svelte-cleanable-store

Custom Svelte store with built-in cleanup support on subscribe. Inspired by React's useEffect cleanup mechanism.

While the core functionality is simple and complete, this package is still pre-1.0 until I get feedback on the API shape. (e.g. Is cleanable a confusing name? Do we need a readable equivalent as well?)

Usage

const state = cleanable(0);

state.subscribe((value) => {
    console.log(`state = ${value}`);
    return () => console.log(`cleaning up ${value}...`);
});

Console output:

state = 0

// state++
cleaning up 0...
state = 1

// state = 5
cleaning up 1...
state = 5

Example

Closing a WebSocket connection

const path = cleanable("https://example.com/stream");
path.subscribe((value) => {
    const webSocket = new WebSocket(value);
    webSocket.onmessage = (event) => console.log(event);

    return () => webSocket.close();
});

But what about Svelte 5's `$effect`?

It's absolutely great! In fact, it inspired me to create this package.

However, Svelte 5 is still in beta now, and while there are many workarounds for Svelte 4, this package provides a clean, store-based solution that works with Svelte 4 (and 5), can be used anywhere (in plain .js/.ts files!), and is compatible with auto-subscriptions in .svelte files (with the $ prefix), all without feeling like a hack.