Switch between no testing tool and something like Optimizely randomly and track it in GA

toolswitcher.js

(function (global) {

  // YOUR LIST OF TOOLS - REPLACE THE 'XXXXXXXXXX' WITH YOUR OPTIMIZELY PROJECT ID
  var yourTools = [ 
    {tool: "None" }, 
    { 

      tool: "optimizely",
      projectID: "XXXXXXXXXX"

  }];

  // CHECKS FOR EXISTING COOKIE ALONG WITH WHAT TOOL - IF ANY - SHOULD BE LOADED
  var toolSwitcher = global.cookie.replace(/(?:(?:^|.*;\s*)toolSwitcher\s*\=\s*([^;]*).*$)|^.*$/, "$1");

  // IF THE COOKIE EXISTS, IT GRABS ITS VALUE AND MAKES SURE TO ADD THE RIGHT TOOL - OR NONE.
  if (toolSwitcher) {
  
    addTool(toolSwitcher);

  } 

  // OR RANDOMLY PICKS ONE OF THE TOOS LISTED IN THE yourTools ARRAY OF OBJECTS
  else {
      
      var rand  = Math.floor(Math.random() * yourTools.length);

      // THE DIMENSION VALUE IS USED FOR GA AND THE COOKIE VALUE
      var dimensionValue = yourTools[rand].tool;

      setCookie(dimensionValue);
      addTool(yourTools[rand]);

      // RENAME "DIMENSION1" WITH THE CORRECT INDEX
      ga('set', 'dimension1', dimensionValue);

  }

      // SETS PERSISTENT COOKIE SO THAT WHATEVER WAS LOADED WILL BE THE EXPERIENCE THE USER HAS THROUGHOUT
      function setCookie(val) {
          var d = new Date();
          d.setTime(d.getTime() + (189216000000));
          var expires = d.toUTCString();
          var host = location.hostname;
          var path = "/";
          global.cookie = "toolSwitcher = " + val + "; domain = " + host + "; path = " + path + "; expires = " + expires;
      } 

      // ADDS THE RIGHT TOOL - OR NONE
      function addTool(tool) {
          if (tool.projectID) {
            var toolScript        = global.createElement("script");
            toolScript.type       = "text/javascript";
            toolScript.src        = "//cdn.optimizely.com/js/" + tool.projectID + ".js";
            var pageHead          = global.getElementsByTagName("head")[0];
            pageHead.insertBefore(toolScript, pageHead.firstChild);
          }
      }
  

}(document));