Hyperapp is a functional JavaScript framework for building hypertext applications. It centers on a state management library and a virtual DOM system that creates in-memory interface representations to apply efficient updates to the browser screen via diffing.
The framework avoids templates and JSX, instead utilizing function composition and dedicated tag wrappers to generate HTML structures and SVG elements. It implements a unidirectional data flow where a central state object is managed through transformation functions.
The system covers declarative UI rendering and functional web interfacing, bridging browser APIs and external events into the state loop. It includes mechanisms for asynchronous side effect execution, subscription-based event binding, and render performance optimizations that delay component updates until dependent data changes.