Merge pull request #4 from segment-integrations/add-userId

push userId to data layer for track calls

Author: hankim813

lib/index.js

@@ -83,6 +83,9 @@ GTM.prototype.page = function(page) {
 
 GTM.prototype.track = function(track) {
   var props = track.properties();
+  var id = this.analytics.user().id();
+  if (id) props.userId = id;
   props.event = track.event();
+
   push(props);
 };

test/index.test.js

@@ -67,6 +67,12 @@ describe('Google Tag Manager', function() {
         analytics.called(window.dataLayer.push, { event: 'some-event' });
       });
 
+      it('should send userId if it exists', function() {
+        analytics.user().id('pablo');
+        analytics.track('some-event');
+        analytics.called(window.dataLayer.push, { userId: 'pablo', event: 'some-event' });
+      });
+
       it('should send event with properties', function() {
         analytics.track('event', { prop: true });
         analytics.called(window.dataLayer.push, { event: 'event', prop: true });