信用卡号码验证

Question

Hello I am having trouble with my javascript validation. I am trying to validate a credit card number which I want it to display between 13 and 18 numbers and single spaces.

My Javascript code:

<script type="text/javascript">
function validateForm()
{
var x=document.forms["checkout_details"]["creditcard"].value;
    if(x.length != 13 || x.length != 18)//if the length is not 13 or 18
    {
        alert("Please enter a valid credit card number");//display message to user;
        return false;
    }    
}
</script>

HTML/PHP Code:

echo '<form name="checkout_details" action="confirm.php" onsubmit="return validateForm()" method="post">';
echo '<font color="red">*</font>&nbsp;<b>Credit Card Number:</b> <input type="text" name="creditcard" id="creditcard"><br /><br />';
echo '<input type="submit" value="Purchase">';
echo '</form>';

Anyone help me out tell me what i'm doing wrong. Thanks.

Answer 1

Instead of

if(x.length != 13 || x.length != 18)

you should use

if(x.length != 13 && x.length != 18)

in fact, with your original condition, 18 is different from 13, and that would have returned true !

Also, that accepts only exact length of 13 or 18, if you want to reject anything shorter than 13 or longer than 18, then you need

if(x.length < 13 || x.length > 18)

Answer 2

You meant

if (x.length < 13 || x.length > 18) {
    ...
}

The original complains if the length is not exactly 13 and 18 characters; that is: always , as a string having length of 13 cannot have length of 18 and vice versa; also you want to match all the lengths in between.

Answer 3

Credit card validation is not that simple. You should use a regex to check it. There are also a large variety of credit card formats.

You can see the different regex' here Credit card regex'

Answer 4

不应该是：

if(x.length < 13 || x.length > 18)

Answer 5

Try this

if(x.length > 13 && x.length < 18) //if the length is between 13 and 18

There's also a very good plugin for CC validation here

jquery credit card validator

Answer 6

Validating credit cards is more than just the length of card number. To properly validate the card number (including the length), you should perform a check against the Luhn Algorithm. Use this code:

 const options = { method: 'GET', headers: {Accept: 'application/json', 'X-Api-Key': '[APIkey]'} }; fetch('https://api.epaytools.com/Tools/luhn?number=[CardNumber]&metaData=true', options).then(response => response.json()).then(response => console.log(response)).catch(err => console.error(err));