@statesync/persistence

---

@statesync/persistence / migrateData

Function: migrateData()

function migrateData<T>(
   data, 
   fromVersion, 
handler): MigrationResult<T>;

Defined in: persistence/src/migration.ts:40

Migrate data from one schema version to another by applying migration functions sequentially.

Migrations are applied in order from fromVersion up to (but not including) handler.currentVersion. For example, migrating from v1 to v3 applies migrations[1] then migrations[2].

If fromVersion equals currentVersion, no migrations are applied and the data is optionally validated. If fromVersion is greater than currentVersion, the migration fails (data from a future version).

Type Parameters

Type Parameter	Description
T	The shape of the application state in the target (current) schema version.

Parameters

Parameter	Type	Description
data	unknown	The raw persisted data to migrate. Type is unknown because the source schema may differ from the current one.
fromVersion	number	The schema version of the stored data.
handler	MigrationHandler<T>	The migration handler containing the target version, migration functions, and optional validator.

Returns

MigrationResult<T>

A MigrationResult indicating success or failure, with the migrated data on success or an error on failure.

Example

const migration: MigrationHandler<AppState> = {
  currentVersion: 3,
  migrations: {
    1: (v1) => ({ ...v1, newField: 'default' }), // v1 -> v2
    2: (v2) => ({ ...v2, renamedField: v2.oldField }), // v2 -> v3
  },
};

const result = migrateData(oldData, 1, migration);
if (result.success) {
  console.log('Migrated to:', result.data);
}