// general purpose function to see if a suspected numeric input
// is a positive or negative number

<SCRIPT>
function isNumber(inputVal) 
{

	oneDecimal = false;
	inputStr = inputVal.toString();
	for (var i = 0; i < inputStr.length; i++) 
        {
		var oneChar = inputStr.charAt(i)
		if (i == 0 && oneChar == "-") {
			continue
		}
		if (oneChar == "." && !oneDecimal) {
			if (inputStr.length == 1)
				return false
			oneDecimal = true
			continue
		}
		if (oneChar < "0" || oneChar > "9") {
			return false
		}
	}
	return true
}
document.write("<P>answer:" + isNumber("."));
document.write("<P>OK:");
</SCRIPT>