Synced Store

Utility for creating Svelte stores that automatically persist to and restore from storage providers.

Functions

synced(config)

Creates a writable store that synchronizes with a storage provider using JSON serialization.

Parameters:

• config - Configuration object containing:
  • key - Storage key to store the value under
  • storage - Storage provider implementing the StorageProvider interface
  • defaultValue - Default value if nothing exists in storage

Returns: Writable Svelte store that persists changes to storage

The store automatically:

• Loads initial value from storage on creation
• Saves any changes back to storage
• Falls back to defaultValue if storage is empty or invalid

Storage Provider Interface

interface StorageProvider {
  get: (key: string) => Promise<any>
  set: (key: string, value: any) => Promise<void>
}

Example

import {synced, localStorageProvider} from "@welshman/store"

// Create a store that persists user preferences using localStorage
const userPreferences = synced({
  key: "user-prefs",
  storage: localStorageProvider,
  defaultValue: {
    theme: "dark",
    notifications: true,
    language: "en"
  }
})

// Use like any writable store
userPreferences.subscribe(prefs => {
  console.log("Preferences:", prefs)
})

// Update the store - automatically saves to storage
userPreferences.update(prefs => ({
  ...prefs,
  theme: "light"
}))