add merge Identities functionality

lib/mixpanel-node.d.ts

@@ -64,6 +64,8 @@ declare namespace mixpanel {
 
     alias(distinctId: string, alias: string, callback?: Callback): void;
 
+    merge(distinctIds: string, distinctId2: string, callback?: Callback): void;
+
     people: People;
 
     groups: Groups;

lib/mixpanel-node.js

@@ -434,6 +434,25 @@ var create_client = function(token, config) {
         metrics.track('$create_alias', properties, callback);
     };
 
+    /**
+     merge(distinct_id_1, distinct_id_2)
+     ---
+     This function merges 2 distinct_id s
+
+     For more information look at:
+     https://developer.mixpanel.com/reference/identity-merge
+
+     distinct_id_1:string              one distinct id
+     distinct_id_2:string              a second distinct id
+     */
+    metrics.merge = function(distinct_id_1, distinct_id_2, callback) {
+        var properties = {
+            distinct_ids: [distinct_id_1, distinct_id_2]
+        };
+
+        metrics.import('$merge', new Date().getDate(), properties, callback);
+    };
+
     metrics.groups = new MixpanelGroups(metrics);
     metrics.people = new MixpanelPeople(metrics);
 

test/merge.js

@@ -0,0 +1,39 @@
+var Mixpanel    = require('../lib/mixpanel-node'),
+    Sinon       = require('sinon');
+
+exports.merge = {
+    setUp: function(next) {
+        this.mixpanel = Mixpanel.init('token', { key: 'key' });
+
+        Sinon.stub(this.mixpanel, 'send_request');
+
+        next();
+    },
+
+    tearDown: function(next) {
+        this.mixpanel.send_request.restore();
+
+        next();
+    },
+
+    "calls send_request with correct endpoint and data": function(test) {
+        var distinct_id_1 = "distinct_id1",
+            distinct_id_2 = "distinct_id2",
+            expected_endpoint = "/import",
+            expected_data = {
+                event: '$merge',
+                properties: {
+                    distinct_ids: [distinct_id_1, distinct_id_2],
+                    token: 'token'
+                }
+            };
+
+        this.mixpanel.merge(distinct_id_1, distinct_id_2);
+        test.ok(
+            this.mixpanel.send_request.calledWithMatch({ endpoint: expected_endpoint, data: expected_data }),
+            "merge didn't call send_request with correct arguments"
+        );
+
+        test.done();
+    }
+};