问需要对JavaScript课程进行一些澄清。(构造函数)

EN

(function() {
    function Question(question, answers, correct) {
        this.question = question;
        this.answers = answers;
        this.correct = correct;
    }

    Question.prototype.displayQuestion = function() {
        console.log(this.question);

        for (var i = 0; i < this.answers.length; i++) {
            console.log(i + ': ' + this.answers[i]);
        }
    }

    Question.prototype.checkAnswer = function(ans, callback) {
        var sc;

        if (ans === this.correct) {
            console.log('Correct answer!');
            sc = callback(true);
        } else {
            console.log('Wrong answer. Try again :)');
            sc = callback(false);
        }

        this.displayScore(sc);
    }

    Question.prototype.displayScore = function(score) {
        console.log('Your current score is: ' + score);
        console.log('------------------------------');
    }


    var q1 = new Question('Is JavaScript the coolest programming language in the world?',
                          ['Yes', 'No'],
                          0);

    var q2 = new Question('What is the name of this course\'s teacher?',
                          ['John', 'Micheal', 'Jonas'],
                          2);

    var q3 = new Question('What does best describe coding?',
                          ['Boring', 'Hard', 'Fun', 'Tediuos'],
                          2);

    var questions = [q1, q2, q3];

    function score() {
        var sc = 0;
        return function(correct) {
            if (correct) {
                sc++;
            }
            return sc;
        }
    }
    var keepScore = score();


    function nextQuestion() {

        var n = Math.floor(Math.random() * questions.length);
        questions[n].displayQuestion();

        var answer = prompt('Please select the correct answer.');

        if(answer !== 'exit') {
            questions[n].checkAnswer(parseInt(answer), keepScore);

            nextQuestion();
        }
    }

    nextQuestion();

})();