Determining whether jQuery has not found any element

$('#idThatDoesnotexist').length is what you're looking for. (If it finds nothing, this will === 0.) So your conditional statement should probably be:

if($('#id').length) { /* code if found */ } else { /* code if not found */ }

You're getting an object returned from that alert because jQuery (almost) always returns the "jQuery object" when you use it, which is a wrapper for the elements jQuery's found that permits method chaining.