feat: add GTM integration

Author: bydawen

src/initialize.js

@@ -68,7 +68,7 @@ import {
 import {
   configure as configureAnalytics, SegmentAnalyticsService, identifyAnonymousUser, identifyAuthenticatedUser,
 } from './analytics';
-import { GoogleAnalyticsLoader } from './scripts';
+import { GoogleAnalyticsLoader, GoogleTagManagerLoader } from './scripts';
 import {
   getAuthenticatedHttpClient,
   configure as configureAuth,
@@ -269,8 +269,8 @@ function applyOverrideHandlers(overrides) {
  * @param {*} [options.analyticsService=SegmentAnalyticsService] The `AnalyticsService`
  * implementation to use.
  * @param {*} [options.authMiddleware=[]] An array of middleware to apply to http clients in the auth service.
- * @param {*} [options.externalScripts=[GoogleAnalyticsLoader]] An array of externalScripts.
- * By default added GoogleAnalyticsLoader.
+ * @param {*} [options.externalScripts=[GoogleAnalyticsLoader, GoogleTagManagerLoader]] An array of externalScripts.
+ * By default adds GoogleAnalyticsLoader and GoogleTagManagerLoader.
  * @param {*} [options.requireAuthenticatedUser=false] If true, turns on automatic login
  * redirection for unauthenticated users.  Defaults to false, meaning that by default the
  * application will allow anonymous/unauthenticated sessions.
@@ -290,7 +290,7 @@ export async function initialize({
   analyticsService = SegmentAnalyticsService,
   authService = AxiosJwtAuthService,
   authMiddleware = [],
-  externalScripts = [GoogleAnalyticsLoader],
+  externalScripts = [GoogleAnalyticsLoader, GoogleTagManagerLoader],
   requireAuthenticatedUser: requireUser = false,
   hydrateAuthenticatedUser: hydrateUser = false,
   messages,

src/scripts/GoogleTagManagerLoader.js

@@ -0,0 +1,48 @@
+/**
+ * @implements {GoogleTagManagerLoader}
+ * @memberof module:GoogleTagManagerLoader
+ */
+class GoogleTagManagerLoader {
+  constructor({ config }) {
+    this.gtmId = config.GOOGLE_TAG_MANAGER_ID;
+  }
+
+  loadScript() {
+    if (!this.gtmId) {
+      return;
+    }
+
+    global.google_tag_manager = global.google_tag_manager || [];
+    const { google_tag_manager: googleTagManager } = global;
+
+    // If the snippet was invoked do nothing.
+    if (googleTagManager.invoked) {
+      return;
+    }
+
+    // Invoked flag, to make sure the snippet
+    // is never invoked twice.
+    googleTagManager.invoked = true;
+
+    googleTagManager.load = (id) => {
+      const gtmScript = document.createElement('script');
+      gtmScript.type = 'text/javascript';
+      gtmScript.innerHTML = `
+        (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':
+        new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],
+        j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src=
+        'https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);
+        })(window,document,'script','dataLayer', '${id}');
+      `;
+
+      // Insert our scripts next to the first script element.
+      const first = document.getElementsByTagName('script')[0];
+      first.parentNode.insertBefore(gtmScript, first);
+    };
+
+    // Load gtmAnalytics.
+    googleTagManager.load(this.gtmId);
+  }
+}
+
+export default GoogleTagManagerLoader;

src/scripts/GoogleTagManagerLoader.test.js

@@ -0,0 +1,49 @@
+import GoogleTagManagerLoader from './GoogleTagManagerLoader';
+
+describe('GoogleTagManagerLoader', () => {
+  const mockGTMId = 'GOOGLE_TAG_MANAGER_ID_test_id';
+  let insertBeforeMock;
+
+  beforeEach(() => {
+    global.google_tag_manager = undefined;
+    insertBeforeMock = jest.fn();
+
+    document.getElementsByTagName = jest.fn(() => [
+      {
+        parentNode: {
+          insertBefore: insertBeforeMock,
+        },
+      },
+    ]);
+  });
+
+  it('should load GTM script', () => {
+    const loader = new GoogleTagManagerLoader({ config: { GOOGLE_TAG_MANAGER_ID: mockGTMId } });
+
+    loader.loadScript();
+
+    expect(global.google_tag_manager).toBeDefined();
+    expect(global.google_tag_manager.invoked).toBe(true);
+
+    const firstScript = document.getElementsByTagName()[0];
+    expect(firstScript.parentNode.insertBefore).toHaveBeenCalled();
+  });
+
+  it('should not load script if account is not defined', () => {
+    const loader = new GoogleTagManagerLoader({ config: { GOOGLE_TAG_MANAGER_ID: '' } });
+
+    loader.loadScript();
+
+    expect(global.google_tag_manager).toBeUndefined();
+  });
+
+  it('should not load script if google_tag_manager is already invoked', () => {
+    global.google_tag_manager = { invoked: true };
+    const loader = new GoogleTagManagerLoader({ config: { GOOGLE_TAG_MANAGER_ID: mockGTMId } });
+
+    loader.loadScript();
+
+    expect(global.google_tag_manager.invoked).toBe(true);
+    expect(document.getElementsByTagName).not.toHaveBeenCalled();
+  });
+});

src/scripts/index.js

@@ -1,2 +1,3 @@
 /* eslint-disable import/prefer-default-export */
 export { default as GoogleAnalyticsLoader } from './GoogleAnalyticsLoader';
+export { default as GoogleTagManagerLoader } from './GoogleTagManagerLoader';