CreditCardNumberChecker.ts

CreditCardNumberChecker.ts

type CardType = 'MasterCard' | 'Visa' | 'American Express' |
    'JCB' | 'Diners Club' | 'Discover' | 'unknown'

type MajorIndustryIdentifier =
    'ISO/TC 68' | 'Airlines' | 'Travel and entertainment and banking/financial' |
    'Banking and financial' | 'Merchandising and banking/financial' |
    'Petroleum' | 'Healthcare and telecommunications' | 'National assignment' |
    'unknown'

type CreditCardGuessedInformation = {
    complete: boolean, valid: boolean,
    cardType?: CardType, majorIndustryIdentifier?: MajorIndustryIdentifier
}

type CreditCardNumber = string

export const guessInformationFrom:
    (creditCardNumber: CreditCardNumber) => CreditCardGuessedInformation =
    (creditCardNumber: CreditCardNumber) => ({
        complete: getFullType(creditCardNumber) !== 'unknown',
        cardType: getFullType(creditCardNumber) !== 'unknown' ?
            getFullType(creditCardNumber) : getCreditCardType(creditCardNumber),
        majorIndustryIdentifier: getMajorIndustryIdentifier(creditCardNumber),
        valid: validate(creditCardNumber)
    })

const getCreditCardType: (number: CreditCardNumber) => CardType = (number) =>
    /^5[1-5]/.test(number) ? 'MasterCard' :
        /^4/.test(number) ? 'Visa' :
            /^3[47]/.test(number) ? 'American Express' :
                /^(?:2131|1800|35)/.test(number) ? 'JCB' :
                    /^3(?:0[0-5]|[68])/.test(number) ? 'Diners Club' :
                        /^6(?:011|5)/.test(number) ? 'Discover' : 'unknown'

const getFullType: (number: CreditCardNumber) => CardType = (number) =>
    /^5[1-5][0-9]{14}$/.test(number) ? 'MasterCard' :
        /^4[0-9]{12}(?:[0-9]{3})?$/.test(number) ? 'Visa' :
            /^3[47][0-9]{13}$/.test(number) ? 'American Express' :
                /^(?:2131|1800|35\d{3})\d{11}$/.test(number) ? 'JCB' :
                    /^3(?:0[0-5]|[68][0-9])[0-9]{11}$/.test(number) ? 'Diners Club' :
                        /^6(?:011|5[0-9]{2})[0-9]{12}$/.test(number) ? 'Discover' : 'unknown'


const validate: (number: CreditCardNumber) => boolean = (number) => {
    const checksum = parseInt(number.charAt(number.length - 1))
    const digits = number.substring(0, number.length - 1);

    const mod9 = [0, 1, 2, 3, 4, -4, -3, -2, -1, 0];
    let sum = 0;
    for (let i = 0; i < digits.length; i++) sum += parseInt(digits.substring(i, i + 1));
    for (let i = digits.length - 1; i >= 0; i -= 2) {
        sum += mod9[parseInt(digits.substring(i, i + 1))]
    }
    return 10 - sum % 10 === checksum
}

const getMajorIndustryIdentifier: (number: CreditCardNumber) => MajorIndustryIdentifier = (number) => {
    switch (parseInt(number.charAt(0))) {
        case 0:
            return 'ISO/TC 68';
        case 1:
        case 2:
            return 'Airlines';
        case 3:
            return 'Travel and entertainment and banking/financial';
        case 4:
        case 5:
            return 'Banking and financial';
        case 6:
            return 'Merchandising and banking/financial';
        case 7:
            return 'Petroleum';
        case 8:
            return 'Healthcare and telecommunications';
        case 9:
            return 'National assignment';
        default:
            return 'unknown'
    }
}