Revert "Revert "Add visitor support (#970)""

This reverts commit 373774d.

static/js/answers-experience.js

@@ -2,6 +2,7 @@ import DeferredPromise from './deferred-promise';
 import analyticsListener from './runtime-config-listeners/analytics';
 import sessionTrackingListener from './runtime-config-listeners/session-tracking';
 import querySourceListener from './runtime-config-listeners/query-source';
+import visitorListener from './runtime-config-listeners/visitor';
 
 /**
  * @typedef {import('./runtime-config.js').RuntimeConfigListener} RuntimeConfigListener
@@ -14,7 +15,8 @@ export default class AnswersExperience {
     this._runtimeConfigListeners = [
       analyticsListener,
       sessionTrackingListener,
-      querySourceListener
+      querySourceListener,
+      visitorListener
     ];
 
     this._registerRuntimeConfigListeners();

static/js/runtime-config-listeners/visitor.js

@@ -0,0 +1,9 @@
+/**
+ * @type {import('../runtime-config.js').RuntimeConfigListener}
+ */
+ export default {
+  key: 'visitor',
+  callback: value => {
+    ANSWERS.setVisitor(value);
+  }
+}

tests/static/js/answers-experience.js

@@ -0,0 +1,12 @@
+import AnswersExperience from '../../../static/js/answers-experience';
+import RuntimeConfig from '../../../static/js/runtime-config';
+
+describe('AnswersExperience works properly', () => {
+  it('visitor listener is called when visitor is set', () => {
+    const runtimeConfig = new RuntimeConfig();
+    const experience = new AnswersExperience(runtimeConfig);
+    const callListenerSpy = jest.spyOn(experience.runtimeConfig, '_callKeySpecificListeners');
+    experience.runtimeConfig.set('visitor', { id: '123', idMethod: 'test' });
+    expect(callListenerSpy).toHaveBeenCalledWith('update', 'visitor');
+  });
+});