.closest() returns duplicates of the same element within the matched set.

[ajpiano]

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

[ajpiano]

I created a fix and did a pull request. ​http://github.com/ajpiano/jquery/commit/a2bd8a53f3a750606abea9bbb6ee2302437d42f3

[dmethvin]

See also #6384; should Sizzle remove dups or should jQuery remove them where they can occur?

[john]

Landed ​http://github.com/jquery/jquery/commit/a2bd8a53f3a750606abea9bbb6ee2302437d42f3

[ajpiano]

#7839 is a duplicate of this ticket.