You can't reliably use Array#concat on the _gaq object. Once Google Analytics loads, it replaces the _gaq array with a custom object that has it's own push() method. That object doesn't have concat() on it.
So, your core coding style will only work with very particular GA implementations; anything that deviates from that could very easily break or be subject to race conditions.
You'll also get better results if you use events rather than custom variables; custom variable reporting isn't as flexible and can be very confusing (ie, visit start). It'll also mitigate the need to use concat() to cut the line, since Events can be fired at any time (whereas custom variables need to happen before the first hit of the session to be well-reported).
I also really like the idea, though. I actually pass all my Optimizely test results as Google Analytics events with this snippet:
if (window.optimmizely && optimizely.variationNamesMap) {
var optmap = optimizely.variationNamesMap;
for (var expt in optmap) {
if (optmap.hasOwnProperty(expt)) {
_gaq.push(["_trackEvent", "Optimizely", optimizely.allExperiments[expt].name, optmap[expt], 0, true]);
}
}
}
Only if everyone loads it the same way. But there are lots of different ways to load GA; the only reason _gaq.push() isn't scary and doesn't raise the specter of race conditions is because of the 'spoofing' GA does.
There are LOTS of different versions of the GA snippet floating around the internet; the assumptions this configuration makes would only work for some of them.
Ok, now I understand what the issue is. I guess a good solution would be to pass _gaq to my library initializer and push every value with a for cycle, instead of using concat. Thanks for the tip.
So, your core coding style will only work with very particular GA implementations; anything that deviates from that could very easily break or be subject to race conditions.
You'll also get better results if you use events rather than custom variables; custom variable reporting isn't as flexible and can be very confusing (ie, visit start). It'll also mitigate the need to use concat() to cut the line, since Events can be fired at any time (whereas custom variables need to happen before the first hit of the session to be well-reported).
I also really like the idea, though. I actually pass all my Optimizely test results as Google Analytics events with this snippet: