Thanks Alessandro for this overview. Sometimes one gets a bit lost in
the multiple options discussed :)
Sebastian
Alessandro Sala schrieb:
> Hi Jim,
>
>> I have never used a document.write() to load a script dynamically. I
>> create a DOM script object then set the src to the path of the script
>> I want to load. IE will execute the script immediately.
>>
>> var sc = document.createElement ('script');
>> document.body.appendChild(sc);
>> sc.src = 'somepathtoafile.js';
>>
>>
>> If you create a function out of this (recommended), the file is
>> included in the DOM when it hits the next </script> tag. This is a bug
>> in IE, you have to close a script in order for the newly created
>> script to be included in the DOM.
>>
> Thank you for your advice. Unfortunately I already tried to use this
> technique but it doesn't work
> reliably in IE while the document is being loaded.
>
> Let me summarize the whole thing:
>
> *The goal*
> Making the source build of a qooxdoo application work when the document
> type is XHTML.
>
> *The problem*
> The standard qooxdoo source loader uses document.write() to add <script
> src="..."> tags to the document being loaded, but the XHTML DOM does not
> support document.write(), so both FireFox and Opera fail to load the
> application. IE6 doesn't really support XHTML; if the document is served
> with the correct mimetype (application/xhtml+xml) it just shows the XML
> source, otherwise it parses the document as if it was HTML (since XHTML
> syntax is mostly compatibile with HTML 4), so document.write() works.
>
> *The (up to now) failed solutions*
> At first try, I simply used what you suggest (createElement and
> appendChild), but I found that, while it's perfectly ok in FireFox and
> Opera, it doesn't work reliably in IE6.
>
> The reason you, and others, see it working is probably because you
> create isolated script elements, that is scripts which don't depend one
> on another.
>
> On the contrary, the source scripts for qooxdoo classes need to be
> loaded in the correct order, which is determined at compile time, and
> which is reflected in the order used by the includer to to add script
> tags to the document being loaded.
>
> Given this, the problem with IE is that, while the document is being
> loaded, script elements added by createElement and appendChild don't get
> parsed in the same order they are created, but in an apparently random
> order: I suppose that the loading of such scripts from the network
> happens asynchronously, so the parsing order changes depending on system
> load, network latency and other unknown factors.
>
> This supposition is backed up by the fact that the problem disappears if
> you load the application locally from the filesystem (where the loading
> of files is probably synchronous), or if you insert an alert() after
> adding every script element (this suspends the execution, giving the
> added script the time to completely load before adding following one).
>
> Mainly following suggestions from Sebastian, I then then tried several
> other techniques (see my previous posts): you can find the document I
> used to test at http://www.alessandro.sala.mclink.net/inctest/ .
>
> Your suggestion is the second item (DOM-post): even if the first time
> the scripts happen to load in the correct order, if you keep reloading
> the page (or clicking on the relevant link) you will notice that
> sometimes the load order is wrong. Only the last link (document.write)
> always work.
>
> Here we only have 5 script included, so the probability of them being
> mis ordered is low, anyway it happens and if you download the page and
> the included scripts and test them with a local webserver the problem is
> even more evident; if you have much more scripts to load, such as
> qooxdoo classes (about 200), it is almost sure that some script will be
> loaded out of order, making the application fail to load.
>
> There is a working solution indeed: the load order is guaranteed if
> using a series of synchronous XMLHttpRequests to load the scripts and
> the eval()-ing them: but this means that the scripts get merged into a
> single document, losing the reference to their source filenames and line
> numbers, so the error messages from the browser become not much
> meaningful; in addition you can no more effectively use tool like
> Firebug to ease the development of applications and of qooxdoo itself.
>
> Given this, perhaps the only practicable solution is to keep using
> document.write() for IE6 while using DOM insertion for other browsers;
> it remains to see what will happen with IE7: does it really support
> XHTML, so document.write() will stop working? is the script loading
> order problem still present? If the answer to both questions is yes,
> then we have a problem.
>
> Sorry for the long message, but I hope this has clarified the problem a bit.
>
> Cheers,
> Alessandro
>
>
>
>
>
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