/**
 * function loadScript
 * Copyright (C) 2006-2007 Dao Gottwald
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 *
 * Contact information:
 *   Dao Gottwald  <dao at design-noir.de>
 *
 * @version  1.6
 * @url      http://design-noir.de/webdev/JS/loadScript/
 */

function loadScript(url, callback) {
	var f = arguments.callee;
	if (!("queue" in f))
		f.queue = {};
	var queue =  f.queue;
	if (url in queue) { // script is already in the document
		if (callback) {
			if (queue[url]) // still loading
				queue[url].push(callback);
			else // loaded
				callback();
		}
		return;
	}
	queue[url] = callback ? [callback] : [];
	var script = document.createElement("script");
	script.type = "text/javascript";
	script.onload = script.onreadystatechange = function() {
		if (script.readyState && script.readyState != "loaded" && script.readyState != "complete")
			return;
		script.onreadystatechange = script.onload = null;
		while (queue[url].length)
			queue[url].shift()();
		queue[url] = null;
	};
	script.src = url;
	document.getElementsByTagName("head")[0].appendChild(script);
}