Dictionary

Tree shaking is a dead code elimination technique used by modern bundlers like Webpack, Rollup, and esbuild to remove unused exports from the final JavaScript bundle. It relies on the static structure of ES module `import`/`export` syntax to determine which code is actually referenced and safely discard the rest. For tree shaking to work effectively, libraries must use ESM format and avoid side effects in their module initialization, which is why the `sideEffects` field in `package.json` matters.

Turbo Modules are the next-generation native module system in React Native's New Architecture, replacing the traditional bridge-based modules. They use the JavaScript Interface (JSI) for direct, synchronous communication between JavaScript and native code, eliminating the serialization overhead of the old JSON bridge. Turbo Modules also support lazy loading — they're only initialized when first accessed rather than at app startup, which significantly improves launch performance.

Usability testing is a UX research method where real users attempt to complete specific tasks while observers note difficulties, confusion, and behavior patterns. It can be moderated (with a facilitator) or unmoderated (self-guided with recording), and conducted on prototypes or live products. Even testing with just 5 users typically uncovers the majority of usability issues, making it one of the highest-ROI activities in product development.

A vector database is a specialized database optimized for storing, indexing, and querying high-dimensional vector embeddings. They enable fast similarity search, which is critical for RAG systems, recommendation engines, and semantic search applications. Popular vector databases include Pinecone, Weaviate, Qdrant, and pgvector for PostgreSQL.

The View Transitions API is a browser-native way to create animated transitions between different DOM states or page navigations, previously only possible with complex JavaScript animation libraries. It captures a snapshot of the current state, applies the DOM update, then animates between the old and new snapshots using CSS. This API works for both single-page app state changes and multi-page navigations, enabling smooth page transitions with minimal code that feels native to the platform.

The Virtual DOM is a lightweight in-memory representation of the actual browser DOM that React uses to optimize UI updates. When state changes, React creates a new Virtual DOM tree, compares it with the previous one through a process called reconciliation, and calculates the minimal set of real DOM mutations needed. This batching and diffing approach avoids expensive direct DOM manipulation and was a key innovation that made React's declarative programming model performant.

A WebView is an embeddable browser component that renders web content (HTML, CSS, JavaScript) inside a native mobile application. It allows developers to reuse existing web code within a native app shell, commonly used for displaying rich content, integrating web-based features, or building hybrid apps. While convenient, WebView-heavy apps typically have worse performance and a less native feel compared to truly native or React Native/Flutter approaches.

In Flutter, the widget tree is the hierarchical structure of nested widgets that defines the entire UI of an application. Everything in Flutter is a widget — from layout structures like `Column` and `Row` to styling wrappers like `Padding` and `Theme` to interactive elements like `GestureDetector`. Flutter maintains three parallel trees (widget, element, and render object) that work together to efficiently rebuild only the parts of the UI that actually changed when state updates.

A wireframe is a low-fidelity visual representation of a user interface that outlines structure, layout, and content hierarchy without detailed styling or colors. Wireframes focus on what elements appear on a page and how they are arranged, serving as a blueprint before visual design begins. They help teams align on functionality and user flow early in the process, when changes are cheapest to make.