SolidJS 2.0 ships with a native async-data model that lets a component treat a promise like any other reactive value, and it does so without the cascade of re-renders that React developers see with Suspense and hooks. The change matters because it keeps UI on screen while data refreshes, cuts boilerplate, and offers a concrete path for React teams to move their data-fetching code over to Solid.

Why Solid’s async model feels different

In React, a component that needs data usually calls a hook (often a custom one) that returns a promise-like object, then wraps the UI in <Suspense> to show a fallback while the promise resolves. Every time the promise settles, React schedules a re-render; if the same component later refetches, the fallback can flash over content that is already visible.

Solid flips the script. A promise is simply a value that the reactive graph watches. When a computation reads that value, the graph pauses that read until the promise resolves, but the rest of the UI stays rendered. The first time a component mounts, a <Loading> boundary can display a fallback; after that, a refetch leaves the existing DOM untouched until the new data arrives. No explicit “await” inside the component, no createResource, no manual state toggles.

The core primitives

  • <Loading> boundary – Replaces React’s <Suspense>. It shows a fallback only on the initial load. After the first paint, a pending read does not replace the UI; the old content remains until the fresh value resolves. Pass an on prop to force a spinner on a specific refetch.
  • <Reveal> component – Controls how multiple <Loading> boundaries appear together. Choose:
    • Sequential: boundaries reveal one after another in DOM order.
    • Together: all reveal at once when every piece of data is ready.
    • Natural: each reveals as soon as its own data lands.
  • isPending signal – Returns true while a particular read is in flight. Use it to overlay a thin loading bar or subtle animation while the main content stays visible, giving you “stale-while-revalidate” for free.
  • action generator – Replaces React’s mutable-state updates. An action(function*…) can optimistically update the UI, yield to wait for a server response, then reconcile the result when the promise resolves. The UI feels instant, and the reconciliation step is baked into the primitive.

How the pieces map to React concepts

Feature React approach Solid 2.0 approach
Data fetching use() (experimental) or third-party hooks; result wrapped in <Suspense> createMemo (or similar) that returns a promise; read directly in JSX
Loading UI <Suspense> may re-trigger fallback on every refetch <Loading> only on first load; refetch keeps old UI
Refreshing useTransition to defer UI updates isPending signals pending reads without UI swap
Mutations useState/useReducer + async calls, often wrapped in custom actions action(function*…) with built-in optimistic handling

The practical upshot is that Solid builds what React treats as separate hooks into the core reactivity engine.

A step-by-step migration guide

  1. डेटा स्रोत ओळखा – React मध्ये तुमच्याकडे बहुधा const data = useMyFetch(url) असेल. Solid मध्ये त्याऐवजी promise रिटर्न करणारा memo वापरा: const data = createMemo(() => fetch(url).then(r => r.json())).
  2. टॉप-लेव्हल कंपोनंटला वेढून घ्या (Wrap करा) – जर promise रिझॉल्व्ह होण्यापूर्वी कंपोनंट रेंडर होत असेल, तर त्याला `<Loading fallback={}>…</