Allow [a-Z][0-9] only

[tom123]

//Ensure field only contains a-z, 0-9 charchters. Uses a regular expression to //validate data.
function validData(formField,fieldLabel)
{
var result = true;
var regExp = /[^a-z0-9]/i;

if (regExp.test(formField.value))
{
result = false;
alert('You may only enter alpha (a-z) and numeric (0-9) charcters for the "' + fieldLabel +'" field.');
formField.focus();
formField.select();
}

return result;
}

[Kor]

Nothing's new under the Sun. But it might be a better one. The classical Regexp validator might be something like this:

<script type="text/javascript">
function valid(field) {
var re = /^[0-9-A-z]*$/;
if (!re.test(field.value)) {
alert('Value must be only numbers or letters!');
field.value = field.value.replace(/[^0-9-A-z]/g,"");
}
}
</script>
....
<textarea name="text" cols="" rows="" onkeyup="valid(this)"></textarea>
...