@sv-use/core/dist/watch/index.svelte.js

A collection of Svelte 5 utilities.

/**
 * Copied and adapted from Svecosystem Runed, all credit goes to them.
 * https://github.com/svecosystem/runed/blob/main/packages/runed/src/lib/utilities/watch/watch.svelte.ts
 */
import { untrack } from 'svelte';
import { normalizeValue } from '../__internal__/utils.svelte.js';
/**
 * Triggers a callback when a dependency changes.
 * @param deps The dependencies to watch.
 * @param fn The callback to trigger when a dependency changes.
 * @param options Additional options to customize the behavior.
 * @note `watch` is a `$effect` but supplies the previous value(s) as the second argument.
 * @see https://svelte-librarian.github.io/sv-use/docs/core/watch
 */
export function watch(deps, fn, options = {}) {
    const { runOnMounted = true } = options;
    let active = runOnMounted;
    let previousValues = undefined;
    $effect(() => {
        const values = $state.snapshot(Array.isArray(deps) ? deps.map(normalizeValue) : deps());
        if (!active) {
            active = true;
            previousValues = values;
            return;
        }
        // @ts-expect-error Should fix type error on `previousValues`
        const cleanup = untrack(() => fn(values, previousValues));
        previousValues = values;
        return cleanup;
    });
}