# Complex Regular Expression for a form validation

I have this form that validates with jquery & regular expressions...

``````...
//some code

var characterReg = /^([a-zA-Z0-9]{2,50})\$/; //only letters and numbers

if ( !characterReg.test(inputValName) ){

result.text('that\'s not a valid name!');

...
//more code``````

Now, I need a very specific validation of a field called 'NIF', wich is the identifier of a tax-paying company in my country. And I need some help to make a regular expression to use like I did in the above code.

So I found an old javascript code online that validates 'NIF':

``````function IsValidNIF(nif)
{
var c;
var checkDigit = 0;
//Check if is not null, is numeric and if has 9 numbers
if(nif != null && IsNumeric(nif) && nif.length == 9)
{
//Get the first number of NIF
c = nif.charAt(0);
//Check firt number is (1, 2, 5, 6, 8 or 9)
if(c == ‘1' || c == ‘2' || c == ‘5' || c == ‘6' || c == ‘8' || c == ‘9')
{
//Perform CheckDigit calculations
checkDigit = c * 9;
var i = 0;
for(i = 2; i <= 8; i++)
{
checkDigit += nif.charAt(i-1) * (10-i);
}
checkDigit = 11 - (checkDigit % 11);
//if checkDigit is higher than ten set it to zero
if(checkDigit >= 10)
checkDigit = 0;
//Compare checkDigit with the last number of NIF
//If equal the NIF is Valid.
if(checkDigit == nif.charAt(8))
return true;
}
}
return false;
}

function IsNumeric(ObjVal)
{
return /^\d+\$/.test(ObjVal);
}``````

So, is it possible to make a regular expression from this?

The rules are:

-must be only numbers
-must be 9 characters(numbers) long
-the first number must be 1 or 2 or 5 or 6 or 8 or 9
-the last number performs some validation(%module) that you should understand viewing the above code

Thank you.
ozo

-must be only numbers
-must be 9 characters(numbers) long
-the first number must be 1 or 2 or 5 or 6 or 8 or 9
characterReg = /^[125689][0-9]{8}\$/

-the last number performs some validation(%module) that you should understand viewing the above code
This part would produce a more complicated regular expression than is worth it, so I'd stick to using code.

What you mean " ...I'd stick to using code." ?

If possible let me know "how" complicated would the regex become. I don't mind if the regex is not "readable", the aproach of regex is just to cut some lines of code. Unless the regex could have some performance/other issues,. is that the case?

Thanks a lot.
I have to agree with ozo:  You're going to be attempting to reproduce modulo arithmetic via a regex. This isn't really what regex is designed for. The code approach would be much simpler. Just use ozo's suggested pattern, then add logic for the modulo check.

Thanks kaufed.

Then how would I add up the 2 things (regex + code) in my form?

Should be like:

``````...
//some code

var myRegex = /^[125689][0-9]{8}\$/;

if ( myRegex.test(inputValName) ){

// then implement other if here with the modulo% code??

...
//more code``````
``````String.prototype.ozo = function(i) { return this.charAt(i-1) * (10-i); }
function IsValidNIF(nif) {
var checkDigit = 0;
for(var i=1;i<9;i++) checkDigit += nif.ozo(i);
return /^[125689][0-9]{8}\$/.test(nif) && ((checkDigit%11 >= 21)?0:checkDigit == nif.charAt(8));
}``````

That's a little scary for my modest understanding of jquery.

Where do I put that code in the current code I have??

``````	<script>

function clearInput() {
\$("#myForm :input").each( function() {
\$(this).val('');
});
};

\$("#submitBtn").click( function() {

var result = \$('#result');
var company = \$('#myForm > #name-of-company');
var ai = \$('#myForm > #annual-income');
var characterReg = /^([a-zA-Z0-9]{2,50})\$/; //only letters and numbers
var aiReg = /^([0-9]{3,15})\$/; //only numbers
var inputVal = ai.val();
var inputValName = company.val();

if ( !characterReg.test(inputValName) ){

result.text('that\'s not a valid name!');

} else if ( !aiReg.test(inputVal) ) {

result.text('only numbers!');
company.removeClass('wrong');

} else {

\$.post( \$("#myForm").attr("action"),
\$("#myForm :input").serializeArray(),
function(info){ result.html(info);
});
clearInput();
company.removeClass('wrong');
ai.removeClass('wrong');

};

});

\$("#myForm").submit( function() {
return false;
});

</script>``````
There's no query here. You need to replace your current function by the one provided

but i a working with jquery here, I am more familiar with with. Don't know how to manipulate the DOM with pure js. Can I incorporate that function in my jquery?

Thanks
just replace your previous one, no more no less...