Improved looping; safely mutate listeners queue

.gitignore

@@ -7,3 +7,4 @@ package-lock.json
 /preact.js.map
 /react.js
 /react.js.map
+.vscode/

README.md

@@ -69,10 +69,10 @@ You can find the library on `window.unistore`.
 import createStore from 'unistore'
 import { Provider, connect } from 'unistore/preact'
 
-let store = createStore({ count: 0 })
+const store = createStore({ count: 0 })
 
 // If actions is a function, it gets passed the store:
-let actions = store => ({
+const actions = store => ({
   // Actions can just return a state update:
   increment(state) {
     return { count: state.count+1 }
@@ -90,7 +90,7 @@ let actions = store => ({
 
   // Async actions can be pure async/promise functions:
   async getStuff(state) {
-    let res = await fetch('/foo.json')
+    const res = await fetch('/foo.json')
     return { stuff: await res.json() }
   },
 
@@ -126,8 +126,8 @@ Make sure to have [Redux devtools extension](https://github.com/zalmoxisus/redux
 import createStore from 'unistore'
 import devtools    from 'unistore/devtools'
 
-let initialState = { count: 0 };
-let store = process.env.NODE_ENV === 'production' ?  createStore(initialState) : devtools(createStore(initialState));
+const initialState = { count: 0 };
+const store = process.env.NODE_ENV === 'production' ?  createStore(initialState) : devtools(createStore(initialState));
 
 // ...
 ```

package.json

@@ -10,12 +10,13 @@
   "scripts": {
     "build": "npm-run-all --silent -p build:main build:integrations build:combined -s size docs",
     "build:main": "microbundle",
-    "build:integrations": "microbundle src/integrations/*.js -o x.js -f cjs",
-    "build:combined": "microbundle src/combined/*.js -o full/x.js",
+    "build:integrations": "microbundle \"src/integrations/*.js\" -o x.js -f cjs",
+    "build:combined": "microbundle \"src/combined/*.js\" -o full/x.js",
     "size": "strip-json-comments --no-whitespace dist/unistore.js | gzip-size && bundlesize",
     "docs": "documentation readme unistore.js -q --section API && npm run -s fixreadme",
     "fixreadme": "node -e 'var fs=require(\"fs\");fs.writeFileSync(\"README.md\", fs.readFileSync(\"README.md\", \"utf8\").replace(/^-   /gm, \"- \"))'",
     "test": "eslint src && npm run build && jest",
+    "test:jest": "jest",
     "prepare": "npm t",
     "release": "npm t && git commit -am $npm_package_version && git tag $npm_package_version && git push && git push --tags && npm publish"
   },
@@ -28,15 +29,15 @@
   "bundlesize": [
     {
       "path": "full/preact.js",
-      "maxSize": "750b"
+      "maxSize": "730b"
     },
     {
       "path": "dist/unistore.js",
-      "maxSize": "400b"
+      "maxSize": "351b"
     },
     {
       "path": "preact.js",
-      "maxSize": "600b"
+      "maxSize": "523b"
     }
   ],
   "babel": {

src/index.js

@@ -11,26 +11,18 @@ import { assign } from './util';
  *    store.setState({ c: 'd' });   // logs { a: 'b', c: 'd' }
  */
 export default function createStore(state) {
-	let listeners = [];
+	const listeners = [];
 	state = state || {};
 
 	function unsubscribe(listener) {
-		let out = [];
-		for (let i=0; i<listeners.length; i++) {
-			if (listeners[i]===listener) {
-				listener = null;
-			}
-			else {
-				out.push(listeners[i]);
-			}
-		}
-		listeners = out;
+		const i = listeners.lastIndexOf(listener);
+		~i && listeners.splice(i, 1);
 	}
 
 	function setState(update, overwrite, action) {
 		state = overwrite ? update : assign(assign({}, state), update);
-		let currentListeners = listeners;
-		for (let i=0; i<currentListeners.length; i++) currentListeners[i](state, action);
+		let i = listeners.length;
+		while (i-- > 0) listeners[i](state, action);
 	}
 
 	/** An observable state container, returned from {@link createStore}
@@ -46,15 +38,15 @@ export default function createStore(state) {
 		 *  @returns {Function} boundAction()
 		 */
 		action(action) {
-			function apply(result) {
-				setState(result, false, action);
+			function apply(update) {
+				setState(update, false, action);
 			}
 
 			// Note: perf tests verifying this implementation: https://esbench.com/bench/5a295e6299634800a0349500
 			return function() {
-				let args = [state];
-				for (let i=0; i<arguments.length; i++) args.push(arguments[i]);
-				let ret = action.apply(this, args);
+				const args = [state];
+				for (let i = 0; i<arguments.length; i++) args.push(arguments[i]);
+				const ret = action.apply(this, args);
 				if (ret!=null) {
 					if (ret.then) ret.then(apply);
 					else apply(ret);

src/integrations/preact.js

@@ -21,8 +21,8 @@ export function connect(mapStateToProps, actions) {
 	return Child => {
 		function Wrapper(props, { store }) {
 			let state = mapStateToProps(store ? store.getState() : {}, props);
-			let boundActions = actions ? mapActions(actions, store) : { store };
-			let update = () => {
+			const boundActions = actions ? mapActions(actions, store) : { store };
+			const update = () => {
 				let mapped = mapStateToProps(store ? store.getState() : {}, this.props);
 				for (let i in mapped) if (mapped[i]!==state[i]) {
 					state = mapped;

src/integrations/react.js

@@ -27,9 +27,9 @@ export function connect(mapStateToProps, actions) {
 			Component.call(this, props, context);
 			let { store } = context;
 			let state = mapStateToProps(store ? store.getState() : {}, props);
-			let boundActions = actions ? mapActions(actions, store) : { store };
-			let update = () => {
-				let mapped = mapStateToProps(store ? store.getState() : {}, this.props);
+			const boundActions = actions ? mapActions(actions, store) : { store };
+			const update = () => {
+				const mapped = mapStateToProps(store ? store.getState() : {}, this.props);
 				for (let i in mapped) if (mapped[i]!==state[i]) {
 					state = mapped;
 					return this.forceUpdate();

src/util.js

@@ -1,10 +1,8 @@
 // Bind an object/factory of actions to the store and wrap them.
 export function mapActions(actions, store) {
 	if (typeof actions==='function') actions = actions(store);
-	let mapped = {};
-	for (let i in actions) {
-		mapped[i] = store.action(actions[i]);
-	}
+	const mapped = {};
+	for (let i in actions) mapped[i] = store.action(actions[i]);
 	return mapped;
 }
 
@@ -13,10 +11,9 @@ export function mapActions(actions, store) {
 export function select(properties) {
 	if (typeof properties==='string') properties = properties.split(/\s*,\s*/);
 	return state => {
-		let selected = {};
-		for (let i=0; i<properties.length; i++) {
-			selected[properties[i]] = state[properties[i]];
-		}
+		const selected = {};
+		let i = properties.length;
+		while (i-- > 0) selected[properties[i]] = state[properties[i]];
 		return selected;
 	};
 }

test/preact/unistore.test.js

@@ -51,6 +51,52 @@ describe('createStore()', () => {
 		expect(sub2).toBeCalledWith(store.getState(), action);
 	});
 
+	it('should invoke all subscriptions at time of setState, no matter unsubscriptions', () => {
+		let store = createStore();
+
+		let called = [];
+		let unsub2;
+
+		let sub1 = jest.fn(() => {
+			called.push(1);
+		});
+		let sub2 = jest.fn(() => {
+			called.push(2);
+			unsub2(); // unsubscribe during a listener callback
+		});
+		let sub3 = jest.fn(() => {
+			called.push(3);
+		});
+
+		let unsub1 = store.subscribe(sub1);
+		unsub2 = store.subscribe(sub2);
+		let unsub3 = store.subscribe(sub3);
+
+		store.setState({ a: 'a' });
+
+		expect(sub1).toHaveBeenCalledTimes(1);
+		expect(sub2).toHaveBeenCalledTimes(1);
+		expect(sub3).toHaveBeenCalledTimes(1);
+		expect(called.sort()).toEqual([1, 2, 3]);
+
+		store.setState({ a: 'b' });
+
+		expect(sub1).toHaveBeenCalledTimes(2);
+		expect(sub2).toHaveBeenCalledTimes(1);
+		expect(sub3).toHaveBeenCalledTimes(2);
+		expect(called.sort()).toEqual([1, 1, 2, 3, 3]);
+
+		unsub1();
+		unsub3();
+
+		store.setState({ a: 'c' });
+
+		expect(sub1).toHaveBeenCalledTimes(2);
+		expect(sub2).toHaveBeenCalledTimes(1);
+		expect(sub3).toHaveBeenCalledTimes(2);
+		expect(called.sort()).toEqual([1, 1, 2, 3, 3]);
+	});
+
 	it('should unsubscribe', () => {
 		let store = createStore();
 

test/react/unistore.test.js

@@ -51,6 +51,41 @@ describe('createStore()', () => {
 		expect(sub1).toHaveBeenLastCalledWith(store.getState(), undefined);
 		expect(sub2).toBeCalledWith(store.getState(), undefined);
 	});
+	it('should invoke all subscriptions at time of setState, no matter unsubscriptions', () => {
+		let store = createStore();
+		let called = [];
+		let unsub2;
+		let sub1 = jest.fn(() => {
+			called.push(1);
+		});
+		let sub2 = jest.fn(() => {
+			called.push(2);
+			unsub2(); // unsubscribe during a listener callback
+		});
+		let sub3 = jest.fn(() => {
+			called.push(3);
+		});
+		let unsub1 = store.subscribe(sub1);
+		unsub2 = store.subscribe(sub2);
+		let unsub3 = store.subscribe(sub3);
+		store.setState({ a: 'a' });
+		expect(sub1).toHaveBeenCalledTimes(1);
+		expect(sub2).toHaveBeenCalledTimes(1);
+		expect(sub3).toHaveBeenCalledTimes(1);
+		expect(called.sort()).toEqual([1, 2, 3]);
+		store.setState({ a: 'b' });
+		expect(sub1).toHaveBeenCalledTimes(2);
+		expect(sub2).toHaveBeenCalledTimes(1);
+		expect(sub3).toHaveBeenCalledTimes(2);
+		expect(called.sort()).toEqual([1, 1, 2, 3, 3]);
+		unsub1();
+		unsub3();
+		store.setState({ a: 'c' });
+		expect(sub1).toHaveBeenCalledTimes(2);
+		expect(sub2).toHaveBeenCalledTimes(1);
+		expect(sub3).toHaveBeenCalledTimes(2);
+		expect(called.sort()).toEqual([1, 1, 2, 3, 3]);
+	});
 	it('should unsubscribe', () => {
 		let store = createStore();
 		let sub1 = jest.fn();