W3C home > Mailing lists > Public > www-style@w3.org > February 2015

Re: [selectors] Proposal: :n-children() selector

From: Henrik Andersson <henke@henke37.cjb.net>
Date: Wed, 04 Feb 2015 06:15:56 +0100
Message-ID: <54D1AB0C.3090306@henke37.cjb.net>
To: "Tab Atkins Jr." <jackalmage@gmail.com>, Matt Mastracci <matthew@mastracci.com>
CC: Lea Verou <lea@verou.me>, www-style list <www-style@w3.org>
Tab Atkins Jr. skrev:
> That said, I'd actually prefer not to implement this.  Instead, I'd
> prefer to get custom selectors working (at least the declarative alias
> kind) as suggested in
> <http://dev.w3.org/csswg/css-extensions/#custom-selectors>, so people
> can do this themselves if they want it.  Doing this well requires
> going a little further than what is currently written in the doc, but
> all very believable - basically we need a way to handle plumbing
> arguments through from the "custom" pseudo to the expansion, and we
> need some better combinators to handle "self and/or siblings", etc.
> With that, you could do something like:
> @custom-selector $rest:--n-siblings($n)
> :nth-child(1):nth-last-child($n) /self-and-siblings/ $rest;
> So that writing `.foo:--n-siblings(3)` would become
> `:nth-child(1):nth-last-child(3) /self-and-siblings/ .foo` after
> expansion.
> ~TJ
Those selectors look scary. Simplicity helps authors get things right.

There is also a matter of performance. I don't know how to evaluate
performance, but one thing is clear: browsers have the opportunity to
optimize if they know what you are doing.
Received on Wednesday, 4 February 2015 05:16:29 UTC

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