From 81e1747469db83dd0832dae9199f0ee0583f6d73 Mon Sep 17 00:00:00 2001
From: Peter Dietrich <xosofox@gmail.com>
Date: Tue, 12 Dec 2017 07:45:35 +0100
Subject: [PATCH 1/2] try/catch xhr.responseType to avoid exception

The line can cause exceptions on Android 4.x in certain circumstances.

Unfortunately, not reproducible but only visible when logging client errors in production, see https://github.com/socketio/engine.io-client/issues/589
---
 lib/transports/polling-xhr.js | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/lib/transports/polling-xhr.js b/lib/transports/polling-xhr.js
index 297bac59e..a1c5a7b98 100755
--- a/lib/transports/polling-xhr.js
+++ b/lib/transports/polling-xhr.js
@@ -244,7 +244,10 @@ Request.prototype.create = function () {
             contentType = xhr.getResponseHeader('Content-Type');
           } catch (e) {}
           if (contentType === 'application/octet-stream') {
-            xhr.responseType = 'arraybuffer';
+            // next line can sometimes cause an exception in Android 4.x
+            try {
+              xhr.responseType = 'arraybuffer';
+            } catch (e) {}
           }
         }
         if (4 !== xhr.readyState) return;

From e47306004ced025409798e2e0a417349afa34aff Mon Sep 17 00:00:00 2001
From: Damien Arrachequesne <damien.arrachequesne@gmail.com>
Date: Thu, 4 Jan 2018 12:49:11 +0100
Subject: [PATCH 2/2] merge both try catch

---
 lib/transports/polling-xhr.js | 12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/lib/transports/polling-xhr.js b/lib/transports/polling-xhr.js
index a1c5a7b98..6044266a9 100755
--- a/lib/transports/polling-xhr.js
+++ b/lib/transports/polling-xhr.js
@@ -239,16 +239,12 @@ Request.prototype.create = function () {
     } else {
       xhr.onreadystatechange = function () {
         if (xhr.readyState === 2) {
-          var contentType;
           try {
-            contentType = xhr.getResponseHeader('Content-Type');
-          } catch (e) {}
-          if (contentType === 'application/octet-stream') {
-            // next line can sometimes cause an exception in Android 4.x
-            try {
+            var contentType = xhr.getResponseHeader('Content-Type');
+            if (contentType === 'application/octet-stream') {
               xhr.responseType = 'arraybuffer';
-            } catch (e) {}
-          }
+            }
+          } catch (e) {}
         }
         if (4 !== xhr.readyState) return;
         if (200 === xhr.status || 1223 === xhr.status) {