Luhn Algorithm - Credit Card Validation

isValidCreditCard.js

var isValidCreditCard = function (card) {
 
    // Array I want to use to keep the transformed digits
    var momentaryCard = [];
    
    // Sum of transformed digits
    var sum = 0;
    
    // Card length
    var cardLength = card.length;

    // Index for loops
    var i;
        
    // Parse the card from the end, but from the second-last digit
    // Parse going by [i-2] we know we are getting the even digits
    // The [i] digits are odd
    for (i = cardLength - 2; i >= 0; i = i - 2) {

        // Get the even digits and multiple those digits x 2
        // 1 * 2, 8 * 2, 3 * 2, 2 * 2, 9 * 2 === 2, 16, 6, 4, 18
        momentaryCard.push(card[i] * 2);

        // Get the odd digits
        // 6 7 9 7 9 4
        momentaryCard.push(card[i + 1]);
 
    }
    
    // Add the first value if cardLength is odd
    if (cardLength % 2 !== 0) {
        momentaryCard.push(card[0]);
    }
    
    // Right now the momentaryCard is
    // [2, "6", 16, "7", 6, "9", 4, "7", 18, "9", "4"]
    // But we want every number separated: 1, 6 and not 16

    // ["2", "6", "1", "6", "7", "6", "9", "4", "7", "1", "8", "9", "4"]
    momentaryCard = momentaryCard.join('').split('');
 
    // Sum all the values
    for (i = 0; i < momentaryCard.length; i++) {
 
        sum += parseInt(momentaryCard[i]);
 
    };

    //sum is now === 70
 
    // if this return 0 Luhn passes, divisible by 10 with 0 rest
    return sum % 10 === 0;
 
};

console.log(isValidCreditCard('49927398716'));