Dictionary

Focus management is the practice of controlling which element receives keyboard focus in a web application, especially during dynamic content changes. When a modal opens, focus should move into it; when it closes, focus should return to the trigger element. Proper focus management is essential for keyboard and screen reader users, and involves techniques like focus trapping, roving tabindex, and programmatic focus with `element.focus()`.

Generative AI is a category of artificial intelligence that creates new content — text, images, code, music, or video — rather than just analyzing or classifying existing data. Powered by architectures like transformers and diffusion models, generative AI has transformed software development with tools like GitHub Copilot, Claude, and Cursor. It represents a shift from AI as a classification tool to AI as a creative collaborator.

In AI, hallucination refers to when a language model generates confident-sounding but factually incorrect or fabricated information. This occurs because LLMs predict statistically likely text rather than retrieving verified facts. Mitigation strategies include RAG, grounding responses in source documents, structured output validation, and using temperature settings to reduce creative deviation.

Headless UI refers to component libraries that provide behavior, state management, and accessibility logic without any predefined styling or markup. Libraries like Radix Primitives, Headless UI by Tailwind Labs, and React Aria give developers full control over visual presentation while handling complex patterns like focus management, keyboard navigation, and ARIA attributes. This approach decouples functionality from design, making it ideal for custom design systems.

Hermes is an open-source JavaScript engine developed by Meta, optimized specifically for running React Native applications on mobile devices. It uses ahead-of-time (AOT) compilation to convert JavaScript into bytecode during the build process, resulting in faster app startup times, reduced memory usage, and smaller app sizes compared to JavaScriptCore. Hermes is now the default JavaScript engine for React Native and also supports iOS since React Native 0.70.

A Higher-Order Component (HOC) is an advanced React pattern where a function takes a component as input and returns a new enhanced component with additional props or behavior. Common use cases include adding authentication checks, analytics tracking, or data fetching logic to existing components. While HOCs were a primary code reuse pattern in class-based React, custom hooks have largely replaced them in modern functional component code due to their simpler composition model.

Hot reload is a development feature that injects updated code into a running application without restarting it or losing the current state. In Flutter, hot reload works by injecting updated Dart source code into the running Dart VM, typically completing in under a second. React Native offers a similar feature called Fast Refresh that preserves component state during edits. Both dramatically accelerate the development feedback loop compared to traditional compile-and-restart cycles.

Hydration is the process where a client-side JavaScript framework attaches event listeners and interactivity to server-rendered HTML markup. After the server sends pre-rendered HTML for fast initial display, the framework "hydrates" it by reconciling its virtual representation with the existing DOM and making it interactive. Hydration can be expensive on complex pages, which has led to innovations like partial hydration, progressive hydration, and React's selective hydration with Suspense.

Infinite scroll is a UX pattern where new content loads automatically as the user scrolls toward the bottom of the page, eliminating traditional pagination. It's commonly used in social media feeds and content discovery interfaces. While it increases engagement and feels seamless, it can hurt performance without virtualization and makes it difficult for users to reach footer content or bookmark specific positions.

Internationalization (i18n) is the process of designing software so it can be adapted to different languages, regions, and cultures without code changes. This involves externalizing strings, supporting right-to-left (RTL) layouts, handling date/number/currency formatting, and accommodating text expansion. Libraries like react-intl, next-intl, and i18next provide the infrastructure for managing translations and locale-aware formatting in JavaScript applications.

JSX (JavaScript XML) is a syntax extension for JavaScript used primarily in React that lets you write HTML-like markup directly within your JavaScript code. It gets transpiled by tools like Babel or SWC into regular `React.createElement()` calls before reaching the browser. JSX supports embedding dynamic expressions with curly braces, conditional rendering, and mapping over arrays, making it a powerful and intuitive way to describe UI structures declaratively.

A large language model (LLM) is a deep learning model trained on massive text datasets to understand and generate human-like text. LLMs like GPT, Claude, and LLaMA power chatbots, code assistants, and content generation tools. They work by predicting the next token in a sequence based on learned statistical patterns across billions of parameters.