Multiple methodes

sendGrid.js

SendGridClient.prototype.send = function (message, parameters) {
    var deferred = when.defer();

    when(parameters,
        this._sendEmail.bind(this, deferred, message),
        function (error) {
            deferred.reject(error);
        }
    );

    return deferred.promise;
};

SendGrid.prototype._sendEmail = function(parameters, deferred, message) {
    var email = new SendGridEmail(parameters),
        categories = message.get("categories"),
        guid = guidGen();

    if (categories) {
        this._addCategories(email, categories);
    }

    this._sendGrid.send(email, function (success, errMessage) {
        if (!success) {
            deferred.reject({"error": errMessage, "action": "postpone"});
        } else {
            deferred.resolve(guid);
        }
    });
};

SendGridClient.prototype._addCategories = function(email, categories){
    var i;

    for (i in categories) {
        email.addCategory(categories[i]);
    }
};