manually apply facebook/create-react-app#3934

config/webpack.config.dev.js

@@ -138,7 +138,33 @@ module.exports = {
               name: 'static/media/[name].[hash:8].[ext]',
             },
           },
-          // Process JS with Babel.
+          // Process WebWorkder JS with Babel.
+          // The preset includes JSX, Flow, and some ESnext features.
+          {
+            test: /\.worker\.(js|jsx|mjs)$/,
+            include: paths.appSrc,
+            use: [
+              require.resolve('worker-loader'),
+              // This loader parallelizes code compilation, it is optional but
+              // improves compile time on larger projects
+              require.resolve('thread-loader'),
+              {
+                loader: require.resolve('babel-loader'),
+                options: {
+                  // @remove-on-eject-begin
+                  babelrc: false,
+                  presets: [require.resolve('babel-preset-react-app')],
+                  // @remove-on-eject-end
+                  // This is a feature of `babel-loader` for webpack (not Babel itself).
+                  // It enables caching results in ./node_modules/.cache/babel-loader/
+                  // directory for faster rebuilds.
+                  cacheDirectory: true,
+                  highlightCode: true,
+                },
+              },
+            ],
+          },
+          // Process application JS with Babel.
           {
             test: /\.(js|jsx|mjs)$/,
             include: paths.appSrc,

config/webpack.config.prod.js

@@ -143,7 +143,32 @@ module.exports = {
               name: 'static/media/[name].[hash:8].[ext]',
             },
           },
-          // Process JS with Babel.
+
+          // Process WebWorker JS with Babel.
+          // The preset includes JSX, Flow, and some ESnext features.
+          {
+            test: /\.worker\.(js|jsx|mjs)$/,
+            include: paths.appSrc,
+            use: [
+              require.resolve('worker-loader'),
+              // This loader parallelizes code compilation, it is optional but
+              // improves compile time on larger projects
+              require.resolve('thread-loader'),
+              {
+                loader: require.resolve('babel-loader'),
+                options: {
+                  // @remove-on-eject-begin
+                  babelrc: false,
+                  presets: [require.resolve('babel-preset-react-app')],
+                  // @remove-on-eject-end
+                  compact: true,
+                  highlightCode: true,
+                },
+              },
+            ],
+          },
+
+          // Process application JS with Babel.
           {
             test: /\.(js|jsx|mjs)$/,
             include: paths.appSrc,

package.json

@@ -42,7 +42,8 @@
     "webpack": "3.8.1",
     "webpack-dev-server": "2.11.3",
     "webpack-manifest-plugin": "1.3.2",
-    "whatwg-fetch": "2.0.3"
+    "whatwg-fetch": "2.0.3",
+    "worker-loader": "^1.1.1"
   },
   "scripts": {
     "start": "node scripts/start.js",

yarn.lock

@@ -55,7 +55,7 @@ ajv-keywords@^2.0.0:
   version "2.1.1"
   resolved "https://registry.yarnpkg.com/ajv-keywords/-/ajv-keywords-2.1.1.tgz#617997fc5f60576894c435f940d819e135b80762"
 
-ajv-keywords@^3.0.0:
+ajv-keywords@^3.0.0, ajv-keywords@^3.1.0:
   version "3.2.0"
   resolved "https://registry.yarnpkg.com/ajv-keywords/-/ajv-keywords-3.2.0.tgz#e86b819c602cf8821ad637413698f1dec021847a"
 
@@ -68,7 +68,7 @@ ajv@^5.0.0, ajv@^5.1.5, ajv@^5.2.0, ajv@^5.3.0:
     fast-json-stable-stringify "^2.0.0"
     json-schema-traverse "^0.3.0"
 
-ajv@^6.0.1:
+ajv@^6.0.1, ajv@^6.1.0:
   version "6.5.4"
   resolved "https://registry.yarnpkg.com/ajv/-/ajv-6.5.4.tgz#247d5274110db653706b550fcc2b797ca28cfc59"
   dependencies:
@@ -4150,7 +4150,7 @@ loader-utils@^0.2.16:
     json5 "^0.5.0"
     object-assign "^4.0.1"
 
-loader-utils@^1.0.2, loader-utils@^1.1.0:
+loader-utils@^1.0.0, loader-utils@^1.0.2, loader-utils@^1.1.0:
   version "1.1.0"
   resolved "https://registry.yarnpkg.com/loader-utils/-/loader-utils-1.1.0.tgz#c98aef488bcceda2ffb5e2de646d6a754429f5cd"
   dependencies:
@@ -5881,6 +5881,13 @@ schema-utils@^0.3.0:
   dependencies:
     ajv "^5.0.0"
 
+schema-utils@^0.4.0:
+  version "0.4.7"
+  resolved "https://registry.yarnpkg.com/schema-utils/-/schema-utils-0.4.7.tgz#ba74f597d2be2ea880131746ee17d0a093c68187"
+  dependencies:
+    ajv "^6.1.0"
+    ajv-keywords "^3.1.0"
+
 select-hose@^2.0.0:
   version "2.0.0"
   resolved "https://registry.yarnpkg.com/select-hose/-/select-hose-2.0.0.tgz#625d8658f865af43ec962bfc376a37359a4994ca"
@@ -6915,6 +6922,13 @@ worker-farm@^1.3.1:
   dependencies:
     errno "~0.1.7"
 
+worker-loader@^1.1.1:
+  version "1.1.1"
+  resolved "https://registry.yarnpkg.com/worker-loader/-/worker-loader-1.1.1.tgz#920d74ddac6816fc635392653ed8b4af1929fd92"
+  dependencies:
+    loader-utils "^1.0.0"
+    schema-utils "^0.4.0"
+
 wrap-ansi@^2.0.0:
   version "2.1.0"
   resolved "http://registry.npmjs.org/wrap-ansi/-/wrap-ansi-2.1.0.tgz#d8fc3d284dd05794fe84973caecdd1cf824fdd85"