Someone

	<script type="text/javascript">
	
		Number.prototype.stringFormat = function( places )
		{
			if ( places == undefined )
				places = 2;
			
			var arr = this.toString().split(".");
			var num = arr[0];
			var dec = Math.round(arr[1]).toString().substring(0, places);
			var i, len, count = 0, str = "";
			var diff;
			
			for (i = 0, len = num.length; i < len; i++ )
			{
				diff = i - len;
				
				if ( diff % 3 == 0 )
					str += ",";
				
				str += num.substring(i, i + 1);
			}
			
			return( str +"."+ dec );
		}
		
		var num = 51232345.535324;
		alert(num +"\n\n"+ num.stringFormat());
	
	</script>