Add comments about __SERVER_DATA__

scripts/build.js

@@ -3,6 +3,8 @@
 // Do this as the first thing so that any code reading it knows the right env.
 process.env.NODE_ENV = 'production';
 
+// Use dynamic server data in production by inserting a token that will be
+// replaced when the HTML page is served.
 process.env.REACT_APP_SERVER_DATA = '__SERVER_DATA__';
 
 // Load environment variables from .env file. Suppress warnings using silent

scripts/start.js

@@ -2,6 +2,7 @@
 
 process.env.NODE_ENV = 'development';
 
+// Use static server data in development.
 process.env.REACT_APP_SERVER_DATA = JSON.stringify(require('../server/dev-data'))
 
 // Load environment variables from .env file. Suppress warnings using silent

server/index.js

@@ -19,6 +19,8 @@ const sendHomePage = (publicDir) => {
       } else {
         res.set('Cache-Control', 'public, max-age=60')
         res.send(
+          // Replace the __SERVER_DATA__ token that was added to the
+          // HTML file in the build process (see scripts/build.js).
           html.replace('__SERVER_DATA__', JSON.stringify({
             cloudflareStats: stats
           }))