Strips visible utm_ strings off URLs on your site, but makes sure Google Analytics tracks them first

utmstrip.js

// utmstrip.js strips utm_* strings from the URL bar of your site, but afer Google Analytics 
// has had a chance to grab them. Based on Paul Irish's utm-stripping user script.
//
// Source: https://gist.github.com/elidickinson/9128677
//
// Install Notes:
// - This script should run *after* you have added all your "_trackPageview" or "_trackEvent" 
//    calls to the _gaq variable.
// - It doesn't matter of Google Analtyics has actually finished loading yet, but if you
//    you tell it to strip the utm_* strings before _trackPageview sees them, it won't know 
//    they were there.

// don't do anything if _gaq isn't even defined yet
if (((typeof _gaq != "undefined") && (typeof _gaq.push == "function"))) {
  // add the logic to strip utm tags to the _gaq command queue so that we can schedule
  // it to run after tracking calls to Google have already seen the utm values
  _gaq.push(function(){
    // ----- The below bit of showoff & magic is by Paul Irish's utmstrip.user.js v1.1
    //       See https://gist.github.com/paulirish/626834
    if (/utm_/.test(location.search) && window.history.replaceState){

      // thx @cowboy for the revised hash param magic.
      var oldUrl = location.href;
      var newUrl = oldUrl.replace(/\?([^#]*)/, function(_, search) {
        search = search.split('&').map(function(v) {
          return !/^utm_/.test(v) && v;
        }).filter(Boolean).join('&'); // omg filter(Boolean) so dope.
        return search ? '?' + search : '';
      });

      if ( newUrl != oldUrl ) {
        window.history.replaceState({},'', newUrl);
      }

    }
    // ----- end magic from https://gist.github.com/paulirish/626834
  })
}