Puoi fare cosi....
codice:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>Untitled</title>
<script language="JavaScript" type="text/javascript">
<!--
function generateTA() {
if (isNaN(document.getElementById('numTA').value)) {
alert('Il numero deve essere numerico');
return;
} // if (isNaN(document.getElementById('numTA').value))
if (document.getElementById('numTA').value != parseInt(document.getElementById('numTA').value)) {
alert('Il numero deve essere intero');
return;
} // if (document.getElementById('numTA').value != parseInt(gdocument.etElementById('numTA').value))
html = "";
nb = document.getElementById('numTA').value;
for (i=0;i<nb;i++) {
idTA = "ta"+i;
textTA = 'Textarea n°'+i+'<textarea rows="20" cols="50" id="'+idTA+'"></textarea>
';
html += textTA;
} // for (i=0;i<nb;i++)
document.getElementById('container').innerHTML ="";
document.getElementById('container').innerHTML =html;
}
//-->
</script>
</head>
<body>
<form action="" method="post">
N° di text area da creare
<input type="text" id="numTA" size="2">
<input type="button" value="ok" onclick="generateTA()">
<div id="container">
</div>
</form>
</body>
</html>