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Re: Should MutationObservers be able to observe work done by the HTML parser?

From: Adam Klein <adamk@chromium.org>
Date: Fri, 15 Jun 2012 16:36:29 -0700
Message-ID: <CAEvLGcJe7WU2nWdYff+nYkAsY4kSxU9ejZ-ShG7BWsbvOeoSmw@mail.gmail.com>
To: WebApps WG <public-webapps@w3.org>
Cc: Olli@pettay.fi, Rafael Weinstein <rafaelw@chromium.org>
Re-sending from correct address:

On Fri, Jun 15, 2012 at 4:35 PM, Adam Klein <adamk@google.com> wrote:

> This code alerts in Firefox but not in Chrome:
> <!DOCTYPE html>
> <body>
>   <script>
>     var observer = new MutationObserver(function(r) {
>       alert(r);
>     });
>     observer.observe(document.body, {childList: true, subtree: true});
>   </script>
>   <p>Hello, World</p>
> </body>
> In WebKit's implementation, we had assumed that MutationObservers were
> meant to observe changes after page load (and I personally thought that
> we'd specced it that way, by putting it in DOM4, not HTML). But it seems
> the Mozilla implementors made a different assumption. But what should
> happen?
> IMHO, it may not be worth the gain may not be worth the possible
> performance degradation. If script wants to find out what the parser put on
> the page, it should wait for DOMContentLoaded. But I can imagine a use case
> where script might want to find out about the parser's work during load.
> In any case, we should try to come to a decision about this, since this
> seems to be the one major divergence between the existent implementations
> of MutationObservers.
> Thoughts?
> - Adam
Received on Friday, 15 June 2012 23:36:58 UTC

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