Can script determine if window.onload has already fired?

11-19-2009

There is a discussion going on in the jquery-dev mailing list that
piqued my curiosity. I'm interested to know if the smart people here
have a good answer.

Is there a cross-browser way, in script, to determine if window.onload
has already fired?

If a script is lazy loaded and needs the DOM to be ready, it can
attach to the window's load event. But if that has already fired, then
the script's code will never run. Alternatively, it can just fire its
code inline, but the DOM may not be ready.

Thoughts?

Matt Kruse

11-19-2009

Matt Kruse wrote:

> There is a discussion going on in the jquery-dev mailing list that
> piqued my curiosity. I'm interested to know if the smart people here
> have a good answer.
>
> Is there a cross-browser way, in script, to determine if window.onload
> has already fired?
>
> If a script is lazy loaded and needs the DOM to be ready, it can
> attach to the window's load event.

But it should not. The loading state of the window has nothing to do with
the loading state of the document. We've been over this.

> But if that has already fired, then the script's code will never run.
> Alternatively, it can just fire its code inline, but the DOM may not be
> ready.
>
> Thoughts?

Smart people use the standards-compliant `onload' attribute instead.

PointedEars
--
Prototype.js was written by people who don't know javascript for people
who don't know javascript. People who don't know javascript are not
the best source of advice on designing systems that use javascript.
-- Richard Cornford, cljs, <f806at$ail$1$>

11-19-2009

On Nov 19, 12:30*pm, Thomas 'PointedEars' Lahn <PointedE...@web.de>
wrote:
> But it should not. *The loading state of the window has nothing to do with
> the loading state of the document. *We've been over this.

Fine then, substitute in any other method you prefer.

> Smart people use the standards-compliant `onload' attribute instead.

Could you be more specific?

Matt Kruse

11-19-2009

Matt Kruse wrote:

> Thomas 'PointedEars' Lahn wrote:
>> Smart people use the standards-compliant `onload' attribute instead.
>
> Could you be more specific?

<body onload="...">

PointedEars
--
realism: HTML 4.01 Strict
evangelism: XHTML 1.0 Strict
madness: XHTML 1.1 as application/xhtml+xml
-- Bjoern Hoehrmann

11-19-2009

On Nov 19, 1:06*pm, Thomas 'PointedEars' Lahn <PointedE...@web.de>
wrote:
> * <body onload="...">

Script cannot add itself to this attribute, though.

You're steering away from the real question, anyway. Regardless of
whether you feel it should be used, is there any cross-browser way to
detect if window.onload has already fired?

Matt Kruse

11-19-2009

On Nov 19, 3:07*pm, Matt Kruse <m...@thekrusefamily.com> wrote:
> On Nov 19, 1:06*pm, Thomas 'PointedEars' Lahn <PointedE...@web.de>
> wrote:
>
> > * <body onload="...">
>
> Script cannot add itself to this attribute, though.

Groan. Script doesn't have to "add itself" to this attribute.

>
> You're steering away from the real question, anyway.

Yes.

> Regardless of
> whether you feel it should be used, is there any cross-browser way to
> detect if window.onload has already fired?

Of course. Attach a load listener (or use the standard onload
attribute). They both do the same thing. One is proprietary and one
is not.

The proprietary window.onload property likely came about so that
scripts in the HEAD could set a load listener to the BODY before the
body is ready.

Now, how to know if the BODY load event has fired? Set a flag, of
course.

11-19-2009

On Nov 19, 12:55*pm, Matt Kruse <m...@thekrusefamily.com> wrote:

[...]

>
> If a script is lazy loaded and needs the DOM to be ready, it can
> attach to the window's load event. But if that has already fired, then
> the script's code will never run. Alternatively, it can just fire its
> code inline, but the DOM may not be ready.
>

And what sort of scheme are they working on where their scripts are
unclear about whether the load event has fired? Sounds like a recipe
for disaster to me.

<body onload="loaded = true;">

Or, as mentioned, set window.onload if you think that is a cooler,
more "unobtrusive" solution (despite the inherent drawbacks).

11-19-2009

David Mark wrote:

> On Nov 19, 3:07 pm, Matt Kruse <m...@thekrusefamily.com> wrote:
>> On Nov 19, 1:06 pm, Thomas 'PointedEars' Lahn <PointedE...@web.de>
>> wrote:
>> > <body onload="...">
>>
>> Script cannot add itself to this attribute, though.
>
> Groan. Script doesn't have to "add itself" to this attribute.

See below.

>> You're steering away from the real question, anyway.
>
> Yes.

No. I was just closing at it at a slower pace

>> Regardless of
>> whether you feel it should be used, is there any cross-browser way to
>> detect if window.onload has already fired?
>
> Of course. Attach a load listener (or use the standard onload
> attribute). They both do the same thing. One is proprietary and one
> is not.

But if we assume that, due to the flawed concept, there are only "lazy-
loaded" scripts, there is a chicken-and-the-egg problem with adding a load
listener with scripting. Hence my recommendation to use the `onload'
attribute of the `body' element in the first place.

> The proprietary window.onload property likely came about so that
> scripts in the HEAD could set a load listener to the BODY before the
> body is ready.

Unlikely: <http://docs.sun.com/source/816-6408-10/handlers.htm#1120545>

> Now, how to know if the BODY load event has fired? Set a flag, of
> course.

That is what I was aiming at. But some people apparently need it to be
spelt to them, so thank you for that.

PointedEars
--
Anyone who slaps a 'this page is best viewed with Browser X' label on
a Web page appears to be yearning for the bad old days, before the Web,
when you had very little chance of reading a document written on another
computer, another word processor, or another network. -- Tim Berners-Lee

11-19-2009

On Nov 19, 5:34*pm, Thomas 'PointedEars' Lahn <PointedE...@web.de>
wrote:
> David Mark wrote:
> > On Nov 19, 3:07 pm, Matt Kruse <m...@thekrusefamily.com> wrote:
> >> On Nov 19, 1:06 pm, Thomas 'PointedEars' Lahn <PointedE...@web.de>
> >> wrote:
> >> > <body onload="...">
>
> >> Script cannot add itself to this attribute, though.
>
> > Groan. *Script doesn't have to "add itself" to this attribute.
>
> See below.
>
> >> You're steering away from the real question, anyway.
>
> > Yes.
>
> No. *I was just closing at it at a slower pace

I figured. I'd just as soon be done with the discussion.

>
> >> Regardless of
> >> whether you feel it should be used, is there any cross-browser way to
> >> detect if window.onload has already fired?
>
> > Of course. *Attach a load listener (or use the standard onload
> > attribute). *They both do the same thing. *One is proprietary and one
> > is not.
>
> But if we assume that, due to the flawed concept, there are only "lazy-
> loaded" scripts, there is a chicken-and-the-egg problem with adding a load
> listener with scripting. *Hence my recommendation to use the `onload'
> attribute of the `body' element in the first place.

Right. The whole question is silly.

>
> > The proprietary window.onload property likely came about so that
> > scripts in the HEAD could set a load listener to the BODY before the
> > body is ready.
>
> Unlikely: <http://docs.sun.com/source/816-6408-10/handlers.htm#1120545>

I don't follow.

11-19-2009

On Nov 19, 11:34*pm, Thomas 'PointedEars' Lahn <PointedE...@web.de>
wrote:
>
> Unlikely: <http://docs.sun.com/source/816-6408-10/handlers.htm#1120545>

If you specify an onLoad event handler for an Image object that
displays a looping GIF animation (multi-image GIF), each loop of the
animation triggers the onLoad event, and the event handler executes
once for each loop.

Is this true ?
--
Jorge.

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