JS Luhn algorithm for node - functional style!

luhn-node.js

var luhn = function (number) {
    return number.split('').map(function (digit, index, arr) {
        return (index % 2 !== arr.length % 2) ? parseInt(digit, 10) : 2 * digit;
    }).reduce(function sum(val, cur, idx, arr) {
        return val + (cur < 10 ? parseInt(cur, 10) : (String(cur).split('').reduce(sum, 0)));
    }, 0) % 10;
};

exports.is_valid = function (number) {
    return luhn(number) === 0;
};