between `localStorage` and `sessionStorage`?

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`localStorage` persists data across browser sessions and tabs. `sessionStorage` clears data when the browser tab or window is closed.

Added: Nov 30, 2025

759. What is the size limit for `localStorage`?

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Typically 5MB to 10MB per origin, depending on the browser.

Added: Nov 30, 2025

760. What is the purpose of the `window.location.assign()` method?

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It loads a new document at the specified URL, similar to setting `window.location.href`, but explicitly indicates an intent to navigate.

Added: Nov 30, 2025

761. What is the `window.history.pushState()` method used for?

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It adds a state to the browser's session history stack without loading a new document, allowing for client-side routing in SPAs.

Added: Nov 30, 2025

762. How do you check if a browser is running offline?

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By inspecting the `navigator.onLine` property, which returns a boolean indicating the network status.

Added: Nov 30, 2025

763. What is the purpose of the `<datalist>` element?

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It provides a set of pre-defined options for an `<input>` element, offering suggestions to the user as they type.

Added: Nov 30, 2025

764. What is the difference between `<time>` and `<input type="time">`?

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`<time>` is a semantic element for marking up human-readable dates/times. `<input type="time">` is a form control for user input of time.

Added: Nov 30, 2025

765. How do you define a custom animation keyframe set in CSS?

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Using the `@keyframes` rule, followed by the animation name and a set of keyframe rules (e.g., `from`/`to` or percentage selectors).

Added: Nov 30, 2025

766. What is the purpose of `animation-fill-mode`?

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It specifies which values are applied to the element before the animation starts or after it finishes (e.g., `forwards` to keep the end state).

Added: Nov 30, 2025

767. What is the CSS `clip-path` property?

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A property that allows you to specify a clipping region, determining which parts of an element should be visible, creating custom shapes.

Added: Nov 30, 2025

768. What is the `text-wrap: balance` property (future CSS)?

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A future CSS property designed to optimize the line breaks in short blocks of text (like headings) to create a more aesthetically balanced appearance.

Added: Nov 30, 2025

769. What is the `hyphens` CSS property?

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A property that controls how words should be hyphenated when text wraps across multiple lines, improving text layout and readability.

Added: Nov 30, 2025

770. What is the purpose of the `::first-line` pseudo-element?

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It allows you to apply styles to the first formatted line of a paragraph of text.

Added: Nov 30, 2025

771. Explain the purpose of the `<picture>` element.

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It allows developers to supply multiple `<source>` elements for different image files, letting the browser choose the most appropriate one based on screen size, resolution, or format support.

Added: Nov 30, 2025

772. What is the HTML attribute `srcset` for on an `<img>` tag?

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It provides a comma-separated list of image sources and descriptors (width or pixel density) to allow the browser to select the best image for the current context.

Added: Nov 30, 2025

773. What is the `sizes` attribute used for with `srcset`?

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It tells the browser the intended display size of the image (e.g., `(max-width: 600px) 100vw, 50vw`), enabling it to calculate the optimal image from the `srcset` before layout.

Added: Nov 30, 2025

774. What is the difference between `em` and `rem` units in CSS?

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`em` is relative to the font-size of its *parent element*. `rem` (root em) is relative only to the font-size of the *root HTML element*.

Added: Nov 30, 2025

775. What are `Viewport Units` (vw, vh, vmin, vmax)?

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CSS units that are relative to the size of the viewport: `vw` (viewport width), `vh` (viewport height), `vmin` (minimum of vw/vh), and `vmax` (maximum of vw/vh).

Added: Nov 30, 2025

776. Explain the concept of `CSS Logical Properties`.

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CSS properties that define measurements based on flow direction (e.g., `margin-inline-start` instead of `margin-left` or `margin-right`), supporting internationalization and LTR/RTL layouts.

Added: Nov 30, 2025

777. What is the Node.js `libuv` library?

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A multi-platform support library written in C that provides Node.js with its non-blocking I/O operations by handling the event loop, thread pool, and file system tasks.

Added: Nov 30, 2025

778. Explain the purpose of the `Node.js Event Loop`.

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It is the mechanism that handles asynchronous callbacks in Node.js. It checks queues (timers, I/O, microtasks) and pushes functions onto the call stack when the stack is empty.

Added: Nov 30, 2025

779. What is the `Node.js Thread Pool`?

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A set of worker threads managed by `libuv` (typically four threads) used to handle blocking system calls like file I/O and DNS lookup, preventing the main event loop from stalling.

Added: Nov 30, 2025

780. What is the `Z-index` property in CSS and how is its stacking context determined?

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It specifies the stack order of an element. The stacking context is determined by elements with properties like `position: relative|absolute|fixed|sticky` (if not 0) or certain CSS transforms/filters.

Added: Nov 30, 2025

781. Explain the CSS `calc()` function.

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A functional notation that allows mathematical expressions to be used for property values, mixing different units (e.g., `width: calc(100% - 20px)`).

Added: Nov 30, 2025

782. What is the difference between CSS `grid` and `flexbox`?

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Flexbox is designed for one-dimensional layout (row or column). Grid is designed for two-dimensional layout (rows and columns simultaneously).

Added: Nov 30, 2025

783. What is `grid-area` used for in CSS Grid?

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A shorthand property that defines a grid item's size and location in a single declaration, often used in conjunction with named grid areas.

Added: Nov 30, 2025

784. What is the CSS `minmax()` function?

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A function used in CSS Grid properties (`grid-template-columns`/`rows`) to define a range of minimum and maximum sizes for a grid track.

Added: Nov 30, 2025

785. Explain the purpose of `display: contents` in CSS.

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It makes the container element disappear from the box model, causing its children to become direct children of the container's parent, affecting layout and accessibility.

Added: Nov 30, 2025

786. What is the CSS `line-clamp` property (non-standard)?

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A property primarily used by WebKit browsers to limit the content of a block element to a specific number of lines, displaying an ellipsis if truncated.

Added: Nov 30, 2025

787. What is the `content-visibility` CSS property?

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A property that controls whether an element renders its content, allowing the user agent to skip its layout and painting work if it is not relevant, significantly boosting rendering performance.

Added: Nov 30, 2025

788. What is the `gap` property in Flexbox and Grid?

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A shorthand for `row-gap` and `column-gap`, used to set the spacing between rows and columns inside Flexbox or Grid containers.

Added: Nov 30, 2025

789. Explain the concept of `CSS Houdini`.

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A set of APIs that exposes parts of the CSS engine to JavaScript, allowing developers to extend CSS by writing custom rendering code, such as worklets for layout and paint.

Added: Nov 30, 2025

790. What is a `Paint Worklet` in Houdini?

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A browser thread that allows developers to write custom CSS functions that can generate images (like background images) programmatically using JavaScript.

Added: Nov 30, 2025

791. What is the `@property` rule in CSS?

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A Houdini feature that allows developers to explicitly register and define custom CSS properties, including their syntax, initial value, and inheritance behavior.

Added: Nov 30, 2025

792. What is the JavaScript `Intl.NumberFormat` API?

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An internationalization API used to format numbers according to the rules of a specific locale, handling separators, currency symbols, and unit formats.

Added: Nov 30, 2025

793. What is the `Intl.DisplayNames` API?

Show Answer

An internationalization API that allows for consistent translation of language, region, script, and currency names into a user-readable display language.

Added: Nov 30, 2025

794. Explain the concept of a `Plural Rules` API.

Show Answer

A feature of the `Intl` object that determines the correct plural form of a word for a given number in a specific language (e.g., zero, one, two, few, many, other).

Added: Nov 30, 2025

795. What is `Web Speech API`?

Show Answer

A browser API that adds voice recognition (Speech to Text) and speech synthesis (Text to Speech) capabilities to web applications.

Added: Nov 30, 2025

796. What is the `Ambient Light Sensor API`?

Show Answer

A browser API that provides access to the light level reading of the device's ambient light sensor, allowing sites to dynamically adjust contrast or themes.

Added: Nov 30, 2025

797. What is the `Proximity Sensor API`?

Show Answer

A sensor API that detects how close an object is to the device, often used in mobile devices to turn off the screen when held near the user's face.

Added: Nov 30, 2025

798. Explain the `Web Locks API`.

Show Answer

An API that provides a mechanism for scripts running in different tabs, workers, or frames (from the same origin) to coordinate resource access, preventing race conditions.

Added: Nov 30, 2025

799. What is the purpose of the `Screen Wake Lock API`?

Show Answer

An API that prevents the device from dimming or locking the screen when an application needs to keep the display active (e.g., during a presentation or navigation).

Added: Nov 30, 2025

800. What is the `Badging API`?

Show Answer

A PWA API that allows installed web applications to set a numeric badge on their app icon, notifying the user of new activity without requiring a full notification.

Added: Nov 30, 2025

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