Re: [selectors4] Multiple subject indicators

> In numerous past discussions (sorry I cant scoop together links right
> now) it had been decided that the above would be an error.  In fact,
> IIRC it was one of the reasons for not using :has() which has been in
> jquery for... well... forever and was one of the original proposals
> from like 1999 or something.

There's absolutely no valid performance reason to do this. Since "a! + b! c" 
is just sugar for "a! + b c, a + b! c" it doesn't introduce any perf issue 
that the former doesn't already.

This is different from :has(...) which can have perf issues because you can 
use it to "return back down the DOM tree". In the case of "a:has(b):has(c)", 
you cannot simply apply a selector to an element to find out it has a parent 
which match a selector, because the second 'has' can reference an element 
that still hasn't been added to the DOM tree due to progressive rendering 
interruption. Therefore, you've to introduce a notion of state for :has(...) 
while the subject selector can be implemented stateless.

Received on Thursday, 13 June 2013 20:58:06 UTC