add analytics handler (mixpanel)

README.md

@@ -174,6 +174,24 @@ Vue.use(VueAB, {
     Note: The expiry date is refreshed with every page visit. The entry only
     expires, if the user doesn't come back in the specified time.
 
+### Analytics options
+
+You can set an ***analytics handler***, on initialization. The only internally supported option currently is mixpanel, that will set a super property on the user like 'AB [test name]' equal to the wining slot name
+
+``` js
+Vue.use(VueAB, {
+  analytics: 'mixpanel'
+})
+```
+
+If you want to create your own ***analytics handler*** you can simply pass a function
+
+``` js
+Vue.use(VueAB, {
+  analytics: (name, winner) => console.log('AB Test', name, winner)
+})
+```
+
 ### Component Name
 
 By default `<split-test>` is the component that wraps a new test. This name can be overwritten on initialization:

package.json

@@ -8,8 +8,7 @@
     "build": "cross-env NODE_ENV=production rollup -c",
     "dev": "cross-env NODE_ENV=development rollup -cw"
   },
-  "dependencies": {
-  },
+  "dependencies": {},
   "devDependencies": {
     "cross-env": "^5.0.0",
     "rollup": "^0.41.4",

src/analytics.js

@@ -0,0 +1,15 @@
+
+function mixpanel (name, winner, countdown=100) {
+  if (window.mixpanel) {
+    var super_property = {}
+    super_property['A/B ' + name] = winner
+    window.mixpanel.register_once(super_property)
+  } else {
+    // loop until mixpanel is loaded
+    setTimeout(() => mixpanel(name, winner, countdown - 1), 1000)
+  }
+}
+
+export default {
+  mixpanel
+}

src/index.js

@@ -1,6 +1,6 @@
 import { storage, selectAB } from './persistence'
 import { randomCandidate } from './toolbox'
-
+import analytics from './analytics.js'
 const VueAB = {
   abtest: selectAB,
   randomCandidate,
@@ -28,6 +28,12 @@ const VueAB = {
           || randomCandidate(ctx.children)
 
         storage.entry = {name, winner}
+
+        if (analytics[options.analytics]) {
+          analytics[options.analytics](name, winner)
+        } else if (typeof options.analytics === "function"){
+          options.analytics(name, winner)
+        }
         return variations[winner]
       }
     })