It would be handy to test if an element is a parent/child of another element. This is particularly useful when handling event bubbling to determine if an event has already been handled (this is the most reliable technique I have found to date that works in most modern browsers).

I expect it would look something like this:

jQuery('#blah').isAncestorOf(someElement) and jQuery('#blah').isDescendantOf(someElement)

Alternatively but less accurately it could be called isParentOf/isChildOf.

My existing JS implementation runs in logarithmic time and is as follows:

/** test if a is a descendant of b */

function isDescendantOf(a, b) {

return isAncestorOf(b, a);

}

/** test if a is an ancestor of b */

function isAncestorOf(a, b) {

// test if a is in b's parent chain

var o = b;

while (o) {

if (o === a)

return true;

o = o.parentNode;

}

return false;

}

Having this as part of jQuery would be convenient.