Mutations

README.md

@@ -147,6 +147,7 @@ Creates a new store, which is a tiny evented state container.
 **Parameters**
 
 - `state` **[Object](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Object)** Optional initial state (optional, default `{}`)
+- `mutations`   (optional, default `false`)
 
 **Examples**
 

package.json

@@ -28,11 +28,11 @@
   "bundlesize": [
     {
       "path": "full/preact.js",
-      "maxSize": "760b"
+      "maxSize": "819b"
     },
     {
       "path": "dist/unistore.js",
-      "maxSize": "400b"
+      "maxSize": "417b"
     },
     {
       "path": "preact.js",

src/index.js

@@ -11,7 +11,7 @@ import { assign } from './util';
  * store.setState({ a: 'b' });   // logs { a: 'b' }
  * store.setState({ c: 'd' });   // logs { a: 'b', c: 'd' }
  */
-export default function createStore(state) {
+export default function createStore(state, mutations=false) {
 	let listeners = [];
 	state = state || {};
 
@@ -34,6 +34,11 @@ export default function createStore(state) {
 		for (let i=0; i<currentListeners.length; i++) currentListeners[i](state, action);
 	}
 
+	function mutate(action, overwrite) {
+		const key = Object.keys(action)[0];
+		setState(mutations[key](state, action[key]), overwrite, action);
+	}
+
 	/**
 	 * An observable state container, returned from {@link createStore}
 	 * @name store
@@ -50,7 +55,10 @@ export default function createStore(state) {
 		 */
 		action(action) {
 			function apply(result) {
-				setState(result, false, action);
+				if (!mutations)
+					setState(result, false, action);
+				else
+					mutate(result, false);
 			}
 
 			// Note: perf tests verifying this implementation: https://esbench.com/bench/5a295e6299634800a0349500
@@ -72,6 +80,8 @@ export default function createStore(state) {
 		 */
 		setState,
 
+		mutate,
+
 		/**
 		 * Register a listener function to be called whenever state is changed. Returns an `unsubscribe()` function.
 		 * @param {Function} listener	A function to call when state changes. Gets passed the new state.

test/unistore.test.js

@@ -47,6 +47,18 @@ describe('createStore()', () => {
 		expect(sub2).toBeCalledWith(store.getState(), action);
 	});
 
+	it('should invoke subscriptions using mutations', () => {
+		let store = createStore({ foo: 0 }, {
+			setFoo: (state, {v}) => ({ foo: v }),
+		})
+
+		let sub = jest.fn();
+		let rval = store.subscribe(sub);
+
+		store.mutate({ setFoo: { v: 1 } });
+		expect(sub).toBeCalledWith(store.getState(), { setFoo: { v: 1 } })
+	});
+
 	it('should unsubscribe', () => {
 		let store = createStore();
 
@@ -93,5 +105,14 @@ describe('createStore()', () => {
 		expect(sub1).not.toBeCalled();
 		expect(sub2).not.toBeCalled();
 		expect(sub3).not.toBeCalled();
-	});
+	 });
+
+	 it('should allow mutations', () => {
+		let store = createStore({ foo: 0 }, {
+			setFoo: (state, {v}) => ({ foo: v }),
+		})
+
+		store.mutate({ setFoo: { v: 1 } })
+		expect(store.getState()).toMatchObject({ foo: 1 })
+     });
 });