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Page 10 of 13 (Displaying Questions 901 – 1000 of 1207 Total)

901. What is the `Service Worker lifecycle`?

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The sequence of events a Service Worker goes through: downloaded, installing, installed, activating, activated, and redundant (or fetching, if an update is found).

Added: Nov 30, 2025

902. What is the purpose of `clients.claim()` in a Service Worker?

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It allows an *active* Service Worker to immediately take control of clients (pages/tabs) that are within its scope but were opened *before* the Service Worker was activated.

Added: Nov 30, 2025

903. What is the Service Worker `fetch` event?

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The primary event in a Service Worker, fired every time a resource within the worker's scope is requested, allowing the worker to intercept and respond to network requests.

Added: Nov 30, 2025

904. How do you check if a browser supports Service Workers?

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By checking the existence of `navigator.serviceWorker` in the global `window` object.

Added: Nov 30, 2025

905. What is `IndexedDB`?

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A low-level, transactional, high-performance database system built into the browser for storing large amounts of structured data on the client side.

Added: Nov 30, 2025

906. How does `IndexedDB` differ from `localStorage`?

Show Answer

IndexedDB is transactional, asynchronous, and supports complex data structures and indexes, with much larger storage limits. `localStorage` is synchronous, key-value storage for small amounts of simple data.

Added: Nov 30, 2025

907. What is the `Web Streams API`?

Show Answer

An API that allows JavaScript to process data (such as network responses or local files) in small, sequential chunks, enabling efficient, non-blocking reading, writing, and transformation of data.

Added: Nov 30, 2025

908. What are `Readable Streams`?

Show Answer

An interface in the Streams API representing a source of data that can be read one chunk at a time, allowing consumption of data while it is still being fetched (e.g., a network response).

Added: Nov 30, 2025

909. What is the `TransformStream` interface?

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An interface in the Streams API that represents a stream that transforms data, where the output is a `ReadableStream` and the input is a `WritableStream`.

Added: Nov 30, 2025

910. Explain the purpose of the `AbortController` and `AbortSignal`.

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A mechanism used to abort one or more asynchronous requests (e.g., `fetch`, `Web Workers`) by signaling cancellation, allowing for cleaner resource management and error handling.

Added: Nov 30, 2025

911. What is `HTTP Pipelining` (in HTTP/1.1) and why is it problematic?

Show Answer

It allowed clients to send multiple requests on the same connection without waiting for each response. It was often disabled due to implementation complexities and its susceptibility to HOL blocking.

Added: Nov 30, 2025

912. What is the `Expect-CT` HTTP header?

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A security header that forces the browser to check that a server's certificate is publicly logged via Certificate Transparency logs, protecting against misissued or malicious certificates.

Added: Nov 30, 2025

913. What is the `Referrer-Policy` header?

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An HTTP header that controls the amount of referrer information (the previous page URL) sent with requests originating from the document.

Added: Nov 30, 2025

914. What is `Third-Party Script Blocking`?

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A performance optimization technique where scripts from third-party domains (like ads, analytics) are prevented from executing until after the page's critical content has loaded.

Added: Nov 30, 2025

915. How does `PartyTown` optimize third-party script loading?

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It uses Web Workers to offload the execution of third-party scripts (like Google Analytics) from the main thread to a separate worker thread, eliminating main thread contention (jank).

Added: Nov 30, 2025

916. What is the `Document-Policy` HTTP header?

Show Answer

A proposed header that allows a document to selectively disable certain browser features (e.g., synchronous scripts, large image decoding) to improve performance.

Added: Nov 30, 2025

917. What is `Web of Trust` in the context of SSL/TLS?

Show Answer

A decentralized concept where individuals verify the authenticity of other users' public keys, contrasting with the centralized system of Certificate Authorities (CAs).

Added: Nov 30, 2025

918. What is a `Heartbleed` vulnerability?

Show Answer

A catastrophic security bug in the OpenSSL cryptographic software library (in 2014) that allowed attackers to read the memory of systems protected by vulnerable versions of the SSL/TLS protocol.

Added: Nov 30, 2025

919. What is `Perfect Forward Secrecy (PFS)`?

Show Answer

A property of cryptographic protocols that ensures that if a session key is compromised, it will not compromise any past or future session keys, usually achieved using ephemeral Diffie-Hellman.

Added: Nov 30, 2025

920. What is `Symmetric Encryption`?

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An encryption scheme where the same key is used to encrypt and decrypt the data, making it fast but requiring a secure channel to share the key.

Added: Nov 30, 2025

921. What is `Asymmetric Encryption`?

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An encryption scheme that uses a pair of mathematically linked keys (a public key for encryption and a private key for decryption), used to securely establish the shared secret key in SSL/TLS.

Added: Nov 30, 2025

922. What is `Deno` and how does it differ from Node.js?

Show Answer

A secure JavaScript/TypeScript runtime built with Rust and V8, focusing on security (sandboxed execution, explicit permissions) and modern standards (ES Modules by default).

Added: Nov 30, 2025

923. What is `Bun` and its main differentiator?

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A new, fast JavaScript runtime built with the Zig language, designed to be an all-in-one toolkit (runtime, bundler, package manager) with emphasis on speed and developer experience.

Added: Nov 30, 2025

924. What is the `Event Loop Tick` (in Node.js)?

Show Answer

A single iteration of the Node.js Event Loop, during which it processes one microtask queue, then one macrotask queue (timer, I/O, poll, etc.), before repeating.

Added: Nov 30, 2025

925. What is the purpose of `process.nextTick()` in Node.js?

Show Answer

It schedules a callback function to be executed at the end of the current phase of the event loop, but *before* the I/O queue or any timers are processed, essentially running immediately after the current code finishes.

Added: Nov 30, 2025

926. What is `Cluster Mode` in Node.js?

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A module that allows for creating child processes that share the same server port, enabling load balancing and leveraging multiple CPU cores to improve throughput.

Added: Nov 30, 2025

927. What is `GraphQL Schema Stitching`?

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The process of combining multiple independent GraphQL schemas into a single unified schema that clients can query, simplifying communication across different services.

Added: Nov 30, 2025

928. What is `GraphQL Federation`?

Show Answer

A newer, more scalable approach to combining multiple GraphQL services where each service owns a portion of the total schema and is responsible for resolving its own fields.

Added: Nov 30, 2025

929. What is the `Back-end for Frontend (BFF)` pattern?

Show Answer

An architectural pattern where a separate backend service is created for each frontend application (e.g., one for web, one for mobile), optimizing data delivery for that specific client.

Added: Nov 30, 2025

930. What is the `Circuit Breaker` pattern?

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A resilience pattern used in distributed systems that prevents an application from repeatedly trying to execute an operation that is likely to fail, giving the service time to recover.

Added: Nov 30, 2025

931. What is `Chaos Engineering`?

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The discipline of experimenting on a system in order to build confidence in the system's capability to withstand turbulent conditions in production.

Added: Nov 30, 2025

932. What is the `Service Locator` pattern?

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A software design pattern that encapsulates the process of locating a service by abstracting it from the client, often contrasting with the Dependency Injection pattern.

Added: Nov 30, 2025

933. What is `Web of Trust` in the context of SSL/TLS?

Show Answer

A decentralized concept where individuals verify the authenticity of other users' public keys, contrasting with the centralized system of Certificate Authorities (CAs).

Added: Nov 30, 2025

934. What is the `aria-live` attribute?

Show Answer

An ARIA attribute that indicates that an element's content is likely to change dynamically and informs screen readers how important the change is (e.g., `polite` or `assertive`).

Added: Nov 30, 2025

935. What is the difference between `aria-live="polite"` and `aria-live="assertive"`?

Show Answer

`polite` announces updates when the user is idle. `assertive` interrupts the user's current task to announce the update immediately (use sparingly).

Added: Nov 30, 2025

936. What is the `Accessibility Object Model (AOM)`?

Show Answer

A set of APIs that allows developers to expose and manipulate the accessibility tree directly, complementing the DOM and CSSOM.

Added: Nov 30, 2025

937. What is `Focus Management` in web accessibility?

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The practice of ensuring that the keyboard focus is handled correctly, especially during dynamic updates (e.g., opening a modal, focusing the close button).

Added: Nov 30, 2025

938. How do you correctly handle modal accessibility?

Show Answer

By trapping the keyboard focus inside the modal when it is open, hiding the rest of the page from assistive technology, and returning focus to the trigger element when closed.

Added: Nov 30, 2025

939. What is the `Content-Visibility` CSS property?

Show Answer

A property that allows the user agent to skip an element's rendering work (layout and painting) if it is not relevant, significantly boosting initial load and rendering performance.

Added: Nov 30, 2025

940. Explain the purpose of the `WebAssembly System Interface (WASI)`.

Show Answer

A modular system interface for WebAssembly, designed to run Wasm outside the browser (e.g., on servers or IoT devices) in a secure, sandboxed environment.

Added: Nov 30, 2025

941. What is the difference between `WebAssembly` and `Docker`?

Show Answer

WebAssembly provides a secure, lightweight sandboxed environment for code execution *within* a process. Docker provides containerization, isolating entire *operating systems* and processes.

Added: Nov 30, 2025

942. What is `Server-Side Rendering (SSR)`?

Show Answer

The process of rendering a client-side application to regular HTML on the server and sending the fully rendered page to the client, improving initial load performance and SEO.

Added: Nov 30, 2025

943. What is `Hydration` in the context of SSR?

Show Answer

The process where the client-side JavaScript takes over the server-rendered HTML and attaches event handlers and state, making the static page interactive.

Added: Nov 30, 2025

944. What is `Isomorphic/Universal JavaScript`?

Show Answer

Code that can run both on the client (browser) and the server (Node.js), often used to enable Server-Side Rendering (SSR) for initial page loads.

Added: Nov 30, 2025

945. What is `Time to First Byte (TTFB)`?

Show Answer

A fundamental performance metric that measures the time between the client sending a request and receiving the first byte of the response from the server.

Added: Nov 30, 2025

946. What is the `Long Task API`?

Show Answer

A JavaScript API that reports any task that executes on the main thread for 50 milliseconds or longer, which is critical for diagnosing and optimizing for Total Blocking Time (TBT).

Added: Nov 30, 2025

947. What is the browser `Compositor Thread` responsible for?

Show Answer

The process that takes the rendered layers from the main thread, composites them into a single frame, and sends them to the screen, often handling high-performance animations (transforms, opacity).

Added: Nov 30, 2025

948. How do you force hardware acceleration in CSS?

Show Answer

By using properties that the browser typically handles on the Compositor Thread, such as `transform: translateZ(0)` (the null transform trick) or `will-change: transform`.

Added: Nov 30, 2025

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

Show Answer

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

950. What is the `Navigation Timing API`?

Show Answer

A performance API that provides data points related to the navigation and load events of a document, allowing for detailed measurement of network and rendering delays.

Added: Nov 30, 2025

951. What is the `Resource Timing API`?

Show Answer

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

952. What is `Web Vitals`?

Show Answer

A set of unified guidelines from Google for quality signals that are essential to delivering a great user experience on the web (LCP, FID/INP, CLS).

Added: Nov 30, 2025

953. What is `First Input Delay (FID)`?

Show Answer

A performance metric that measures the time from when a user first interacts with a page (e.g., clicks a button) to the moment the browser is able to begin processing event handlers.

Added: Nov 30, 2025

954. What is the `Cache API` used for in Service Workers?

Show Answer

A powerful, promise-based API that provides programmatic control over a collection of `Request`/`Response` object pairs, used for caching assets for offline support.

Added: Nov 30, 2025

955. What is the `Service Worker lifecycle`?

Show Answer

The sequence of events a Service Worker goes through: downloaded, installing, installed, activating, activated, and redundant (or fetching, if an update is found).

Added: Nov 30, 2025

956. What is the purpose of `clients.claim()` in a Service Worker?

Show Answer

It allows an *active* Service Worker to immediately take control of clients (pages/tabs) that are within its scope but were opened *before* the Service Worker was activated.

Added: Nov 30, 2025

957. What is the `Web Streams API`?

Show Answer

An API that allows JavaScript to process data (such as network responses or local files) in small, sequential chunks, enabling efficient, non-blocking reading, writing, and transformation of data.

Added: Nov 30, 2025

958. What are `Readable Streams`?

Show Answer

An interface in the Streams API representing a source of data that can be read one chunk at a time, allowing consumption of data while it is still being fetched (e.g., a network response).

Added: Nov 30, 2025

959. Explain the purpose of the `AbortController` and `AbortSignal`.

Show Answer

A mechanism used to abort one or more asynchronous requests (e.g., `fetch`, `Web Workers`) by signaling cancellation, allowing for cleaner resource management and error handling.

Added: Nov 30, 2025

960. What is `JSON-LD (JSON for Linking Data)`?

Show Answer

A lightweight Linked Data format used to create machine-readable metadata in JSON format, often embedded in HTML via a `<script type="application/ld+json">` tag for SEO.

Added: Nov 30, 2025

961. What is the HTML `rel="noopener"` attribute?

Show Answer

An attribute added to links (`<a>` tags) that prevents the opened page from being able to access the originating window via `window.opener`, mitigating reverse tabnabbing attacks.

Added: Nov 30, 2025

962. What is `reverse tabnabbing`?

Show Answer

A security vulnerability where a page linked from your site can use `window.opener` to navigate your page to a malicious phishing site.

Added: Nov 30, 2025

963. What is the `inert` HTML attribute?

Show Answer

A global attribute (currently a proposal) that makes an element and all its descendants non-interactive and hidden from assistive technologies, effectively disabling the content.

Added: Nov 30, 2025

964. What is `aria-roledescription`?

Show Answer

An ARIA attribute used to provide a more specific, human-readable description of an element's role, often used to clarify custom widgets to screen reader users.

Added: Nov 30, 2025

965. What is the `rel="modulepreload"` link tag?

Show Answer

A resource hint that tells the browser to fetch and compile a JavaScript module in parallel, ready for execution, optimizing the loading time of ES modules.

Added: Nov 30, 2025

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

Show Answer

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

967. What is the `WebGPU` API?

Show Answer

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

968. What is `WAI-ARIA Authoring Practices` (APG)?

Show Answer

A guide that provides developers with examples and recommended techniques for building accessible components and widgets using ARIA attributes.

Added: Nov 30, 2025

969. What is `Federated Identity`?

Show Answer

An arrangement between multiple independent organizations that allows users to use the same set of credentials (username and password) to access the applications of all organizations.

Added: Nov 30, 2025

970. What is `Single Sign-On (SSO)`?

Show Answer

An authentication process that allows a user to access multiple independent software systems with one set of login credentials.

Added: Nov 30, 2025

971. What is the `Service Mesh` architecture?

Show Answer

A dedicated infrastructure layer for handling service-to-service communication in a microservices architecture, managing security, resilience, and observability.

Added: Nov 30, 2025

972. What is `Canary Deployment`?

Show Answer

A deployment strategy that rolls out a new version of an application to a small subset of users (the "canary") before making it available to the entire user base, minimizing risk.

Added: Nov 30, 2025

973. What is the JavaScript `use strict` directive?

Show Answer

A directive that enables strict mode, instructing the JavaScript engine to execute code in a "strict" manner, helping to prevent common coding errors and "unsafe" actions.

Added: Nov 30, 2025

974. What is the `navigator.clipboard` API?

Show Answer

A modern, secure, and asynchronous API for reading and writing content to the system clipboard, replacing the older and deprecated `document.execCommand()` for copy/cut.

Added: Nov 30, 2025

975. What is `Web Vitals`?

Show Answer

A set of unified guidelines from Google for quality signals that are essential to delivering a great user experience on the web (LCP, FID/INP, CLS).

Added: Nov 30, 2025

976. What is `Input Latency`?

Show Answer

The delay between a user input action (e.g., clicking a button) and the resulting visual response on the screen.

Added: Nov 30, 2025

977. What is `Layout Shift`?

Show Answer

The unexpected movement of visual page content, a key component of the Cumulative Layout Shift (CLS) metric, often caused by resources loading asynchronously above visible content.

Added: Nov 30, 2025

978. What is the purpose of the `rel="alternate"` link tag?

Show Answer

It indicates that the current document has an alternative version, often used for providing translated pages, different media types (e.g., print), or RSS feeds.

Added: Nov 30, 2025

979. What is the HTML `download` attribute?

Show Answer

An attribute added to an `<a>` tag that, when present, instructs the browser to download the linked resource instead of navigating to it, often suggesting a file name.

Added: Nov 30, 2025

980. What is `Web Audio API`?

Show Answer

A powerful JavaScript API for processing and synthesizing audio in web applications, allowing for complex effects, mixing, and spatial audio.

Added: Nov 30, 2025

981. What is the `AudioContext` in Web Audio API?

Show Answer

The primary object in the API, representing an audio-processing graph built from audio modules (nodes) connected together.

Added: Nov 30, 2025

982. What is the `requestVideoFrameCallback` API?

Show Answer

An API that provides a callback at the time a video frame is actually displayed on the user's screen, allowing for precise synchronization of web content with video playback.

Added: Nov 30, 2025

983. What is the `requestDevice()` method in Web Bluetooth?

Show Answer

The entry point for the Web Bluetooth API, prompting the user to select a nearby Bluetooth Low Energy (BLE) device to connect to.

Added: Nov 30, 2025

984. What is the `Prioritized Task Scheduling API` (or `isInputPending`)?

Show Answer

A browser API that allows developers to check if a user input event is pending, enabling them to yield control back to the main thread quickly to keep the UI responsive.

Added: Nov 30, 2025

985. What is the purpose of the `speculationrules` script type?

Show Answer

An HTML extension that allows a developer to declaratively tell the browser which pages should be prefetched or prerendered, improving navigation speed for likely next clicks.

Added: Nov 30, 2025

986. How does `bfcache` (Back/Forward Cache) improve navigation performance?

Show Answer

It caches the entire state of a page (including the JavaScript heap and DOM) in memory, allowing instant navigation when the user uses the browser's back or forward buttons.

Added: Nov 30, 2025

987. What is the `pageshow` event?

Show Answer

An event fired when a document is first loaded or when it is retrieved from the `bfcache` (Back/Forward Cache). It is used to detect when a page is restored from cache.

Added: Nov 30, 2025

988. What is `Web Share Target API`?

Show Answer

A PWA feature that allows a web application to register itself as a share target, enabling users to share data from other native applications (or web apps) directly to the PWA.

Added: Nov 30, 2025

989. What is the `Payment Request API`?

Show Answer

A standardized browser API that provides a simple and consistent way for users to provide payment and shipping information for purchasing goods and services online.

Added: Nov 30, 2025

990. What is the `Credential Management API`?

Show Answer

An API that provides an interface for the browser to seamlessly store and retrieve credentials for a user, enabling single sign-on experiences and integration with password managers.

Added: Nov 30, 2025

991. What is `Feature Policy` (now `Permissions Policy`)?

Show Answer

An HTTP header or HTML attribute that allows a developer to explicitly allow or deny the use of certain browser features (e.g., camera, microphone, fullscreen) in their own frame and descendant iframes.

Added: Nov 30, 2025

992. What is `Reporting API`?

Show Answer

A centralized API that allows web applications to report various issues to a designated endpoint, such as Content Security Policy (CSP) violations, deprecation warnings, or intervention reports.

Added: Nov 30, 2025

993. Explain the purpose of the `Clear-Site-Data` header.

Show Answer

An HTTP response header that instructs the browser to clear various forms of data associated with the website (e.g., cookies, cache, local storage), useful for logout or migration scenarios.

Added: Nov 30, 2025

994. What is the `HTML Sanitizer API` proposal?

Show Answer

A proposed API that provides a simple and secure way to clean up potentially unsafe HTML content (e.g., from user input), mitigating XSS by removing malicious code.

Added: Nov 30, 2025

995. What is `Trusted Types`?

Show Answer

A security mechanism that requires data passed to dangerous DOM sinking functions (like `innerHTML`) to be wrapped by a policy object, effectively mitigating most DOM-based XSS attacks.

Added: Nov 30, 2025

996. How does a `Content Security Policy (CSP)` work?

Show Answer

It is an HTTP response header that defines which dynamic resources (scripts, styles, images) are trusted and allowed to be loaded by the browser, blocking unauthorized sources.

Added: Nov 30, 2025

997. What is the most restrictive `script-src` directive you can set in a CSP?

Show Answer

`script-src 'none'` or `script-src 'self'` combined with a strict hash or nonce policy.

Added: Nov 30, 2025

998. What is `Subresource Integrity (SRI)`?

Show Answer

A security feature that allows browsers to verify that resources they fetch (e.g., from a CDN) have not been tampered with by checking their cryptographic hash against a known value.

Added: Nov 30, 2025

999. What is a `Same-Origin Policy` violation?

Show Answer

When a script or document loaded from one origin attempts to interact with resources (data, DOM) from another origin without explicit permission (like CORS headers).

Added: Nov 30, 2025

1000. What is `DNS Rebinding` attack?

Show Answer

An attack where a malicious website first passes a DNS check (pointing to a benign IP) but then, using a very short TTL, rebinds the DNS to a local/private IP address, bypassing SOP.

Added: Nov 30, 2025

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