Core API

`createAsync(handler, options?)`

Creates an AsyncOperation. The handler receives an AsyncContext followed by the parameters passed to execute.

const operation = createAsync(async ({ signal, requestId }, id: string) => loadUser(id, signal), {
  concurrency: "latest",
  abortable: true,
});

Handler context

Field	Type	Description
`signal`	`AbortSignal \| null`	Present when `abortable` is enabled
`requestId`	`number`	Monotonically increasing operation-local request identifier

Options

Option	Default	Description
`initialData`	`null`	Data used for the initial and reset snapshots
`dataOnError`	Preserve data	Produces replacement data after a rejection
`concurrency`	`"all"`	Selects all-request or latest-request state updates
`abortable`	`false`	Creates an `AbortController` for every execution
`isEqual`	All fields	Determines whether a new snapshot is ignored
`onSuccess`	—	Runs after an accepted successful state update
`onError`	—	Runs after an accepted error state update

Operation

Method	Description
`getSnapshot()`	Returns the current frozen snapshot
`subscribe(listener)`	Subscribes to accepted snapshot changes and returns an unsubscribe function
`execute(...params)`	Starts the handler and returns its promise
`abort()`	Aborts controllers, invalidates active work, and returns to idle
`reset()`	Invalidates active work and restores initial state

Error behavior

execute() does not consume errors. It updates the snapshot and invokes onError, then rejects with the original error so the caller decides how to handle it.

try {
  await operation.execute();
} catch (error) {
  // Handle the same rejection stored in operation.getSnapshot().error.
}

Svelte

React API