Number validation in form field

[Matc]

Im working thorugh a variety a javascript problems and have managed to crack them - BUT ONE!

The problem is im trying to get a field to validate the number a user puts in it

The number of digits the user puts in will always be 6. However the 1st number must be either a 1 or 2. As 3 and onwards will be used for other sites. Anyone got any suggestions?

Much thanks

Mat

[ukgeoff]

The field content is always treated like a string even if its a number.

Therefors you can use string function to check the length of the number, ie, that it's six digits long and you can check that the sub-string, ie, the first character is one of the required numbers.

You need a combination of:

var checkStr = new String(document.getElementById('fieldID').value);

checkStr.length == 6;

checkStr.charAt(checkStr.0) == 1;

and so forth.

[Matc]

Thanks Geoff

Also just done it this way also, no one can enter a 5 digit code now and it cant be above 29999 also

<script language="JavaScript"><!--
function validate(what) {
what.output.value = '';

for (var i=0, len=what.input.value.length-1, valid='0123456789.' ; i<len ; i++) {
if (valid.indexOf(what.input.value.substring(i,i+1)) == -1) {
alert('invalid data');
return;
}
}
number = Math.floor(what.input.value - 0);
if (number > 29999 && number< 300000)
what.output.value = number;

else
alert('Invalid Account Number');
return;
}
function IsEmpty(aTextField) {
if ((aTextField.value.length==0) ||
(aTextField.value==null)) {
return true;
}
else { return false; }
}
//--></script>