Forse cosi ( non so se esiste un metodo + semplice )
codice:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>Untitled</title>
<script language="JavaScript" type="text/javascript">
<!--
function conta() {
c = 0;
oColl = document.getElementsByTagName('INPUT');
for (i=0;i<oColl.length;i++) {
curInp = oColl.item(i);
if (curInp.type == 'text' && curInp.name.match(/^Campo[[]\d+[]]$/)) {
c++;
}
}
return c;
}
//-->
</script>
</head>
<body>
<form name="nomeMiaform">
<input type="text" name="Campo[0]">
<input type="text" name="Campo[1]">
<input type="text" name="Campo[2]">
<input type="text" name="Campo[122]">
<input type="text" name="Campo_[122]">
</form>
<script language="JavaScript" type="text/javascript">
<!--
alert(conta())
//-->
</script>
</body>
</html>