Add some reducer utils

Author: goatslacker

foo.js

@@ -0,0 +1,24 @@
+import Alt from './'
+import { combine, reduceWith } from './utils/reducers'
+
+const alt = new Alt()
+
+const actions = alt.generateActions('fire', 'foo', 'bar')
+
+const store = alt.createStore({
+  state: 21,
+
+  displayName: 'ValueStore',
+
+  reduce: combine(
+    reduceWith([actions.fire], (state, payload) => {
+      return state + 1
+    })
+  )
+})
+
+store.listen(state => console.log('CHANGED', state))
+actions.fire()
+actions.foo()
+actions.bar()
+actions.fire()

src/utils/reducers.js

@@ -0,0 +1,42 @@
+import { assign } from './functions'
+
+function getId(x) {
+  return x.id || x
+}
+
+function shallowEqual(a, b) {
+  if (typeof a !== 'object' || typeof b !== 'object') return a === b
+  if (a === b) return true
+  if (!a || !b) return false
+  for (let k in a) {
+    if (a.hasOwnProperty(k) && (!b.hasOwnProperty(k) || a[k] !== b[k])) {
+      return false
+    }
+  }
+  for (let k in b) {
+    if (b.hasOwnProperty(k) && !a.hasOwnProperty(k)) {
+      return false
+    }
+  }
+  return true
+}
+
+export function combine(...restReducers) {
+  const reducers = assign.apply(null, [{}].concat(restReducers))
+  return function (state, payload) {
+    const newState = reducers.hasOwnProperty(payload.action)
+      ? reducers[payload.action](state, payload.data)
+      : state
+
+    if (shallowEqual(state, newState)) this.preventDefault()
+
+    return newState
+  }
+}
+
+export function reduceWith(actions, reduce) {
+  return actions.reduce((total, action) => {
+    total[getId(action)] = reduce
+    return total
+  }, {})
+}