function jsClass(action, id, aClass, bClass)
{
	var o = id;
	switch (action){
		case 'swap':
	      o.className=!jsClass('check',id,aClass,bClass) ? o.className.replace(bClass,aClass) : o.className.replace(aClass,bClass);
	    break;
		case 'add':
		  if(!jsClass('check',id,aClass)){o.className += o.className ? ' ' + aClass : aClass;}
		break;
		case 'remove':
		  var rep=o.className.match(' '+aClass)?' '+aClass:aClass;
		  o.className=o.className.replace(rep,'');
		break;
		case 'check':
		  return new RegExp('\\b'+aClass+'\\b').test(o.className)
		break;
	}
}

function changeImg(imgElement, img_src)
{
   imgElement.src = img_src;
}