Javascript IBAN (International Bank Account Number) Validation

ibanvalidator.js

function validateIBAN(iban) {
    var newIban = iban.toUpperCase(),
        modulo = function (divident, divisor) {
            var cDivident = '';
            var cRest = '';

            for (var i in divident ) {
                var cChar = divident[i];
                var cOperator = cRest + '' + cDivident + '' + cChar;

                if ( cOperator < parseInt(divisor) ) {
                        cDivident += '' + cChar;
                } else {
                        cRest = cOperator % divisor;
                        if ( cRest == 0 ) {
                            cRest = '';
                        }
                        cDivident = '';
                }

            }
            cRest += '' + cDivident;
            if (cRest == '') {
                cRest = 0;
            }
            return cRest;
        };

    if (newIban.search(/^[A-Z]{2}/gi) < 0) {
        return false;
    }

    newIban = newIban.substring(4) + newIban.substring(0, 4);

    newIban = newIban.replace(/[A-Z]/g, function (match) {
        return match.charCodeAt(0) - 55;
    });

    return parseInt(modulo(newIban, 97), 10) === 1;
}

Failing on UK IBAN's sadly. Anyone got an idea about how to fix it?

I'm late at the party, but I'm shamelessly plugging my own lib for validating and formatting IBAN & BBAN: https://github.com/arhs/iban.js

Laurent, your code is very cool. I pasted it into an Apps Script "as is" and it works great with the following "test bench" code in the Code.gs file:

// Use the Apps Script IDE's "Run" menu to execute this code and then look at the View > Logs to see results.

function myFunction() {
//https://github.com/arhs/iban.js/blob/master/README.md
// var IBAN = require('iban');
var t1 = IBAN.isValid('hello world'); // false
var t2 = IBAN.isValid('BE68539007547034'); // true
var t3 = IBAN.isValid('BE68 5390 0754 7034'); // true

Logger.log("Test 1 = %s", t1);
Logger.log("Test 2 = %s", t2);
Logger.log("Test 3 = %s", t3);
}