NodeJS authentication generator required for PlacetoPay's Redirection (Web Checkout)

NodeJSAuthentication.js

var crypto = require('crypto');

/**
 * Generates authentication data in order to communicate with PlacetoPay Web Checkout service
 *
 * USAGE:
 *
 * var authGenerator = new RedirectionAuth("YOUR_LOGIN", "YOUR_TRANKEY");
 * var auth = authGenerator.asObject();
 *
 * IMPORTANT
 *
 * If you need to make another request and you have already the object instanciated, please make sure to
 * use the generate method BEFORE using the asObject again
 *
 * var auth = authGenerator.generate().asObject()
 *
 * @param login
 * @param tranKey
 * @constructor
 */
function RedirectionAuth(login, tranKey) {
    var self = this;
    var _nonce;
    var _seed;

    this.generate = function() {
        _nonce = Math.random().toString(36).substring(7);
        _seed = (new Date()).toISOString();
        return self;
    };

    this.getRealNonce = function() {
        return _nonce;
    };

    this.login = function() {
        return login;
    };

    this.nonce = function() {
        return new Buffer(_nonce).toString('base64');
    };

    this.seed = function() {
        return _seed;
    };

    this.tranKey = function() {
        return crypto.createHash('sha1').update(_nonce + seed + tranKey).digest('b64').toString('base64');
    };

    this.asObject = function() {
        return {
            "login": self.login(),
            "tranKey": self.tranKey(),
            "seed": self.seed(),
            "nonce": self.nonce()
        }
    };

    // For testing purposes

    this.setSeed = function(seed) {
        _seed = seed;
        return self;
    };

    this.setNonce = function(nonce) {
        _nonce = nonce;
        return self;
    };

    this.generate();
}

module.exports = RedirectionAuth;

Line 50 should be

return crypto.createHash('sha1').update(_nonce+ _seed + tranKey).digest('b64').toString('base64');

change seed to _seed

The seed format should be 'YYYY-MM-DDTHH:mm:ssZ' Line 29
_seed = (new Date()).toISOString();

I resolved it using moment (import momento before)
_seed = moment().format('YYYY-MM-DDTHH:mm:ssZ');