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Re: Executing script-inserted external scripts in insertion order

From: Boris Zbarsky <bzbarsky@MIT.EDU>
Date: Mon, 18 Oct 2010 00:48:37 -0400
Message-ID: <4CBBD1A5.5040901@mit.edu>
To: Adam Barth <w3c@adambarth.com>
CC: public html <public-html@w3.org>
On 10/18/10 12:36 AM, Adam Barth wrote:
>> No, because that defers the scripts to onload.  The goal here is to execute
>> a set of scripts as soon from now as possible, but in a particular order.
>
> I believe defer doesn't wait until onload.  It just wants for parsing
> to be finished

Fair, it defers to DOMContentLoaded.  Which still introduces an 
undesirable ordering dependency on parser-created scripts, if nothing else.

> That's seems like a good balance of performance and predictability.

Good for whom?

> The scripts are loaded in parallel, but executed in order relative to
> each other and relative to inline / external scripts in the document.

This last is not desirable, as I understand.
>> 1)  Which change(s) are we talking about here??  There are at least 3
>> mutually exclusive proposed changes at this point, I think.
>
> Honestly, I'm lost w.r.t. all the proposals.

Yes, I can tell.

> There was something about an ordered property that I never understood.

It's been withdrawn.  Ignore it.

> There was a proposal to make non-async script-inserted scripts have order relative
> to themselves

Yes.

> There was a proposal to have async have different semantics on parser- and
> script-inserted scripts.

Also yes.  This proposal was a refinement of the "make non-async 
script-inserted scripts have order" proposal.

The third proposal was to require in-order execution of script-inserted 
scripts, period.  It sounds like you're unwilling to do that; fine.

>> 2)  I'd be interested in mention of actual sites that are slowed down by the
>> changes in question (esp. the one where async is just allowed to apply to
>> script-inserted stuff.
>
> Well, every site on the Internet that uses more than one
> script-inserted script without an async attribute.

And in which the timing at which the scripts run matters in a meaningful 
way (in that, say, the scripts aren't just loading API), right?

> The proposal was to add an ordering dependency between these scripts.

There have been three proposals.  At least one doesn't add such a 
dependency by default, but DOES allow the page to add it if desired.

> This has been advocated by web performance experts for a while.  For example, read
> this article:
>
> http://www.stevesouders.com/blog/2009/04/27/loading-scripts-without-blocking/

I'd love to, but all it says is:

   Error establishing a database connection

In any case, given your objections so far I think I'm on safe ground in 
saying that either you're not evaluating Henri's proposal to make async 
work on script-inserted scripts, or you misunderstood the proposal...

-Boris
Received on Monday, 18 October 2010 04:49:13 GMT

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