feat: Add google global site tag (gtag) adapter

src/adapters/google-ga.test.ts

@@ -1,9 +1,9 @@
-import { googleGA } from './google-ga';
+import { GA, googleGA } from './google-ga';
 
 declare global {
   namespace NodeJS {
     interface Global {
-      ga?: Function;
+      ga?: GA;
     }
   }
 }

src/adapters/google-ga.ts

@@ -3,13 +3,14 @@ import { EventProperties, EventTracker } from '../wrapped-analytics';
 // ga function signature:
 // ga('send', 'event', [eventCategory], [eventAction], [eventLabel], [eventValue], [fieldsObject]);
 // see https://developers.google.com/analytics/devguides/collection/analyticsjs/events#implementation
-interface GA {
+export interface GA {
   (
     method: string,
     type: string,
     eventCategory?: string,
     eventAction?: string,
     eventLabel?: string,
+    eventValue?: string,
     fieldsObject?: any,
   ): void;
 }

src/adapters/google-gtag.test.ts

@@ -0,0 +1,45 @@
+import { googleGTAG, GTAG } from './google-gtag';
+
+declare global {
+  namespace NodeJS {
+    interface Global {
+      gtag?: GTAG;
+    }
+  }
+}
+
+describe('googleGTAG', () => {
+  it('does nothing if Google Global Site Tag function not found', () => {
+    expect(() => {
+      googleGTAG('test');
+    }).not.toThrow();
+  });
+
+  it('maps event only', () => {
+    global.gtag = jest.fn();
+
+    googleGTAG('testEvent');
+
+    expect(global.gtag).toBeCalledWith('event', 'testEvent', {
+      event_category: undefined,
+      event_label: undefined,
+      value: undefined,
+    });
+  });
+
+  it('maps event and its properties', () => {
+    global.gtag = jest.fn();
+
+    googleGTAG('testEvent', {
+      category: 'testCategory',
+      label: 'testLabel',
+      value: 'testValue',
+    });
+
+    expect(global.gtag).toBeCalledWith('event', 'testEvent', {
+      event_category: 'testCategory',
+      event_label: 'testLabel',
+      value: 'testValue',
+    });
+  });
+});

src/adapters/google-gtag.ts

@@ -0,0 +1,43 @@
+import { EventProperties, EventTracker } from '../wrapped-analytics';
+
+// gtag function signature:
+// gtag('event', <action>, {
+//   'event_category': <category>,
+//   'event_label': <label>,
+//   'value': <value>
+// });
+// see https://developers.google.com/analytics/devguides/collection/gtagjs/events#send_events
+export interface GTAG {
+  (
+    type: string,
+    eventAction: string,
+    eventProperties?: {
+      event_category?: string;
+      event_label?: string;
+      value?: string;
+    },
+  ): void;
+}
+
+declare global {
+  interface Window {
+    gtag?: GTAG;
+  }
+}
+
+export const googleGTAG: EventTracker = (
+  event: string,
+  eventProperties?: EventProperties,
+): void => {
+  const gtag = window.gtag;
+  if (!gtag) {
+    return;
+  }
+
+  const { category, label, value } = eventProperties || ({} as EventProperties);
+  gtag('event', event, {
+    event_category: category,
+    event_label: label,
+    value: value,
+  });
+};