https://developers.google.com/analytics/devguides/collection/gajs/?hl=pl#MultipleCommands
_gaq.push(
['_setAccount', 'UA-XXXXX-1'],
['_trackPageview'],
['b._setAccount', 'UA-XXXXX-2'],
['b._trackPageview']
);
在此代码段中,有一个“.b”。“.b”来自哪里?我应该如何使用它?