To length or not to length - that is the question

I needed to find a way to determine if a Silverlight app had been loaded in a div of an iframe. I wasted some time  trying to set a boolean flag and tracking events trying to get it set correctly. jQuery to the rescue! The consensus seems to be that this is the best way to check for the existence of a tag:

if ( $('#targetdiv').length > 0 )

or if you want to be tricky

if ( $('#targetdiv').length )

Of course, my target div was in an iframe so I used this:

if ( $('#ResultsFrame').contents().find('#silverlightControlHost').length > 0 )