1. make 3rd param of exec() optional 2. add types + jsdoc

src/router.d.ts

@@ -7,6 +7,27 @@ export function LocationProvider(props: {
 
 type NestedArray<T> = Array<T | NestedArray<T>>;
 
+/**
+ * Check if a URL path matches against a URL path pattern.
+ * 
+ * Warning: This is an internal API exported only for testing purpose. API could change in future.
+ * @param url - URL path (e.g. /user/12345)
+ * @param route - URL pattern (e.g. /user/:id)
+ */
+export function exec(url: string, route: string, matches: {
+	params: {
+		[param: string]: string;
+	};
+	rest?: string;
+	[props: string]: string;
+}): {
+	params: {
+		[param: string]: string;
+	},
+	rest?: string;
+	[propsOrParam: string]: string;
+}
+
 export function Router(props: {
 	onRouteChange?: (url: string) => void;
 	onLoadEnd?: (url: string) => void;

src/router.js

@@ -48,9 +48,10 @@ const UPDATE = (state, url) => {
 	return url;
 };
 
-export const exec = (url, route, matches) => {
+export const exec = (url, route, matches = {}) => {
 	url = url.split('/').filter(Boolean);
 	route = (route || '').split('/').filter(Boolean);
+	if (!matches.params) matches.params = {};
 	for (let i = 0, val, rest; i < Math.max(url.length, route.length); i++) {
 		let [, m, param, flag] = (route[i] || '').match(/^(:?)(.*?)([+*?]?)$/);
 		val = url[i];