sebastiansandqvist/s-valid

'use strict';

// ----- generic card validation
//        --    1. input must be a string
//        --    2. input length must be valid
//        --    3. perform check based on number
// ---------------------------------------
module.exports = function(str) {

    // [1] throws here if not a string
    str = str.toLowerCase();

    // [2] must be valid card length
    if (str.length < 13 || str.length > 19) {
        return false;
    }

    // [3] method of testing credit cards from
    // http://ajax.aspnetcdn.com/ajax/jquery.validate/1.13.1/jquery.validate.js
    var testNumber = 0;

    for (var i = str.length - 1, current, currentInteger = 0, even = false; i >= 0; i--) {
        
        current = str.charAt(i);
        currentInteger = parseInt(current, 10);

        if (even && (currentInteger *= 2) > 9) {
            currentInteger -= 9;
        }

        testNumber += currentInteger;
        even = !even;
    }

    return (testNumber % 10) === 0;

};