A JavaScript library for building user interfaces, developed by Meta. It lets you compose UIs from reusable components, manage state declaratively, and update the DOM efficiently through a virtual representation. React is the foundation of countless web applications and the entry point to the modern front-end ecosystem.
Incremental Static Regeneration is the bridge between the two extremes of web rendering. Pure static generation produces fast pages but freezes content at build time. Pure server-side rendering produces fresh content but pays a computation cost on every request. ISR takes a third path: it serves static HTML from a cache, and when that cache…
Partial Prerendering is the rendering model that dissolves the boundary between static and dynamic. In the Next.js App Router, a route is no longer forced to choose one or the other: the server can ship a fully static shell immediately, leaving holes for the personalized or request-dependent sections, and stream those holes in as they…
A Server Function is an async function marked with “use server” that a Client Component can call over the network. The client never receives the function’s code; it receives a reference, and when it invokes that reference, React sends a request to the server, executes the function there, and serializes the result back . The…
The Server-Client boundary in React Server Components is one-directional by design: the server sends serialized data to the client, and the client cannot reach back into the server’s memory. But the boundary is also a leak surface. A Server Component that fetches a user record and passes it to a Client Component sends every field…
Internationalization in React is not a single problem wearing three masks. It is three problems that share a name: translating text, formatting locale-sensitive data like dates and currencies, and structuring the application so the right language reaches the right user. The first two are largely solved by the platform—the browser’s Intl object handles formatting natively—while…
A React component that manages complex interaction logic with useState and useEffect is, in the formal sense, an infinite state machine. Any combination of boolean flags and nullable values can occur, including combinations that should be impossible. XState replaces that open-ended model with a finite state machine: a declared set of states, a declared set…
A WebSocket is a persistent, bidirectional connection between the browser and a server. Unlike HTTP, where every request opens a new connection and waits for a response, a WebSocket stays open and allows either side to send data at any time. React does not have a built-in WebSocket abstraction, and the browser’s WebSocket API is…
An offline-first application assumes the network is unreliable and designs for that assumption from the start. It loads from a local cache, writes to local storage immediately, and synchronizes with the server when connectivity returns. React does not provide this behavior natively; the browser does, through two APIs that work outside the component tree: the…
A React monorepo is not a repository with multiple package.json files. It is a repository where the dependency graph between packages is known, where a change to a shared UI component triggers only the builds and tests that depend on it, and where the CI pipeline finishes in seconds rather than minutes because the cache…
A reusable component library is not a folder of .tsx files copied between projects. It is a package with a stable public API, a build that produces both ESM and CommonJS output, a set of peer dependencies that prevents duplicate React instances, and a development environment where every component can be rendered in isolation. The…