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gustavomorinaga/overridable.store.ts

Created September 18, 2023 02:57
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Overridable Store for Svelte
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overridable.store.ts
import type { Updater, Writable } from 'svelte/store';
export type ChangeFn<T> = (args: { curr: T; next: T }) => T;
export const overridable = <T>(store: Writable<T>, onChange?: ChangeFn<T>) => {
const update = (updater: Updater<T>, sideEffect?: (newValue: T) => void) =>
store.update((curr) => {
const next = updater(curr);
let res: T = next;
if (onChange) res = onChange({ curr, next });
sideEffect?.(res);
return res;
});
const set: typeof store.set = (curr) => update(() => curr);
return { ...store, update, set };
};
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