React Suspense
React-feature: deklarativ loading-state. <Suspense fallback={<Spinner />}><DataComponent /></Suspense>. Child kan "suspend" via throwa Promise — Suspense visar fallback tills resolved. Stabilt i React 18.
Use cases: lazy-loaded routes (React.lazy()), data fetching (with libraries like Relay, SWR, TanStack Query), Server Components streaming. Suspense-boundaries: nästade boundaries — outer-suspense visar overall, inner kan stream individual sections. Selective hydration: server streamar HTML, client hydrates components by priority (visible-first). Migration-friction: legacy data-fetching (useEffect + setState) inte-Suspense-aware → manuell wrapping. Konkurrent: Vue suspense, Solid resources, Svelte await-blocks — alla har equivalent-pattern.