XState v6 alpha
Utilities
Work with actors, snapshots and state values.
XState v6 is in alpha
APIs and behavior may change before the stable release.
| Utility | Purpose |
|---|---|
waitFor(actor, predicate) | Wait for a matching snapshot. |
toPromise(actor) | Resolve with an actor's output. |
initialTransition(logic, input?) | Get [snapshot, actions] for the initial transition without starting an actor. |
transition(logic, snapshot, event) | Calculate [nextSnapshot, actions] for an event. |
mapState(...) | Map one state value to another value. |
SimulatedClock | Control time in tests. |
const finalSnapshot = await waitFor(actor, (snapshot) =>
snapshot.matches('complete')
);Use initialTransition(...) and transition(...) for pure calculations. They do not start actors or run effects; the returned actions describe the effects that an actor would execute. The older getInitialSnapshot(...) and getNextSnapshot(...) are deprecated aliases that return only the snapshot. Use SimulatedClock to test delays without waiting for real time.
For example, a route loader can calculate an initial view without starting a long-lived actor. A timeout test can advance a simulated clock to the retry state.
Utilities cheatsheet
await waitFor(actor, predicate);
await toPromise(actor);
const [initialSnapshot, initialActions] = initialTransition(logic, input);
const [nextSnapshot, actions] = transition(logic, snapshot, event);