svelte-settings/dist/utils/stores.js

> [!WARNING] > This project is a work in progress. Do not use it in any of your projects yet.

import { deepEqual } from '../deep.js';
import { readable, writable } from 'svelte/store';
import { browser } from '$app/environment';
/**
 * Creates a subscription to a nested part of the store according to the selector.
 * The subscription only fires when this part changes, and ignores changes to the rest of the store.
 *
 * @param selector A function which returns the part of the store to subscribe to. Being a callback allows for type support.
 * @param isEqual A callback which allows for overriding the equality checks, e.g. for objects.
 */
export function select(store, selector, isEqual = deepEqual) {
    return {
        subscribe(run) {
            let prev;
            return store.subscribe((value) => {
                const next = selector(value);
                console.debug('store select compare', prev, next, isEqual(prev, next));
                if (prev === undefined || !isEqual(prev, next)) {
                    prev = structuredClone(next);
                    run(next);
                }
            });
        },
    };
}
export function isStore(value) {
    return (typeof value === 'object' &&
        value !== null &&
        'subscribe' in value &&
        typeof value.subscribe === 'function');
}
/**
 * A helper to convert either a value, a value callback or a Readable to a Readable.
 */
export function toReadable(value) {
    if (isStore(value)) {
        return value;
    }
    if (typeof value === 'function') {
        const fn = value;
        return readable(undefined, (set) => {
            let cancelled = false;
            fn().then((res) => {
                if (!cancelled)
                    set(res);
            });
            return () => {
                cancelled = true;
            };
        });
    }
    return readable(value);
}