improve comments in server.js

server.js

@@ -9,31 +9,30 @@ const compression = require('compression')
 const serialize = require('serialize-javascript')
 const resolve = file => path.resolve(__dirname, file)
 
-// 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()
 
-// setup the server renderer, depending on dev/prod environment
-let html, renderer
+let indexHTML // generated by html-webpack-plugin
+let renderer  // created from the webpack-generated server bundle
 if (isProd) {
-  // create server renderer and index HTML from real fs
-  const bundlePath = resolve('./dist/server-bundle.js')
-  renderer = createRenderer(fs.readFileSync(bundlePath, 'utf-8'))
-  html = parseIndex(fs.readFileSync(resolve('./dist/index.html'), 'utf-8'))
+  // in production: create server renderer and index HTML from real fs
+  renderer = createRenderer(fs.readFileSync(resolve('./dist/server-bundle.js'), 'utf-8'))
+  indexHTML = parseIndex(fs.readFileSync(resolve('./dist/index.html'), 'utf-8'))
 } else {
+  // in development: setup the dev server with watch and hot-reload,
+  // and update renderer / index HTML on file change.
   require('./build/setup-dev-server')(app, {
     bundleUpdated: bundle => {
       renderer = createRenderer(bundle)
     },
     indexUpdated: index => {
-      html = parseIndex(index)
+      indexHTML = parseIndex(index)
     }
   })
 }
 
 function createRenderer (bundle) {
-  return createBundleRenderer(bundle, {
+  // https://github.com/vuejs/vue/blob/next/packages/vue-server-renderer/README.md#why-use-bundlerenderer
+  return require('vue-server-renderer').createBundleRenderer(bundle, {
     cache: require('lru-cache')({
       max: 1000,
       maxAge: 1000 * 60 * 15
@@ -65,7 +64,7 @@ app.get('*', (req, res) => {
   const renderStream = renderer.renderToStream(context)
 
   renderStream.once('data', () => {
-    res.write(html.head)
+    res.write(indexHTML.head)
   })
 
   renderStream.on('data', chunk => {
@@ -81,7 +80,7 @@ app.get('*', (req, res) => {
         }</script>`
       )
     }
-    res.end(html.tail)
+    res.end(indexHTML.tail)
     console.log(`whole request: ${Date.now() - s}ms`)
   })