fix(ga4): be robust against missing navigator.sendBeacon

packages/ga4/src/index.ts

@@ -349,7 +349,11 @@ function track(...args: any[]) {
 
   if (!trackingId) {
     console.error('GA4: Tracking ID is missing or undefined');
+    return;
+  }
 
+  if (!navigator.sendBeacon) {
+    console.warn('GA4: navigator.sendBeacon is not supported in this browser');
     return;
   }
 

packages/ga4/tests/index.test.ts

@@ -99,6 +99,24 @@ describe('ga4 -> track()', () => {
     expect(navigator.sendBeacon).not.toBeCalled();
   });
 
+  it.skip('logs an error message if sendBeacon is undefined', () => {
+    // It would be nice if we could test this, but sadly jest does not allow us to mock this
+    // property.
+    //
+    // Additionally, replaceProperty is only available in jest 29 and above, but since it doesn't
+    // work anyways we don't need this to force an upgrade.
+    //
+    // > Property `sendBeacon` is not declared configurable
+
+    // @ts-ignore
+    jest.replaceProperty(navigator, 'sendBeacon', undefined);
+
+    track(trackingId);
+
+    expect(errorSpy).toHaveBeenCalledWith(errorTrackingId);
+    expect(navigator.sendBeacon).not.toBeCalled();
+  });
+
   it('can be called directly with a tracking ID', () => {
     track(trackingId);