🚀 go-pugleaf

Witam
Mam sobie takie coś:
function Answer(answer, explanation, type, validator) {
    this.answer = answer;
    this.explanation = explanation;
    this.type = type;
    this.validator = ('undefined' == validator ? null : validator);
}

function Question(question, explanation, type) {
    this.question = question;
    this.explanation = explanation;
    this.type = type;
    this.answers = new Array();
    
    this.addAnswer = function (answer, explanation, type, validator) {
        this.answers.push(new Answer(answer, explanation, type, validator));
    }
}

function Data(title, description) {
    this.title = title;
    this.description = description;
    this.questions = new Array();
    
    this.addQuestion = function (question_id, question, explanation, type) {
        this.questions[question_id] = new Question(question, explanation, type);
    }
    
    this.addAnswer = function (question_id, answer, explanation, type, validator) {
        this.questions[question_id].addAnswer(answer, explanation, type, validator);
    }
}

Następnie takie coś:
var data = new Data('tytul', 'opis');
for (var i=0; i<5; i++) {
    data.addQuestion(i, 'a'+i, 'b'+i, 'c'+i);
}

Na stronie dostaję błąd (firebug):
this.answers is undefined
        this.answers.push(new Answer(answer, explanation, type, validator));

Co robie zle? Jak sprawiść aby to zadziałało? 

A pozniej jeszcze dodać możliwość wstawiania odpowiedzi do pytań, czyli:
var data = new Data('tytul', 'opis');
for (var i=0; i<5; i++) {
    data.addQuestion(i, 'a'+i, 'b'+i, 'c'+i);
    for (var j=0; j<5; j++) {
        data.addAnswer(i, 'a'+j, 'b'+j, 'c'+j, 'd'+j);
    }
}

Z góry dziekuje za pomoc :D