Add Google Tag Manager support (#178)

1 files changed, 54 insertions, 0 deletions

diff --git a/assets/js/gtm.js b/assets/js/gtm.js
new file mode 100644
index 0000000..4381ca9
--- /dev/null
+++ b/assets/js/gtm.js
@@ -0,0 +1,54 @@
+import {gtmCode, respectDoNotTrack} from '@params';
+
+/**
+ * Check if the Do Not Track setting is enabled.
+ *
+ * @returns {boolean}
+ */
+function isDoNotTrackEnabled() {
+  if (typeof window === 'undefined') {
+    return false;
+  }
+  const {doNotTrack, navigator} = window;
+
+  // Do Not Track Settings across browsers
+  const dnt = (doNotTrack || navigator.doNotTrack || navigator.msDoNotTrack);
+
+  if (!dnt) {
+    return false;
+  }
+
+  return dnt === true ||
+    dnt === 1 ||
+    dnt === 'yes' ||
+    (typeof dnt === 'string' && dnt.charAt(0) === '1');
+}
+
+if (respectDoNotTrack && isDoNotTrackEnabled()) {
+  // Skip analytics for users with Do Not Track enabled
+  console.info('[TRACKING]: Respecting DNT with respect to analytics...'); // eslint-disable-line no-console
+} else {
+  // Known DNT values not set, so we will assume it's off.
+  if (gtmCode) {
+    (function () {
+      const baseUrl = 'https://www.googletagmanager.com';
+      const params = new URLSearchParams({
+        id: gtmCode,
+        l: 'dataLayer'
+      });
+
+      const script = document.createElement('script');
+      script.src = `${baseUrl}/gtm.js?${params.toString()}`;
+      script.type = 'text/javascript';
+      script.async = true;
+
+      document.getElementsByTagName('head')[0].appendChild(script);
+
+      window.dataLayer = window.dataLayer || [];
+      window.dataLayer.push({
+        'gtm.start': new Date().getTime(),
+        event: 'gtm.js'
+      });
+    }());
+  }
+}