A second argument to .closest to restrict how far the backwards traversing through the dom can go would be useful.

This would allow people to write something like:

$(#foo').click(function(e) {

var elm = $(e.target).closest('li', this);

...

});

In a case like this document:

<ul>

<li>

<ul id=foo>

<li>...</li>

</ul>

</li>

</ul>

If someone clicked directly on the ul#foo instead of the li (this is possible after the list has been styled) then the current .closest would falsely return the li which is a parent of the ul. Effectively using "this" as the restriction makes it so that tracing back through the dom never goes past the node we put the even on.

Ideally the restriction could be specified using a dom node, jQuery object, or selector (which would be matched as we walk along rather than traversing itself).