make it better

src/reducers/index.js

@@ -0,0 +1,8 @@
+import { combineReducers } from 'redux'
+import product from './product_reducer'
+
+const compareApp = combineReducers({
+  product
+})
+
+export default compareApp

src/reducers/product_reducer.js

@@ -0,0 +1,26 @@
+import * as types from '../constants/types';
+
+const INITIAL_STATE = {
+  products: []
+};
+
+export default function (state = INITIAL_STATE, action) {
+  switch (action.type) {
+    case types.FETCH_PRODUCTS:
+      return {
+        ...state, products: action.payload.map(product =>
+          ({...product, compare: false})
+        )
+      };
+    case types.COMPARE_PRODUCT:
+      return {
+        ...state, products: state.products.map(product =>
+          product.id === action.product.id ?
+            ({...product, compare: !product.compare}) :
+            product
+        )
+      };
+    default:
+      return state;
+  }
+}