@svelte-suspense/signal-store

This implements a signal based Svelte store. This allows writing code similar to Svelte 5's $derived.by even in Svelte 4 and will ease transitioning code from stores in Svelte 4 to $state in Svelte 5.

Installation

npm install --save @svelte-suspense/signal-store

API

ReadableSignalStore

import type { Readable } from 'svelte/store'

type ReadableSignalStore<T> = Readable<T> & {
	readonly value: T
}

WritableSignalStore

import type { Writable } from 'svelte/store'

type WritableSignalStore<T> = Writable<T> & {
	value: T
}

readable

import { readable } from '@svelte-drama/signal-store

const time = readable(new Date(), (set) => {
  // This function is not run until time has subscribers
  // or if `.value` is accessed inside of `computed`
	set(new Date());

	const interval = setInterval(() => {
		set(new Date());
	}, 1000);

	return () => clearInterval(interval);
})

// Reading the value is not reactive unless inside `computed`
console.log(time.value)

readable takes the same arguments as Svelte's readable. Additionally, the current value is available through .value.

writable

import { writable } from '@svelte-drama/signal-store

writable takes the same arguments as Svelte's writable. Additionally, the current value is available through .value.

computed

function computed<T>(fn: () => T): ReadableSignalStore<T>

import { computed, writable } from '@svelte-drama/signal-store

const count = writable(1)
const doubled = computed(() => {
  return count * 2
})
console.log(doubled.value) // 2

count.set(8)
console.log(doubled.value) // 16