Browser Extension (TypeScript, React, Webpack, Vitest) overview

A cross-browser extension built with TypeScript and React, packaging popup UIs, content scripts, background service workers, and options pages into a single distributable extension. Webpack bundles multiple entry points (background, content, popup) with shared code splitting and hot-reload support during development. React renders the popup and options interfaces, while content scripts inject UI overlays into target web pages using Shadow DOM for style isolation. TypeScript provides type-safe messaging between extension contexts (background, content, popup) through Chrome's runtime messaging API. Vitest tests business logic in isolation. The tradeoff is managing the complex lifecycle across multiple execution contexts and the divergent APIs between Chrome and Firefox, but extensions provide unique capabilities like page manipulation and cross-site data that web apps cannot access.