From f7f9d77df6c3ba64c6d880b7cfb9dd55d59a7bb3 Mon Sep 17 00:00:00 2001
From: Schuyler Duveen <sky@skyb.us>
Date: Wed, 6 Jun 2018 11:21:28 -0400
Subject: [PATCH] use sendBeacon when available so that we can also send events
 reliably during beforeunload

---
 lib/index.js | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/lib/index.js b/lib/index.js
index 8728d3c..c08ecac 100644
--- a/lib/index.js
+++ b/lib/index.js
@@ -58,6 +58,17 @@ exports.type = cors ? 'xhr' : 'jsonp';
  */
 
 function json(url, obj, headers, timeout, fn) {
+  headers = headers || {};
+  if (navigator.sendBeacon
+      && Object.keys
+      && Object.keys(headers).length <= 1
+      && (!headers['Content-Type'] || headers['Content-Type'].indexOf('text/plain') > -1)) {
+    var res = navigator.sendBeacon(url, JSON.stringify(obj));
+    if (fn) {
+      fn(res ? null : { error: 'Failed to send' }, null);
+    }
+    return;
+  }
   var req = new XMLHttpRequest;
   req.onerror = fn;
   req.onreadystatechange = done;