If, for instance, someone were to do $("#someTable tr").closest("table"), the returned set will include the same ancestor table-element once for each row in the table, which is an undesirable and unexpected result. The set should be run through jQuery.unique, if necessary, to prevent this from happening.

A simple piece of code that illustrates this issue is

$('<div><span/><span/></div>').find('span').closest('div').length === 2