javascript - Convert Google Analytics cookies to Local/Session Storage

Question

UPDATE http://jsfiddle.net/musicisair/rsKtp/embedded/result/

---

Google Analytics sets 4 cookies that will be sent with all requests to that domain (and ofset its subdomains). From what I can tell no server actually uses them directly; they're only sent with __utm.gif as a query param.

Now, obviously Google Analytics reads, writes and acts on their values and they will need to be available to the GA tracking script.

So, what I am wondering is if it is possible to:

• rewrite the __utm* cookies to local storage after ga.js has written them
• delete them after ga.js has run
• rewrite the cookies FROM local storage back to cookie form right before ga.js reads them
• start over

Or, monkey patch ga.js to use local storage before it begins the cookie read/write part.

Obviously if we are going so far out of the way to remove the __utm* cookies we'll want to also use the Async variant of Analytics.

I'm guessing the down vote was because I didn't ask a question. DOH!

My questions are:
Can it be done as described above?
If so, why hasn't it been done?

---

I have a default HTML/CSS/JS boilerplate template that passes YSlow, PageSpeed, and Chrome's Audit with near perfect scores. I'm really looking for a way to squeeze those remaining cookie bytes from Google Analytics in browsers that support local storage.

Answer 1

Use this:

(function(i,s,o,g,r,a,m){i['GoogleAnalyticsObject']=r;i[r]=i[r]||function(){
(i[r].q=i[r].q||[]).push(arguments)},i[r].l=1*new Date();a=s.createElement(o),
m=s.getElementsByTagName(o)[0];a.async=1;a.src=g;m.parentNode.insertBefore(a,m)
})(window,document,'script','//www.google-analytics.com/analytics.js','ga');

if(window.localStorage) {
    ga('create', 'UA-98765432-1', 'www.example.com', {
      'storage': 'none'
      , 'clientId': window.localStorage.getItem('ga_clientId')
    });
    ga(function(tracker) {
      window.localStorage.setItem('ga_clientId', tracker.get('clientId'));
    });
}
else {
    ga('create', 'UA-98765432-1', 'www.example.com');
}
ga('send', 'pageview');

First, I check if localStorage is supported. If it is supported then the 'storage': 'none' option will disable cookies. Now we can set the clientId from localStorage. If it is empty, Google Analytics will generate a new one for us. We save the new (or existing) clientid in localStorage after the tracker loads.

If localStorage is not supported, I just use the regular analytics method. After the initialization I send a pageView via ga('send', 'pageView').

Also, check out this plunk: http://plnkr.co/MwH6xwGK00u3CFOTzepK