In our case instanceof works perfectly (typeof doesn't since it always returns [object Object]). 

But I'm using this method as a constant solution for type checking. Here's the article of the guy who built it. It explains how it works, I think this was shared by Efrain a couple of weeks ago in DevsDo:

http://javascriptweblog.wordpress.com/2011/08/08/fixing-the-javascript-typeof-operator/