add resetSessionId method (#140)

* add resetSessionId method

* Add tests and update snippet

Author: djih

CHANGELOG.md

@@ -1,5 +1,7 @@
 ## Unreleased
 
+* Add `resetSessionId` method that sets the sessionId to the current time.
+
 ### 4.1.1 (March 22, 2018)
 
 * Fix bug where cookie data such as device id from older releases were not migrated

src/amplitude-client.js

@@ -707,6 +707,10 @@ AmplitudeClient.prototype.setSessionId = function setSessionId(sessionId) {
   }
 };
 
+AmplitudeClient.prototype.resetSessionId = function resetSessionId() {
+  this.setSessionId(new Date().getTime());
+};
+
 /**
   * Regenerates a new random deviceId for current user. Note: this is not recommended unless you know what you
   * are doing. This can be used in conjunction with `setUserId(null)` to anonymize users after they log out.

src/amplitude-snippet.js

@@ -24,7 +24,7 @@
                'setOptOut', 'setVersionName', 'setDomain', 'setDeviceId',
                'setGlobalUserProperties', 'identify', 'clearUserProperties',
                'setGroup', 'logRevenueV2', 'regenerateDeviceId',
-               'logEventWithTimestamp', 'logEventWithGroups', 'setSessionId'];
+               'logEventWithTimestamp', 'logEventWithGroups', 'setSessionId', 'resetSessionId'];
   function setUpProxy(instance) {
     function proxyMain(fn) {
       instance[fn] = function() {

test/amplitude-client.js

@@ -927,6 +927,31 @@ describe('setVersionName', function() {
     });
   });
 
+  describe('resetSessionId', function() {
+    let clock;
+
+    beforeEach(function() {
+      clock = sinon.useFakeTimers();
+    });
+
+    afterEach(function() {
+      reset();
+      clock.restore();
+    });
+
+    it('should reset the session Id', function() {
+      clock.tick(10);
+      amplitude.init(apiKey);
+
+      clock.tick(100);
+      amplitude.resetSessionId();
+
+      clock.tick(200);
+
+      assert.equal(amplitude._sessionId, 110);
+    });
+  });
+
   describe('identify', function() {
     let clock;
 

test/snippet-tests.js

@@ -53,4 +53,10 @@ describe('Snippet', function() {
     assert.deepEqual(amplitude._iq['instance2']._q[0], ['init', 'API_KEY2']);
     assert.deepEqual(amplitude._iq['instance2']._q[1], ['logEvent', 'Event']);
   });
+
+  it('amplitude object should proxy resetSessionId', function() {
+    amplitude.getInstance('reset_session_id_instance').init('API_KEY');
+    amplitude.getInstance('reset_session_id_instance').resetSessionId();
+    assert.deepEqual(amplitude._iq['reset_session_id_instance']._q[1], ['resetSessionId']);
+  });
 });