Async

The Async module manages async data state and lightweight suspense reads. It depends on Core and Store, and does not operate on the DOM directly.

createResource

Manage async request state and return [resource, controls].

JavaScript
import { createResource } from 'vanilla-signal';const [user, controls] = createResource(  () => fetch('/api/user').then((res) => res.json()),  {    initialValue: null,  });user();user.loading();user.error();user.latest();controls.reload();controls.mutate((previous) => ({ ...previous, name: 'Ada' }));

With a source:

JavaScript
const [id, setId] = createSignal('1');const [user] = createResource(id, async (currentId) => {  const res = await fetch(`/api/users/${currentId}`);  return res.json();});

source can be valid values such as false, 0, or ''; only undefined means there is no source. Automatic loading triggered by source changes writes errors into state.error and does not create unhandled Promise rejections. When reload() / refetch() is called manually, the returned Promise still rejects the current request error to the caller.

Resource State

• data: current data.
• latest: most recent successful data.
• loading: whether a request is in progress.
• error: current error.
• isStale: whether existing data is refreshing.

Async Boundaries

• A new request aborts the previous request if it is still in progress.
• Success or failure from stale requests is ignored and will not overwrite current data or error state.
• Owner disposal aborts the current request, clears the loading timer, and ends loading/stale state.
• throwErrors: true only controls whether reading the resource throws state.error.

createSuspense

Catch a Promise thrown by a read function and return the fallback while pending.

JavaScript
const content = createSuspense(  () => readAsyncValue(),  () => 'loading...');

The current implementation is a lightweight runtime helper: it triggers recomputation after the Promise settles, but it does not pause the DOM render tree and does not provide a framework-level Suspense boundary, error boundary, or concurrency coordination.

Companion Tools

• vanilla-signal-query: browser-side server state management. It handles query state, cache, invalidation, and request lifecycle, without binding to DOM rendering or prescribing UI organization.
• vanilla-request: handles HTTP requests themselves: preparing requests, executing requests, parsing responses, running interceptors, request-level error recovery, and returning business data.