Comments on: Browser script loading roundup

By: Janghou

Janghou — Sat, 20 Mar 2010 09:37:54 +0000

@Steve: So Opera invented it, but doesn’t use it by default. Strange guys those Norwegians.

The Opera documentation you’re referring to is quite old. < 9.6*

The explanation Hallvord Steen gave in your comments against enabling it by default, http://www.stevesouders.com/blog/2008/09/11/delayed-script-execution-in-opera/#comment-255 should be applicable to other browsers as well.
Are you aware of any real world examples in which parallel loading actually breaks the website as Hallvord pointed out the danger for and which is a theoretical possibility not only in Opera?
Have you seen it break in Opera and work in another browser?
When that's not the case, it would say Opera does support it, but doesn't enable it by default, because theoretically it can break (badly designed) websites.

By: lnielsen

lnielsen — Thu, 11 Mar 2010 22:28:15 +0000

Is there any way to force the newer browser versions to disable parallel script loading?
I have a webpage that I use for performance testing that loads several small scripts and then one large, taking timings for both the small set and the large file, I need them to all use the same TCP session. (opens the TCP congestion window and then slams the network with 64KB)This works for IE7 but not FF3.5

By: Steve Souders

Steve Souders — Thu, 25 Feb 2010 17:56:16 +0000

@Janghou: Yes, you can read more about Opera and their support for deferring scripts that do document.write here: http://www.stevesouders.com/blog/2008/09/11/delayed-script-execution-in-opera/

However, since this is off by default and documentation says “Primarily for low bandwidth devices, not well-tested on desktop” it’s fairer to say Opera doesn’t support parallel script loading.

By: Janghou

Janghou — Wed, 24 Feb 2010 11:23:38 +0000

Opera has a config setting to allow parallel loading of scripts:
opera:config#Extensions|DelayedScriptExecution

It’s off by default, but enabling it gives the score as indicated by Gleb for Opera 10.10 as well.

I think you’re statement that Opera 10.10 blocks on all resource types, is therefore not completely right.

By: PHPGangsta

PHPGangsta — Sun, 14 Feb 2010 21:34:15 +0000

Thank you very much for that information, the comparison is very interesting and the Browserscope website is a very cool resource.

By: Simon Proctor

Simon Proctor — Wed, 10 Feb 2010 15:30:00 +0000

See if we could just get rid of document.write then it would work fine. You could run scripts without blocking the page.

Of course all the ad scripts would get very confused.

By: Gleb Arestov

Gleb Arestov — Tue, 09 Feb 2010 10:54:39 +0000

opera 10.5 ;) || script script = yes || script Stylesheet = yes || script Image = yes || script Iframe = yes

By: Lionel Pointet

Lionel Pointet — Mon, 08 Feb 2010 08:31:48 +0000

Hi ! I think this is very important, even if more and more efforts are made to launch JS at the bottom or to combine all the scripts in only one.

I have a little question : do you have some doc on how browsers behave in general? For example, is it more interesting to include an image with width and height in the CSS file or in the HTML tag itself?

Thank you (and also for rock music!).