react‑side‑effect is a tiny higher‑order component library that lets you declaratively map the props of any number of mounted React components to a single global side effect (e.g., updating document.title, body styles, dispatching Flux actions). It aggregates props from the whole component tree, works on both client and server (with peek/rewind for SSR), and is aimed at React developers who need a clean, testable way to synchronize React state with external side effects.