@madkarma/svelte-storable

A lightweight Svelte store that automatically persists its value to localStorage. Perfect for maintaining state across browser sessions with minimal setup.

Features

• 🔄 Auto-persistence: Automatically syncs store values with localStorage
• 🎯 Type-safe: Full TypeScript support with generic types
• 🛠️ Customizable: Custom serialization/deserialization functions
• 🧹 Clean API: Simple, intuitive interface extending Svelte's writable store

📦 Installation

npm install @madkarma/svelte-storable

bun add @madkarma/svelte-storable

pnpm add @madkarma/svelte-storable

yarn add @madkarma/svelte-storable

🚀 Basic Usage

import storable from '@madkarma/svelte-storable';

// Create a persisted store
const count = storable('count', 0);

// Use it like a regular Svelte store
count.set(5);
count.update((n) => n + 1);

// The value is automatically saved to localStorage
// and restored on page reload

In your Svelte component:

<script>
	import storable from '@madkarma/svelte-storable';

	const count = storable('count', 0);
</script>

<h1>Count: {$count}</h1>
<button on:click={() => count.update((n) => n + 1)}> Increment </button>

📖 API

storable(key, initial, options?)

Creates a persistent Svelte store.

Parameters

• key (string): The localStorage key to store the value under
• initial (T): The initial value of the store
• options (optional): Configuration object
  • serialize ((value: T) => string): Custom serialization function (defaults to JSON.stringify)
  • deserialize ((value: string) => T): Custom deserialization function (defaults to JSON.parse)
  • saveInitial (boolean): Whether to save the initial value to localStorage if no stored value exists (defaults to true)

Returns

A store object with the following methods:

• subscribe(callback): Subscribe to store changes (standard Svelte store method)
• set(value): Set a new value
• update(updater): Update the value using an updater function
• reset(): Reset the store to its initial value
• remove(reset?): Remove the value from localStorage
  • reset (boolean): Whether to also reset the store value to initial (defaults to true)

💡 Examples

Basic Counter

import storable from '@madkarma/svelte-storable';

const count = storable('count', 0);

count.update((n) => n + 1); // Automatically saved to localStorage

Custom Serialization (Date Example)

const lastVisit = storable('lastVisit', new Date(), {
	serialize: (date) => date.toISOString(),
	deserialize: (str) => new Date(str)
});

Don't Save Initial Value

Useful when you only want to persist values that the user has explicitly set:

const preferences = storable('prefs', { theme: 'dark' }, { saveInitial: false });

// Initial value won't be saved to localStorage until user changes it

User Preferences

type UserPreferences = {
	theme: 'light' | 'dark';
	language: string;
	notifications: boolean;
};

const preferences = storable<UserPreferences>('user-prefs', {
	theme: 'dark',
	language: 'en',
	notifications: true
});

Reset to Initial Value

const settings = storable('settings', { volume: 50 });

settings.set({ volume: 80 });
settings.reset(); // Back to { volume: 50 }

Remove from Storage

const token = storable('auth-token', null);

// Remove from localStorage and reset to initial value
token.remove();

// Remove from localStorage but keep current value in store
token.remove(false);

📘 TypeScript

Full TypeScript support is included. The store is generic and will infer types from your initial value:

// Type is inferred as Writable<number>
const count = storable('count', 0);

// Type is inferred as Writable<string>
const name = storable('name', 'John');

// Explicit type annotation
const data = storable<{ id: number; name: string }>('data', {
	id: 1,
	name: 'Example'
});

✅ Requirements

• Svelte 5.0.0 or higher

📄 License

MIT

🤝 Contributing

Contributions are welcome! Please feel free to submit a Pull Request.