Here is a little Class for dynamic import an JavaScript Class in the “<head>” Tag:
/*
* Simple Import Class
*
* Version 1.0 J.Sontag
* usage:
* $.classimport('your path to the file.js');
*/
(function($){
$.classimport = function(filename) {
try {
var write = true;
var check = $('head').find('script');
var len = check.length;
for ( var int = 0; int < len; int++) {
var root = check[int].src;
var index = root.lastIndexOf('/');
var src = root.substr(index+1,root.length);
var file = filename.substr(filename.lastIndexOf("/")+1,filename.length);
if(src == file){
write = false;
break;
}
}
if(write){
var head = document.getElementsByTagName('head')[0];
script = document.createElement('script');
script.src = filename;
script.type = 'text/javascript';
if ($.browser.mozilla) {
head.appendChild(script);
}else $('head').append(script);
return true;
}
else {
$.trace(file+" is already imported", "WARNING");
return false;
}
} catch (e) {
$.trace(e, "ERROR");
}
};
})(jQuery);

I developed a simple jQuery trace window for better debugging in JavaScript
Features:
use trace like in ActionScript anywhere in your js code:
$.trace(“something”);
turn all traces off just write:
$.setTrace(false);
Error & Warning in diffrent Colors write:
$.trace(“ERROR World”, “ERROR”);
$.trace(“Warning World”, “WARNING”);
if you want to see where the trace comes from:
$.setClassPath(value); here you can set a ClassPath if you want as ‘test.jquery.test.js’;
How to use it:
/*
* Dialog Trace Window
*
* usage:
*
* $.setTrace(value); true = on / false = off
* $.setClassPath(value); here you can set a ClassPath if you want as 'test.jquery.test.js';
* $.trace('your message',type); type = 'ERROR' or type= 'WARNING' not set = Normal Trace!
*
*/
<link rel="stylesheet" href="themes/trace.css">
<script type="text/javascript" src="js/jquery.min.js"></script>
<script type="text/javascript" src="js/jquery.trace.js"></script>
<script type="text/javascript" src="js/jquery-ui-1.8.13.custom.min.js"></script>
<script type="text/javascript">
$(function() {
$.setTrace(true);
$.setClassPath("your.path.to.show");
$.trace("Hello World");
$.trace("ERROR World", "ERROR");
$.trace("Warning World", "WARNING");
});
</script>
Try it out!
Download Demo