Victor Font replied 2 years ago

Before you use the $() notation, you have to convert this script to jQuery otherwise the $ will give you an error. The JavaScript equivalent to the $() is get_element_by_id()

Blaze P replied 2 years ago

Hi Bobby, Thank you for your reply.

I followed your directions but it does not seem to be working and I can feel I am missing something here. This is the code I am using in the Customize HTML form settings.

// Javascript program to implement Luhn algorithm

// Returns true if given
// card number is valid
function checkLuhn(cardNo)
{
let nDigits = cardNo.length;

let nSum = 0;
let isSecond = false;
for (let i = nDigits - 1; i >= 0; i--)
{

let d = cardNo[i].charCodeAt() - '0'.charCodeAt();

if (isSecond == true)
d = d * 2;

// We add two digits to handle
// cases that make two digits
// after doubling
nSum += parseInt(d / 10, 10);
nSum += d % 10;

isSecond = !isSecond;
}
return (nSum % 10 == 0);
}

let cardNo = "get_element_by_id("#field_[81]").val();";
if (checkLuhn(cardNo))
document.write("This is a valid card");
else
document.write("This is not a valid card");

This code is under the HTML code for the field.

Bobby Clapp replied 2 years ago

Could be a few things. First off though, you've listed a field ID in brackets. You need to get the field key and then no brackets would surround that value.

Something like:

let cardNo = "get_element_by_id("#field_js2dlv").val();