Puoi fare cosi
codice:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>Untitled</title>
<style type="text/css">
<!--
.hidden {display:none}
.show {display:block}
-->
</style>
</head>
<body>
<script language="JavaScript" type="text/javascript">
<!--
var lastNumero = 0;
function pippo(aSelect) {
numero = aSelect.value;
if (numero != '-') {
for (i=1;i<=numero;i++) {
curInputName = "t"+i;
document.getElementById(curInputName).className = "show";
} // for (i=1;i<=numero;i++)
for (j=parseInt(numero)+1;j<=5;j++) {
curInputName = "t"+j;
document.getElementById(curInputName).className = "hidden";
document.getElementById(curInputName).value = "";
} // for (j=numero;j<=5;j++)
lastNumero = numero;
} else {
aSelect.selectedIndex = lastNumero;
} //
}
//-->
</script>
<select id="sel1" onchange="pippo(this)">
<option value="-">Seleziona</option>
<option value="1">1</option>
<option value="2">2</option>
<option value="3">3</option>
<option value="4">4</option>
<option value="5">5</option>
</select>
<input type="text" class="hidden" id="t1">
<input type="text" class="hidden" id="t2">
<input type="text" class="hidden" id="t3">
<input type="text" class="hidden" id="t4">
<input type="text" class="hidden" id="t5">
</body>
</html>