CODEWITHSUNDEEP
javascripthtmlvalidation
Cyrus Dobbs
Cyrus Dobbs

Reputation: 48

Card number validation inconsistent error

I am producing a page that takes in a set of card details as a form. The fields need to be validated manually (without HTML 5) using JavaScript. The one problem I am having is with the 16 digit card number field.

I can't figure out why I am getting this inconsistant failier to validate. What is the problem with my code? Thanks.

HTML

<form onsubmit="submitDetails()">
        <input type="text" id="name" placeholder="Name" style="left:200px;position: absolute;"><br />
        <input type="text" id="cardNo" placeholder="Card Number" style="left:200px;position: absolute;"><br />
        <input type="text" id="expMonth" placeholder="MM" style="left:200px;position: absolute;">
        <input type="text" id="expYear" placeholder="YYYY" style="left:350px;position: absolute;"><br />
        <input type="text" id="secCode" placeholder="Security Code" style="left:200px;position: absolute;"><br />
        <input type="submit" id="submit" value="Submit Details" style="left:200px;position: absolute;">
    </form>

JavaScript

 var cardNo = document.getElementById('cardNo').value;

 if ((cardNo.toString().length != 16) || (isNaN(parseInt(cardNo)))){
            errorMsg += "\n\u2022 Enter a Card Number of 16 digits.\n"
 }

Upvotes: 0

Views: 82

Answers (2)

henrikmerlander
henrikmerlander

Reputation: 1574

From MDN:

If the first character cannot be converted to a number, parseInt returns NaN.

Upvotes: 0

Pointy
Pointy

Reputation: 413682

The parseInt() function parses an integer from the front of the string you give it. When it encounters something that's not part of a number, it stops and returns the value it's seen so far. Only if the string starts with something that cannot be interpreted as numeric will it return NaN.

Upvotes: 1

Related Questions