add combineStores function

store.js

@@ -78,6 +78,7 @@ assign(Store.prototype, {
 		}
 
 		Object.defineProperty(this._proto, key, {
+			enumerable: true,
 			get: function() {
 				if (store._dirty[key]) {
 					var values = deps.map(function(dep) {
@@ -162,4 +163,24 @@ assign(Store.prototype, {
 	}
 });
 
-export default Store;
+function combineStores(store, children) {
+	var updates = {};
+
+	for (const key in children) {
+		const child = children[key];
+		updates[key] = child.get();
+
+		child.onchange(state => {
+			var update = {};
+			update[key] = state;
+			store.set(update);
+		});
+	}
+
+	console.log('updates', updates);
+
+	store.set(updates);
+	return store;
+}
+
+export { Store, combineStores };

test/runtime/samples/store-binding/_config.js

@@ -1,4 +1,4 @@
-import Store from '../../../../store.js';
+import { Store } from '../../../../store.js';
 
 const store = new Store({
 	name: 'world'

test/runtime/samples/store-computed/_config.js

@@ -1,4 +1,4 @@
-import Store from '../../../../store.js';
+import { Store } from '../../../../store.js';
 
 class MyStore extends Store {
 	setFilter(filter) {

test/runtime/samples/store-event/_config.js

@@ -1,4 +1,4 @@
-import Store from '../../../../store.js';
+import { Store } from '../../../../store.js';
 
 class MyStore extends Store {
 	setName(name) {

test/runtime/samples/store/_config.js

@@ -1,4 +1,4 @@
-import Store from '../../../../store.js';
+import { Store } from '../../../../store.js';
 
 const store = new Store({
 	name: 'world'

test/store/index.js

@@ -1,5 +1,5 @@
 import assert from 'assert';
-import Store from '../../store.js';
+import { Store, combineStores } from '../../store.js';
 
 describe('store', () => {
 	describe('get', () => {
@@ -143,4 +143,40 @@ describe('store', () => {
 			}, /'bar' is a read-only property/);
 		});
 	});
+
+	describe('combineStores', () => {
+		it('merges stores', () => {
+			const a = new Store({
+				x: 1,
+				y: 2
+			});
+
+			a.compute('z', ['x', 'y'], (x, y) => x + y);
+
+			const b = new Store({
+				x: 3,
+				y: 4
+			});
+
+			b.compute('z', ['x', 'y'], (x, y) => x + y);
+
+			const c = combineStores(new Store(), { a, b });
+
+			c.compute('total', ['a', 'b'], (a, b) => a.z + b.z);
+
+			assert.deepEqual(c.get(), {
+				a: {
+					x: 1,
+					y: 2,
+					z: 3
+				},
+				b: {
+					x: 3,
+					y: 4,
+					z: 7
+				},
+				total: 10
+			});
+		});
+	});
 });