Function user_effect

packages/svelte/src/internal/client/reactivity/effects.js:203–229

(fn)

 * @param {() => void | (() => void)} fn
 */
export function user_effect(fn) {
	validate_effect('$effect');

	if (DEV) {
		define_property(fn, 'name', {
			value: '$effect'
		});
	}

	// Non-nested `$effect(...)` in a component should be deferred
	// until the component is mounted
	var flags = /** @type {Effect} */ (active_effect).f;
	var defer =
		!active_reaction &&
		(flags & BRANCH_EFFECT) !== 0 &&
		component_context !== null &&
		!component_context.i;

	if (defer) {
		// Top-level `$effect(...)` in an unmounted component — defer until mount
		var context = /** @type {ComponentContext} */ (component_context);
		(context.e ??= []).push(fn);
	} else {
		// Everything else — create immediately
		return create_user_effect(fn);
	}
}

/**
 * @param {() => void | (() => void)} fn