precompile

config/application.rb

@@ -10,6 +10,7 @@ module SampleApp
   class Application < Rails::Application
     # Initialize configuration defaults for originally generated Rails version.
     config.load_defaults 6.1
+    config.assets.initialize_on_precompile = false
 
     # Configuration for the application, engines, and railties goes here.
     #

package.json

@@ -18,5 +18,13 @@
   "version": "0.1.0",
   "devDependencies": {
     "webpack-dev-server": "^3.11.2"
+  },
+  "scripts": {
+    "dev": "react-scripts start",
+    "start": "serve -s build",
+    "build": "react-scripts build",
+    "test": "react-scripts test --env=jsdom",
+    "eject": "react-scripts eject",
+    "heroku-postbuild": "npm run build"
   }
 }