add Google Analytics #53

klyburke · klyburke · commit 84a58c714a15 · 2018-04-14T13:57:16.000-07:00
diff --git a/pages/_document.js b/pages/_document.js
@@ -1,9 +1,26 @@
+/* eslint-disable react/no-danger */
+
 import React from 'react';
+import Router from 'next/router';
 import JssProvider from 'react-jss/lib/JssProvider';
 import Document, { Head, Main, NextScript } from 'next/document';
 
 import getContext from '../lib/context';
 
+require('dotenv').config();
+
+const gaTrackingId = 'process.env.GA_TRACKING_ID';
+
+Router.onRouteChangeComplete = () => {
+  if (window.gtag) {
+    window.gtag('config', window.gaTrackingId, {
+      page_location: window.location.href,
+      page_path: window.location.pathname,
+      page_title: window.document.title,
+    });
+  }
+};
+
 class MyDocument extends Document {
   render() {
     return (
@@ -61,6 +78,20 @@ class MyDocument extends Document {
               }
             `}
           </style>
+          <script async src={`https://www.googletagmanager.com/gtag/js?id=${gaTrackingId}`} />
+          <script
+            dangerouslySetInnerHTML={{
+              __html: `
+                window.gaTrackingId = '${gaTrackingId}';
+                window.dataLayer = window.dataLayer || [];
+                function gtag(){
+                  dataLayer.push(arguments);
+                }
+                gtag('js', new Date());
+                gtag('config', '${gaTrackingId}');
+              `,
+            }}
+          />
         </Head>
         <body
           style={{
