@melt-ui/svelte/dist/internal/helpers/store/effect.js


import { derived } from 'svelte/store';
import { noop } from '../index.js';
import { safeOnDestroy } from '../lifecycle.js';
/**
 * A utility function that creates an effect from a set of stores and a function.
 * The effect is automatically cleaned up when the component is destroyed.
 *
 * @template S - The type of the stores object
 * @param stores - The stores object to derive from
 * @param fn - The function to run when the stores change
 * @param opts {@link EffectOptions}
 * @returns A function that can be used to unsubscribe the effect
 */
export function effect(stores, fn, opts = {}) {
    const { skipFirstRun } = opts;
    let isFirstRun = true;
    let cb = undefined;
    // Create a derived store that contains the stores object and an onUnsubscribe function
    const destroy = derived(stores, (stores) => {
        cb?.();
        if (isFirstRun && skipFirstRun) {
            isFirstRun = false;
        }
        else {
            cb = fn(stores);
        }
    }).subscribe(noop);
    const unsub = () => {
        destroy();
        cb?.();
    };
    // Automatically unsubscribe the effect when the component is destroyed
    safeOnDestroy(unsub);
    return unsub;
}