From a1613798f1c1434c571fc76ad554a3c324e471a9 Mon Sep 17 00:00:00 2001
From: Ricardo Amaral <master@ricardoamaral.net>
Date: Fri, 3 Nov 2017 03:29:36 +0000
Subject: [PATCH] Avoid serving the GA script to PageSpeed Insights
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Google PageSpeed Insights tool often shows a "Leverage Browser Caching"
penalization when one is using Google Analytics with the recommended
installation method. This sounds very counter-intuitive given that both
tools come from Google themselves.

This works around that issue by conditionally loading Google Analytics
only if the page is not being crawled by Google PageSpeed Insights bot.

Google is cheating me, so I'm cheating Google back... ¯\_(ツ)_/¯
---
 src/ssi/gtag.html | 27 +++++++++++++++++++++------
 1 file changed, 21 insertions(+), 6 deletions(-)

diff --git a/src/ssi/gtag.html b/src/ssi/gtag.html
index 9b00fab..1f8ff4c 100644
--- a/src/ssi/gtag.html
+++ b/src/ssi/gtag.html
@@ -1,9 +1,24 @@
-<!-- Global site tag (gtag.js) - Google Analytics -->
-<script async src="https://www.googletagmanager.com/gtag/js?id=UA-108806299-1"></script>
 <script>
-    window.dataLayer = window.dataLayer || [];
-    function gtag() { dataLayer.push(arguments); }
-    gtag('js', new Date());
+    if (navigator.userAgent.indexOf('Google Page Speed Insights') === -1) {
+        var TRACKING_ID = 'UA-108806299-1';
 
-    gtag('config', 'UA-108806299-1');
+        var gtagElement = document.createElement('script');
+
+        gtagElement.async = true;
+        gtagElement.src = 'https://www.googletagmanager.com/gtag/js?id=' + TRACKING_ID;
+
+        var scriptElements = document.getElementsByTagName('script');
+        var lastScriptElement = scriptElements[scriptElements.length - 1];
+
+        lastScriptElement.parentNode.insertBefore(gtagElement, lastScriptElement.nextSibling);
+
+        window.dataLayer = window.dataLayer || [];
+
+        function gtag() {
+            dataLayer.push(arguments);
+        }
+
+        gtag('js', new Date());
+        gtag('config', TRACKING_ID);
+    }
 </script>