Function proxy

packages/svelte/src/internal/client/proxy.js:40–354

(value)

 * @returns {T}
 */
export function proxy(value) {
	// if non-proxyable, or is already a proxy, return `value`
	if (typeof value !== 'object' || value === null || STATE_SYMBOL in value) {
		return value;
	}

	const prototype = get_prototype_of(value);

	if (prototype !== object_prototype && prototype !== array_prototype) {
		return value;
	}

	/** @type {Map<any, Source<any>>} */
	var sources = new Map();
	var is_proxied_array = is_array(value);
	var version = source(0);

	var stack = DEV && tracing_mode_flag ? get_error('created at') : null;
	var parent_version = update_version;

	/**
	 * Executes the proxy in the context of the reaction it was originally created in, if any
	 * @template T
	 * @param {() => T} fn
	 */
	var with_parent = (fn) => {
		if (update_version === parent_version) {
			return fn();
		}

		// child source is being created after the initial proxy —
		// prevent it from being associated with the current reaction
		var reaction = active_reaction;
		var version = update_version;

		set_active_reaction(null);
		set_update_version(parent_version);

		var result = fn();

		set_active_reaction(reaction);
		set_update_version(version);

		return result;
	};

	if (is_proxied_array) {
		// We need to create the length source eagerly to ensure that
		// mutations to the array are properly synced with our proxy
		sources.set('length', source(/** @type {any[]} */ (value).length, stack));
		if (DEV) {
			value = /** @type {any} */ (inspectable_array(/** @type {any[]} */ (value)));
		}
	}

	/** Used in dev for $inspect.trace() */
	var path = '';
	let updating = false;