<script type="text/javascript">
var formatDate = function (formatDate, formatString) {
	if(formatDate instanceof Date) {
		var months = new Array("Jan","Feb","Mar","Apr","May","Jun","Jul","Aug","Sep","Oct","Nov","Dec");
		var yyyy = formatDate.getFullYear();
		var yy = yyyy.toString().substring(2);
		var m = formatDate.getMonth();
		var mm = m < 10 ? "0" + m : m;
		var mmm = months[m];
		var d = formatDate.getDate();
		var dd = d < 10 ? "0" + d : d;

		var h = formatDate.getHours();
		var hh = h < 10 ? "0" + h : h;
		var n = formatDate.getMinutes();
		var nn = n < 10 ? "0" + n : n;
		var s = formatDate.getSeconds();
		var ss = s < 10 ? "0" + s : s;

		formatString = formatString.replace(/yyyy/i, yyyy);
		formatString = formatString.replace(/yy/i, yy);
		formatString = formatString.replace(/mmm/i, mmm);
		formatString = formatString.replace(/mm/i, mm);
		formatString = formatString.replace(/m/i, m);
		formatString = formatString.replace(/dd/i, dd);
		formatString = formatString.replace(/d/i, d);
		formatString = formatString.replace(/hh/i, hh);
		formatString = formatString.replace(/h/i, h);
		formatString = formatString.replace(/nn/i, nn);
		formatString = formatString.replace(/n/i, n);
		formatString = formatString.replace(/ss/i, ss);
		formatString = formatString.replace(/s/i, s);

		return formatString;
	} else {
		return "";
	}
}
</pre>

This will  show a demo date 

<pre lang="javascript">
alert(formatDate(new Date(), "d mmm yyyy hh:nn:ss"));