Re: How to pass a parameter via an image.onload function call?

[Janwillem Borleffs]

Tuxedo schreef:

However, this doesn't completely work, because the function
photo_preloaded (PARAMETER) will run regardless of whether the image
finished preloading or not. In normal cases, I do this kind of preloading
without parameters, which works fine, as follows:
>

You can check the Image.complete property; example:

img = new Image(100,100);
interval = setInterval('ch eckcomplete()', 100);
img.src = 'someimg';

function checkcomplete() {
if (window['img'].complete) {
alert(1);
clearInterval(w indow['interval']);
}
}


JW

[Thomas 'PointedEars' Lahn]

Re: How to pass a parameter via an image.onload function call?

Janwillem Borleffs wrote:

Tuxedo schreef:

>However, this doesn't completely work, because the function
>photo_preloade d(PARAMETER) will run regardless of whether the image
>finished preloading or not. In normal cases, I do this kind of preloading
>without parameters, which works fine, as follows:

>
You can check the Image.complete property;

But you should not. That property is not even remotely interoperable.
Instead, use the `onload' event handler:

var img = new Image(...);
img.onload = function() {
this.onload = null;
foo();
};
img.src = "...";

example:
>
img = new Image(100,100);

Always declare your identifiers.

interval = setInterval('ch eckcomplete()', 100);

setInterval() is defined as a method of Window objects, not of the Global
Object. Should be

window.setInter val(...)

However, window.setInter val() is error-prone and has a tendency to cause
extensive CPU load, especially with this short an interval (100 ms).
Repeated checking like this should be only the last resort.

img.src = 'someimg';
>
function checkcomplete() {
if (window['img'].complete) {

Never rely on that references to element objects can be retrieved through
same-named properties of `window' or the Global Object alone.

This will continue forever (and may accumulate timeouts, given enough DOM
action) if the `complete' property is unsupported (see above).

alert(1);
clearInterval(w indow['interval']);

You should not rely on that the object referred to by `window' is the
Variable Object of an execution context. Another property lookup is also
unnecessary here, the identifier lookup along the scope chain can take care
of it.

}
}

JFTR (the better solution is on the top):

var img = new Image(100, 100);
var interval = window.setInter val('checkcompl ete()', 100);
img.src = 'someimg';

function checkcomplete()
{
if (document.image s['img'].complete)
{
window.alert(1) ;
window.clearInt erval(interval) ;
}
}


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

[sasuke]

Re: How to pass a parameter via an image.onload function call?

On Oct 24, 1:07 am, Thomas 'PointedEars' Lahn <PointedE...@we b.de>
wrote:

window.setInter val(...)
>
However, window.setInter val() is error-prone and has a tendency to cause
extensive CPU load, especially with this short an interval (100 ms).
Repeated checking like this should be only the last resort.

Interesting; any links which discuss in detail the `error prone'
nature of window.setInter val()?

[Thomas 'PointedEars' Lahn]

Re: How to pass a parameter via an image.onload function call?

sasuke wrote:

Thomas 'PointedEars' Lahn wrote:

> window.setInter val(...)
>>
>However, window.setInter val() is error-prone and has a tendency to cause
>extensive CPU load, especially with this short an interval (100 ms).
>Repeated checking like this should be only the last resort.

>
Interesting; any links which discuss in detail the `error prone'
nature of window.setInter val()?

There are plenty of them in Google Groups, which you are using.


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$8 300dec7@news.de mon.co.uk>

[Jorge]

Re: How to pass a parameter via an image.onload function call?

On Oct 24, 6:58 pm, sasuke <database...@gm ail.comwrote:

On Oct 24, 1:07 am, Thomas 'PointedEars' Lahn <PointedE...@we b.de>
wrote:
>

  window.setInter val(...)

>

However, window.setInter val() is error-prone and has a tendency to cause
extensive CPU load, especially with this short an interval (100 ms).
Repeated checking like this should be only the last resort.

>
Interesting; any links which discuss in detail the `error prone'
nature of window.setInter val()?

It's not error-prone. It's just that *some* people don't understand
it.

If code sets a setInterval(f, n), the browser will keep pushing into
the timers' queue a call to f every n ms, regardless of whether the
queue is being serviced or not: remember: the browser is single-
threaded, and if it happens to be busy for a period of time longer
than n ms, the programmed calls can't/won't be executed yet. But
sooner or later the timer's queue will be serviced again and by then
there might be there hundreds or even thousands of queued calls to f
that will suddenly happen one after the other storm-like in a row
until the queue gets emptied again.

--
Jorge.

[sasuke]

Re: How to pass a parameter via an image.onload function call?

On Oct 25, 2:20 am, Jorge <jo...@jorgecha morro.comwrote:

On Oct 24, 6:58 pm, sasuke <database...@gm ail.comwrote:
>

On Oct 24, 1:07 am, Thomas 'PointedEars' Lahn <PointedE...@we b.de>
wrote:

>

  window.setInter val(...)

>

However, window.setInter val() is error-prone and has a tendency to cause
extensive CPU load, especially with this short an interval (100 ms).
Repeated checking like this should be only the last resort.

>

Interesting; any links which discuss in detail the `error prone'
nature of window.setInter val()?

>
It's not error-prone. It's just that *some* people don't understand
it.
>
If code sets a setInterval(f, n), the browser will keep pushing into
the timers' queue a call to f every n ms, regardless of whether the
queue is being serviced or not: remember: the browser is single-
threaded, and if it happens to be busy for a period of time longer
than n ms, the programmed calls can't/won't be executed yet. But
sooner or later the timer's queue will be serviced again and by then
there might be there hundreds or even thousands of queued calls to f
that will suddenly happen one after the other storm-like in a row
until the queue gets emptied again.

Ah, thanks for the explanation; this might just explain the erratic
nature of `setInterval'.

/sasuke

[Thomas 'PointedEars' Lahn]

Re: How to pass a parameter via an image.onload function call?

sasuke wrote:

On Oct 25, 2:20 am, Jorge <jo...@jorgecha morro.comwrote:

>On Oct 24, 6:58 pm, sasuke <database...@gm ail.comwrote:

>>On Oct 24, 1:07 am, Thomas 'PointedEars' Lahn <PointedE...@we b.de>
>>wrote:
>>> window.setInter val(...)
>>>However, window.setInter val() is error-prone and has a tendency to cause
>>>extensive CPU load, especially with this short an interval (100 ms).
>>>Repeated checking like this should be only the last resort.
>>Interesting ; any links which discuss in detail the `error prone'
>>nature of window.setInter val()?

>It's not error-prone. It's just that *some* people don't understand
>it.
>>
>If code sets a setInterval(f, n), the browser will keep pushing into
>the timers' queue a call to f every n ms, regardless of whether the
>queue is being serviced or not: remember: the browser is single-
>threaded, and if it happens to be busy for a period of time longer
>than n ms, the programmed calls can't/won't be executed yet. But
>sooner or later the timer's queue will be serviced again and by then
>there might be there hundreds or even thousands of queued calls to f
>that will suddenly happen one after the other storm-like in a row
>until the queue gets emptied again.

>
Ah, thanks for the explanation; this might just explain the erratic
nature of `setInterval'.

Don't listen to this wannabe.


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