iban.js

module.exports = {
    isValidIBANNumber: (input) => {
        var CODE_LENGTHS = {
            AD: 24,
            AE: 23,
            AT: 20,
            AZ: 28,
            BA: 20,
            BE: 16,
            BG: 22,
            BH: 22,
            BR: 29,
            CH: 21,
            CR: 21,
            CY: 28,
            CZ: 24,
            DE: 22,
            DK: 18,
            DO: 28,
            EE: 20,
            ES: 24,
            FI: 18,
            FO: 18,
            FR: 27,
            GB: 22,
            GI: 23,
            GL: 18,
            GR: 27,
            GT: 28,
            HR: 21,
            HU: 28,
            IE: 22,
            IL: 23,
            IS: 26,
            IT: 27,
            JO: 30,
            KW: 30,
            KZ: 20,
            LB: 28,
            LI: 21,
            LT: 20,
            LU: 20,
            LV: 21,
            MC: 27,
            MD: 24,
            ME: 22,
            MK: 19,
            MR: 27,
            MT: 31,
            MU: 30,
            NL: 18,
            NO: 15,
            PK: 24,
            PL: 28,
            PS: 29,
            PT: 25,
            QA: 29,
            RO: 24,
            RS: 22,
            SA: 24,
            SE: 24,
            SI: 19,
            SK: 24,
            SM: 27,
            TN: 24,
            TR: 26,
            AL: 28,
            BY: 28,
            CR: 22,
            EG: 29,
            GE: 22,
            IQ: 23,
            LC: 32,
            SC: 31,
            ST: 25,
            SV: 28,
            TL: 23,
            UA: 29,
            VA: 22,
            VG: 24,
            XK: 20
        };
        var iban = String(input).toUpperCase().replace(/[^A-Z0-9]/g, ''),
            code = iban.match(
                /^([A-Z]{2})(\d{2})([A-Z\d]+)$/
            ),
            digits;
        // check syntax and length
        if (!code || iban.length !== CODE_LENGTHS[code[1]]) {
            return false;
        }
        // rearrange country code and check digits, and convert chars to ints
        digits = (code[3] + code[1] + code[2]).replace(/[A-Z]/g, function(letter) {
            return letter.charCodeAt(0) - 55;
        });
        // final check
        return module.exports.mod97(digits);
    },
    mod97: (string) => {
        var checksum = string.slice(0, 2),
            fragment;
        for (var offset = 2; offset < string.length; offset += 7) {
            fragment = String(checksum) + string.substring(offset, offset + 7);
            checksum = parseInt(fragment, 10) % 97;
        }
        return checksum;
    }
}