From 6777531a33bdad9f5427c8ab52da5c82239b1340 Mon Sep 17 00:00:00 2001
From: Daniel <daniel.berndt@gmail.com>
Date: Sat, 31 Mar 2018 13:27:21 +0200
Subject: [PATCH 1/3] Revert to use ecma 5 in uglifyOptions

---
 packages/react-scripts/config/webpack.config.prod.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/packages/react-scripts/config/webpack.config.prod.js b/packages/react-scripts/config/webpack.config.prod.js
index d631fc32a3b..78c733d002c 100644
--- a/packages/react-scripts/config/webpack.config.prod.js
+++ b/packages/react-scripts/config/webpack.config.prod.js
@@ -378,7 +378,7 @@ module.exports = {
     // Minify the code.
     new UglifyJsPlugin({
       uglifyOptions: {
-        ecma: 8,
+        ecma: 5,
         compress: {
           warnings: false,
           // Disabled because of an issue with Uglify breaking seemingly valid code:

From 0915f8858eddef19dfdb348d961803da5f45f066 Mon Sep 17 00:00:00 2001
From: Daniel <daniel.berndt@gmail.com>
Date: Sun, 1 Apr 2018 10:39:21 +0200
Subject: [PATCH 2/3] remove explicit ecma version from uglifyOptions settings

The defaults are already what we want
---
 packages/react-scripts/config/webpack.config.prod.js | 1 -
 1 file changed, 1 deletion(-)

diff --git a/packages/react-scripts/config/webpack.config.prod.js b/packages/react-scripts/config/webpack.config.prod.js
index 78c733d002c..3de05a29da4 100644
--- a/packages/react-scripts/config/webpack.config.prod.js
+++ b/packages/react-scripts/config/webpack.config.prod.js
@@ -378,7 +378,6 @@ module.exports = {
     // Minify the code.
     new UglifyJsPlugin({
       uglifyOptions: {
-        ecma: 5,
         compress: {
           warnings: false,
           // Disabled because of an issue with Uglify breaking seemingly valid code:

From 3cc48672ab354d3638fd8a35bac1ee6382ad1c2a Mon Sep 17 00:00:00 2001
From: Daniel <daniel.berndt@gmail.com>
Date: Mon, 2 Apr 2018 17:17:00 +0200
Subject: [PATCH 3/3] be explicit of where we use ecma: 8 and ecma: 5

---
 packages/react-scripts/config/webpack.config.prod.js | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/packages/react-scripts/config/webpack.config.prod.js b/packages/react-scripts/config/webpack.config.prod.js
index 3de05a29da4..e76f67d60d2 100644
--- a/packages/react-scripts/config/webpack.config.prod.js
+++ b/packages/react-scripts/config/webpack.config.prod.js
@@ -378,7 +378,15 @@ module.exports = {
     // Minify the code.
     new UglifyJsPlugin({
       uglifyOptions: {
+        parse: {
+          // we want uglify-js to parse ecma 8 code. However we want it to output
+          // ecma 5 compliant code, to avoid issues with older browsers, this is
+          // whey we put `ecma: 5` to the compress and output section
+          // https://github.com/facebook/create-react-app/pull/4234
+          ecma: 8,
+        },
         compress: {
+          ecma: 5,
           warnings: false,
           // Disabled because of an issue with Uglify breaking seemingly valid code:
           // https://github.com/facebook/create-react-app/issues/2376
@@ -390,6 +398,7 @@ module.exports = {
           safari10: true,
         },
         output: {
+          ecma: 5,
           comments: false,
           // Turned on because emoji and regex is not minified properly using default
           // https://github.com/facebook/create-react-app/issues/2488