JavaScript: Validate Credit Card Number Using Regular Expressions and Luhn Check

Here is an example of validating a credit card number using JavaScript. Download the code along with the credit card icons: JSCREDITCARD.zip.

// returns true or false
function validateCreditCardNumber(cardNumber) {
	cardNumber = cardNumber.split(' ').join("");
	if (parseInt(cardNumber) <= 0 || (!/\d{15,16}(~\W[a-zA-Z])*$/.test(cardNumber)) || cardNumber.length > 16) {
		return false;
	}
	var carray = new Array();
	for (var i = 0; i < cardNumber.length; i++) {
		carray[carray.length] = cardNumber.charCodeAt(i) - 48;
	}
	carray.reverse();
	var sum = 0;
	for (var i = 0; i < carray.length; i++) {
		var tmp = carray[i];
		if ((i % 2) != 0) {
			tmp *= 2;
			if (tmp > 9) {
				tmp -= 9;
			}
		}
		sum += tmp;
	}
	return ((sum % 10) == 0);
}
function cardType(cardNumber) { // returns card type; should not rely on this for checking if a card is valid
	cardNumber = cardNumber.split(' ').join("");
    var o = {
        electron: /^(4026|417500|4405|4508|4844|4913|4917)\d+$/,
        maestro: /^(5018|5020|5038|5612|5893|6304|6759|6761|6762|6763|0604|6390)\d+$/,
        dankort: /^(5019)\d+$/,
        interpayment: /^(636)\d+$/,
        unionpay: /^(62|88)\d+$/,
        visa: /^4[0-9]{12}(?:[0-9]{3})?$/,
        mastercard: /^5[1-5][0-9]{14}$/,
        amex: /^3[47][0-9]{13}$/,
        diners: /^3(?:0[0-5]|[68][0-9])[0-9]{11}$/,
        discover: /^6(?:011|5[0-9]{2})[0-9]{12}$/,
        jcb: /^(?:2131|1800|35\d{3})\d{11}$/
    }
    for(var k in o) {
        if(o[k].test(cardNumber)) {
            return k;
        }
    }
	return null;
}

Coding Video

https://youtu.be/5Iovxzu3Qys

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