View http://javascriptweblog.wordpress.com/2011/01/04/exploring-javascript-for-in-loops
I recall Googling for ways to loop through JavaScript objects countless times as I was becoming more familiar with the language. It’s one of those things that is a bit confusing at first, but at the same time illustrates the uniqueness of JavaScript itself. This fantastic article walks you through for-in loops in such a way you’ll likely not need to Google again.