<script>
function isNumber(str,digits)
{
//var re=/^(-|\+)?\d+(\.\d+)?$/;
var re = new RegExp("^\\d*\\.?\\d{"+digits+"}$");
if(!re.test(str)){alert("不符合")}
}
</script>
<input type=text name=bao>
<input type=button onclick="isNumber(document.all.bao.value,2)">
function isNumber(str,digits)
{
//var re=/^(-|\+)?\d+(\.\d+)?$/;
var re = new RegExp("^\\d*\\.?\\d{"+digits+"}$");
if(!re.test(str)){alert("不符合")}
}
</script>
<input type=text name=bao>
<input type=button onclick="isNumber(document.all.bao.value,2)">
function IsNumeric(expression,digits)
{
var re = new RegExp("^(\\+|-)?\\d+(\\.\\d{"+digits +"})$");
return re.test(expression);
}
alert(IsNumeric("+123456.789", 3));
http://expert.csdn.net/Expert/TopicView1.asp?id=2489689