Reducers

docs/api/Reflux.md

@@ -30,6 +30,28 @@ Creates an event emitting Data Store. It is mixed in with functions from the `Li
 
 @returns {Store} A data store instance
 
+## Reflux.createReducer(initialData)
+
+Creates a reducer, a data store that uses pure functions to mutate the data.
+
+@param {Mixed} initialData the initial data to seed the reducer
+
+@returns {Reducer} A reducer instance
+
+@example
+```javascript
+var addUser = Reflux.createAction({ sync: true });
+var reducer = Reflux.createReducer({ users: [] });
+
+reducer.on(addUser, function(data, newUser) {
+  data.users.push(newUser);
+  return data;
+})
+
+addUser("John Doe");
+reducer.peek(); // outputs { users: ["John Doe"] }
+```
+
 ## Reflux.joinTrailing(...publishers)
 
 Creates a static join for the given publishers. It emits when all the publishers have emitted at least once, and will emit with the data that was last emitted by each listenable.

package.json

@@ -15,7 +15,7 @@
     "benchmark": "node test/benchmarks",
     "watch:lint": "esw -w",
     "watch:test": "mocha -w -R min --compilers js:babel-core/register ./test",
-    "watch": "parallelshell 'npm run watch:test' 'npm run watch:lint'",
+    "watch": "parallelshell 'npm run watch:lint' 'npm run watch:test'",
     "prepublish": "npm run lint && npm run test:mocha && npm run clean && npm run compile",
     "precommit": "npm run lint && npm run test:mocha",
     "prepush": "npm run precommit"

src/createReducer.js

@@ -0,0 +1,27 @@
+import * as _ from "./utils";
+import PublisherMethods from "./PublisherMethods";
+
+export default function createReducer(initialData) {
+
+    var data = initialData;
+
+    function Reducer() {
+        this.emitter = new _.EventEmitter();
+        this.eventLabel = "reducer";
+    }
+
+    Reducer.prototype.on = function(publisher, reducerFn) {
+        publisher.listen(function() {
+            data = reducerFn.apply(this, [ data, ...arguments ]);
+            this.trigger(data);
+        }, this);
+    };
+
+    Reducer.prototype.peek = function() {
+        return data;
+    };
+
+    _.extend(Reducer.prototype, PublisherMethods);
+
+    return new Reducer();
+}

src/index.js

@@ -18,6 +18,7 @@ import * as _ from "./utils";
 const utils = _;
 import createAction from "./createAction";
 import createStore from "./createStore";
+import createReducer from "./createReducer";
 
 /**
  * Convenience function for creating a set of actions
@@ -83,6 +84,7 @@ export default {
     utils,
     createAction,
     createStore,
+    createReducer,
     createActions,
     setEventEmitter,
     nextTick,

test/creatingReducers.spec.js

@@ -0,0 +1,46 @@
+import chai, { assert } from 'chai';
+import asPromised from 'chai-as-promised';
+import Reflux from "../src";
+import sinon from "sinon";
+
+chai.use(asPromised);
+
+describe('with a reducer', function() {
+    describe('that has initial data', function() {
+        var reducer, initialData;
+
+        beforeEach(() => {
+            initialData = {
+                datum: 1337
+            };
+            reducer = Reflux.createReducer(initialData);
+        });
+
+        it('should be able to peek the data', function() {
+            assert.equal(initialData.datum, reducer.peek().datum);
+        });
+
+        describe('hooked to an action', function() {
+            var action, listener;
+
+            beforeEach(() => {
+                action = Reflux.createAction({sync: true});
+                listener = sinon.spy();
+                reducer.listen(listener);
+            });
+
+            it('should pass previous data as first argument', function() {
+                reducer.on(action, (a) => a);
+                action();
+                return assert.deepEqual(listener.args[0][0], initialData);
+            });
+
+            it('should pass arguments to the rest', function() {
+                reducer.on(action, (a, b, c) => { return {b: b, c: c}; });
+                action("dude", 1337);
+                return assert.deepEqual(reducer.peek(), {b: "dude", c: 1337});
+            });
+
+        });
+    });
+});