Serialization

IndexedDB can’t store arbitrary types (e.g. Date, custom classes). Use serialization to convert to/from storable shapes when writing and reading.

Example: custom class

class TimeStamp {
  date: Date
  constructor(initialValue?: string) {
    this.date = initialValue ? new Date(initialValue) : new Date()
  }

  toJSON() {
    return this.date.toISOString()
  }
}

type User = { id: string; name: string; createdAt: TimeStamp }
type UserDTO = { name: string }

export const users = Collection.create<User, UserDTO>()
  .withTransformers({
    create: (dto) => ({
      ...dto,
      id: crypto.randomUUID(),
      createdAt: new TimeStamp(),
    }),
  })
  .withSerialization({
    write: (user) => ({
      ...user,
      createdAt: user.createdAt.toJSON(),
    }),
    read: (serializedUser) => ({
      ...serializedUser,
      createdAt: new TimeStamp(serializedUser.createdAt),
    }),
  })

• write — Called before putting a record into IndexedDB. Return a plain, storable object.
• read — Called after reading from IndexedDB. Return the full, typed record (e.g. with new TimeStamp(...)).

Use this for Date, Map, Set, or any type that isn’t a plain JSON-like value.