Upgrade core-js

app/javascript/shared/polyfills.js

@@ -1,9 +1,10 @@
 // Include runtime-polyfills for older browsers.
 // Due to babel.config.js's 'useBuiltIns', only polyfills actually
 // required by the browsers we support will be included.
-import '@babel/polyfill';
+import 'core-js/stable';
+import 'regenerator-runtime/runtime';
 import 'dom4';
+import 'intersection-observer';
+
 import './polyfills/insertAdjacentElement';
 import './polyfills/dataset';
-
-import('intersection-observer');

babel.config.js

@@ -29,8 +29,8 @@ module.exports = function(api) {
         require('@babel/preset-env').default,
         {
           forceAllTransforms: true,
-          useBuiltIns: 'entry',
-          corejs: 2,
+          useBuiltIns: 'usage',
+          corejs: 3,
           modules: false,
           exclude: ['transform-typeof-symbol']
         }

config/environments/development.rb

@@ -39,6 +39,9 @@ Rails.application.configure do
   # yet still be able to expire them through the digest params.
   config.assets.digest = true
 
+  # Suppress logger output for asset requests.
+  config.assets.quiet = true
+
   # Adds additional error checking when serving assets at runtime.
   # Checks for improperly declared sprockets dependencies.
   # Raises helpful error messages.

package.json

@@ -13,7 +13,7 @@
     "babel-plugin-macros": "^2.8.0",
     "babel-plugin-transform-react-remove-prop-types": "^0.4.24",
     "chartkick": "^3.2.0",
-    "core-js": "^2.0.0",
+    "core-js": "^3.6.4",
     "debounce": "^1.2.0",
     "dom4": "^2.1.5",
     "email-butler": "^1.0.13",

yarn.lock

@@ -2572,16 +2572,16 @@ core-js-compat@^3.6.0:
     browserslist "^4.8.3"
     semver "7.0.0"
 
-core-js@^2.0.0:
-  version "2.6.9"
-  resolved "https://registry.yarnpkg.com/core-js/-/core-js-2.6.9.tgz#6b4b214620c834152e179323727fc19741b084f2"
-  integrity sha512-HOpZf6eXmnl7la+cUdMnLvUxKNqLUzJvgIziQ0DiF3JwSImNphIqdGqzj6hIKyX04MmV0poclQ7+wjWvxQyR2A==
-
 core-js@^3.4.0:
   version "3.6.2"
   resolved "https://registry.yarnpkg.com/core-js/-/core-js-3.6.2.tgz#2799ea1a59050f0acf50dfe89b916d6503b16caa"
   integrity sha512-hIE5dXkRzRvnZ5vhkRfQxUvDxQZmD9oueA08jDYRBKJHx+VIl/Pne/e0A4x9LObEEthC/TqiZybUoNM4tRgnKg==
 
+core-js@^3.6.4:
+  version "3.6.4"
+  resolved "https://registry.yarnpkg.com/core-js/-/core-js-3.6.4.tgz#440a83536b458114b9cb2ac1580ba377dc470647"
+  integrity sha512-4paDGScNgZP2IXXilaffL9X7968RuvwlkK3xWtZRVqgd8SYNiVKRJvkFd1aqqEuPfN7E68ZHEp9hDj6lHj4Hyw==
+
 core-util-is@1.0.2, core-util-is@~1.0.0:
   version "1.0.2"
   resolved "https://registry.yarnpkg.com/core-util-is/-/core-util-is-1.0.2.tgz#b5fd54220aa2bc5ab57aab7140c940754503c1a7"