<html>
<head>
<title>formatando Cnpj em javascript</title>
<script type="text/javascript">
function FormataCnpj(campo, teclapres)
{
var tecla = teclapres.keyCode;
var vr = new String(campo.value);
vr = vr.replace(".", "");
vr = vr.replace("/", "");
vr = vr.replace("-", "");
tam = vr.length + 1;
if (tecla != 14)
{
if (tam == 3)
campo.value = vr.substr(0, 2) + '.';
if (tam == 6)
campo.value = vr.substr(0, 2) + '.' + vr.substr(2, 5) + '.';
if (tam == 10)
campo.value = vr.substr(0, 2) + '.' + vr.substr(2, 3) + '.' + vr.substr(6, 3) + '/';
if (tam == 15)
campo.value = vr.substr(0, 2) + '.' + vr.substr(2, 3) + '.' + vr.substr(6, 3) + '/' + vr.substr(9, 4) + '-' + vr.substr(13, 2);
}
}
</script>
</head>
<body>
<form method="post" action="arquivo.php">
<p>
<label>Cnpj:</data>
<input type="text" name="data" maxlength="18" onkeyup="FormataCnpj(this,event)" />
</p>
</form>
</body>
</html>
Referência: http://www.htmlstaff.org/ver.php?id=18522
