function $(cha)
{
	return document.getElementById(cha);
}

function checkall(check)
{
	checkthis = document.getElementsByName(check);
	for (i=0; i<checkthis.length; i++)
	{
		if (checkthis[i].checked)
		{
			checkthis[i].checked = false;
		}
		else
		{
			checkthis[i].checked = true;
		}
	}
}

String.prototype.trim = function()
{
	var reExtraSpace = /^\s*(.*?)\s+$/;
	return this.replace(reExtraSpace,"$1");
}

function preLoadImg(url)
{
	var img = new Image();
	img.src = url;
}