add some comments

server.js

@@ -7,6 +7,8 @@ const resolve = file => path.resolve(__dirname, file)
 const express = require('express')
 const favicon = require('serve-favicon')
 const serialize = require('serialize-javascript')
+
+// https://github.com/vuejs/vue/blob/next/packages/vue-server-renderer/README.md#why-use-bundlerenderer
 const createBundleRenderer = require('vue-server-renderer').createBundleRenderer
 
 const app = express()

src/app.js

@@ -5,16 +5,25 @@ import router from './router'
 import { sync } from 'vuex-router-sync'
 import * as filters from './filters'
 
+// sync the router with the vuex store.
+// this registers `store.state.route`
 sync(store, router)
 
+// register global utility filters.
 Object.keys(filters).forEach(key => {
   Vue.filter(key, filters[key])
 })
 
+// create the app instance.
+// here we inject the router and store to all child components,
+// making them available everywhere as `this.$router` and `this.$store`.
 const app = new Vue({
   router,
   store,
-  ...App
+  ...App // Object spread copying everything from App.vue
 })
 
+// expose the app, the router and the store.
+// note we not mounting the app here, since bootstrapping will be
+// different depending on whether we are in browser or on the server.
 export { app, router, store }

src/client-entry.js

 require('es6-promise').polyfill()
 import { app, store } from './app'
 
-// prime the store with server-initialized state
+// prime the store with server-initialized state.
+// the state is determined during SSR and inlined in the page markup.
 store.replaceState(window.__INITIAL_STATE__)
 
+// actually mount to DOM
 app.$mount('#app')

src/server-entry.js

@@ -2,19 +2,33 @@ import { app, router, store } from './app'
 
 const isDev = process.env.NODE_ENV !== 'production'
 
+// This exported function will be called by `bundleRenderer`.
+// This is where we perform data-prefetching to determine the
+// state of our application before actually rendering it.
+// Since data fetching is async, this function is expected to
+// return a Promise that resolves to the app instance.
 export default context => {
   // set router's location
   router.push(context.url)
-  // call prefetch hooks on components matched by the route
+
   const s = isDev && Date.now()
+
+  // Call preFetch hooks on components matched by the route.
+  // A preFetch hook dispatches a store action and returns a Promise,
+  // which is resolved when the action is complete and store state has been
+  // updated.
   return Promise.all(router.getMatchedComponents().map(component => {
     if (component.preFetch) {
       return component.preFetch(store)
     }
   })).then(() => {
     isDev && console.log(`data pre-fetch: ${Date.now() - s}ms`)
-    // set initial store on context
-    // the request handler will inline the state in the HTML response.
+    // After all preFetch hooks are resolved, our store is now
+    // filled with the needed state to render the app.
+    // Expose the state on the render context, and let the request handler
+    // inline the state in the HTML response. This allows the client-side
+    // store to pick-up the server-side state without having to duplicate
+    // the initial data fetching on the client.
     context.initialState = store.state
     return app
   })

src/views/CreateListView.js

 import ItemList from '../components/ItemList.vue'
 
-// factory function for creating root-level list views
+// This is a factory function for dynamically creating root-level list views,
 // since they share most of the logic except for the type of items to display.
+// They are essentially higher order components wrapping ItemList.vue.
 export function createListView (type) {
   return {
     name: `${type}-stories-view`,