Hi folks,
I've been working on a little jQuery powered MVC framework for the past
week and it really has started to produce some nice results. One of the
things I highly depend on is the ability to dynamically include
javascript files, and trigger a callback function when they are loaded.
Those need to load before the DOM does. I call this semi-asynchronous
loading.
Right now I have a function called jsInclude for this that is part of a
jCake 'singleton' class (using 'new function') which works really
beautifully in Firefox. However since about ~4 hours I've been trying to
get it to work under IE and only hit issues. So first please have a look
at the code:
----------------------------------------------------------------------------
// the variable 'self ' refers to the jCake class/ that this function is
a part of
this.jsInclude = function(jsInclude, callback, params, scope)
{
if (!params)
params = [];
else if(typeof(params)=='string')
params = [params];
for (i=0; i < self.jsIncludes.length; i++)
{
if (self.jsIncludes[i]==jsInclude)
{
callback.apply(self, params);
return;
}
}
var path = self.jsBaseUrl+jsInclude;
document.write('<script type="text/javascript"
src="'+path+'"></script>');
if (callback)
{
self.jsCallbacks.push({scope: scope || self, callback: callback,
params: params});
document.write('<script type="text/javascript">var callback =
jCake.jsCallbacks['+(self.jsCallbacks.length-1)+'];
callback.callback.apply(callback.scope, callback.params);</script>');
}
self.jsIncludes.push(jsInclude);
}
----------------------------------------------------------------------------
What it does is fairly simple, it dynamically adds a <script> tag to the
document using document.write and then, in case there is a callback
function it adds another script tag that should fire the callback when
the external <script> before it has loaded. This works in FF, but in IE
the callback will be triggered instantly. So I tried to work around this
in several ways: using the IE defer attribute for the script tag
<http://msdn.microsoft.com/workshop/author/dhtml/reference/properties/defer.asp>,
the onreadystatechange event
<http://www.outofhanwell.com/blog/index.php?title=the_window_onload_problem_revisited>
as well as using an additional external file. But no matter what I've
tried, it either resulted in the include becoming asynchronous (as
opposed to semi-asynchronous loading before the DOM), or into some mess
of IE errors that eventually brought up a white page (probably because
document.write was triggered after the DOM had loaded).
So for me this is the point to ask some of the JS ninjas around here if
they've been playing around with stuff like this before. Again, what I
need is a cross browser (let's say IE/FF) way to dynamically include JS
files before the DOM has loaded and registering an onload callback.
Meanwhile I'll go back to the drawing board and create a stand-alone
demo of the problem that I'll post here later on in case nobody can work
with the code I posted above.
-- Felix Geisendörfer aka the_undefined
--------------------------
http://www.thinkingphp.org
http://www.fg-webdesign.de
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