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JavaScript Object-Oriented JavaScript (2015) Practice Project Project Overview

David Mendiola
David Mendiola
Full Stack JavaScript Techdegree Student 16,579 Points

My honest solution

My solution the the oop quiz app, I honestly didn't look at Andrew's solution at all till the end and after viewing his answer I knew I could have optimized and automated things a bit more, definitely some good things I learned that I will apply.

I didn't use quiz_ui.js at all. I actually started using an array to store the "answers" but for the sake moving forward I just used answer1 and answer2. I thought to myself I definitely know how to access them arrays but the command would be super long. I wish I had though after seeing the answer.

I think the most difficult part of this project for me was how to validate the answer. I used the id of the element since it was unique to each answer.


function Question(question, firstAnswer, secondAnswer, correctAnswer){
    this.question = question;
    this.firstAnswer = firstAnswer;
    this.secondAnswer = secondAnswer;
    this.correctAnswer = correctAnswer;


function Quiz(){
    this.questions = [];    
    this.score = 0;
    this.currentQuestion = 0;
    //quiz always starts with at least 1 question
    this.progress = 1;
// adds question to quiz
Quiz.prototype.addQuestion = function(question){
// calculate quiz score
Quiz.prototype.updateScore = function(){
// get the users answer
Quiz.prototype.getAnswer = function(buttonClickId){
    var userAnswer;
    var quizQuestion = this.questions[this.currentQuestion];
    if (buttonClickId == "guess0"){
        userAnswer = quizQuestion.firstAnswer;
    if (buttonClickId == "guess1"){
        userAnswer = quizQuestion.secondAnswer;
    return userAnswer;
// check the users answer
Quiz.prototype.checkAnswer = function(buttonClickId){
    if (this.quizProgress()){
        var userAnswer = this.getAnswer(buttonClickId);
        var quizQuestion = this.questions[this.currentQuestion];
        if (userAnswer == quizQuestion.correctAnswer){
// check the quiz status
Quiz.prototype.quizProgress = function(){
    if (this.currentQuestion != this.questions.length){
        return true;
    } else {
        return false;
// load quiz
Quiz.prototype.load = function(questionEl, firstAnswerEl, secondAnswerEl, progressEl, quizEl){
    if (this.quizProgress()){
        questionEl.innerHTML = this.questions[this.currentQuestion].question;
        firstAnswerEl.innerHTML = this.questions[this.currentQuestion].firstAnswer;
        secondAnswerEl.innerHTML = this.questions[this.currentQuestion].secondAnswer;
        progressEl.innerHTML = "Question ";
        progressEl.innerHTML += this.progress;
        progressEl.innerHTML += " of ";
        progressEl.innerHTML += this.questions.length;
    } else {
        quizEl.innerHTML = "<h1>Gamer Over!</h1>";
        quizEl.innerHTML += "<h3>You score is: " + this.score;
        quizEl.innerHTML += "</h3>";


// create quiz
var quiz = new Quiz();
// create questions
var question1 = new Question("What color is the sky?", "Blue", "Red", "Blue");
var question2 = new Question("What is the current year?", 2016, 2017, 2017);
// add questions to quiz
// get quiz elements
var question = document.getElementById("question");
var firstAnswer = document.getElementById("choice0");
var secondAnswer = document.getElementById("choice1");
var progress = document.getElementById("progress");
var quizWrapper = document.getElementById("quiz");
// load quiz content first time
quiz.load(question, firstAnswer, secondAnswer, progress, quizWrapper);
// listen to answers
var guess0 = document.getElementById("guess0");
guess0.onclick = function(){
    quiz.load(question, firstAnswer, secondAnswer, progress, quizWrapper);
var guess1 = document.getElementById("guess1");
guess1.onclick = function(){
    quiz.load(question, firstAnswer, secondAnswer, progress, quizWrapper);

I'm definitely going to make this more automated but it was a great lesson overall.