quiz.js

let questions = [
    {
        question: "Who owns Playstation?",
        answers: {
            A: "Sony",
            B: "Microsoft",
            C: "Google"
        },
        correct_answer: 'A'
    },
    {
        question: "Who owns Xbox?",
        answers: {
            D: "Apple",
            E: "Aperture Science",
            F: "Microsoft"
        },
        correct_answer: 'F'
    },
    {
        question: "Who owns Macintosh?",
        answers: {
            G: "Microsoft",
            H: "Apple",
            I: "Google"
        },
        correct_answer: 'H'
    },
    {
        question: "Which browser did Google create?",
        answers: {
            J: "Chrome",
            K: "FireFox",
            L: "Opera"
        },
        correct_answer: 'J'
    },
    {
        question: "Which OS did Linus Torvalds create?",
        answers: {
            M: 'OSX',
            N: 'Windows',
            O: 'Linux'
        },
        correct_answer: 'O'
    }
];

function create_quiz(questions, quiz_container, results_container, submit_button){
    function show_questions(questions, quiz_container){
        let output = [];
        let answers;

        for(let i = 0; i < questions.length; i++){
            answers = [];
            console.log("this is i:" + i);

            for(letter in questions[i].answers){
                console.log("This is letter: " + letter);
                answers.push(
                    '<label>'
                    + '<input type="radio>" name="question' + i + '" value="' + letter + '">'
                    + letter + ': '
                    + questions[i].answers[letter]
                  + '<label>'
                );
            }
        }
        quiz_container.innerHTML = output.join('');
    }

    function show_results(questions, quiz_container, results_container){
        let answer_containers = quiz_container.querySelectorAll('.answers');
        let user_answer = '';
        let num_correct = 0;
        for(let i = 0; i < questions.length; i++){
            console.log('show_results for loop i: ' + i);
            user_answer = answer_containers[i].querySelector('input[name=question'+i+']:checked'||{}).value;
            if(user_answer === questions[i].correct_answer){
                num_correct++;
                answer_containers[i].style.color = 'lightgreen';
            }
            else{
                answer_containers[i].style.color = 'red';
                console.log(answer_containers);
            }
        }
        results_container.innerHTML = num_correct + ' out of ' + questions.length;
    }

    show_questions(questions, quiz_container);

    submit_button.onclick = function(){
        show_results(questions, quiz_container, results_container);
    }
}

let quiz_container = document.getElementById('quiz');
let results_container = document.getElementById('results');
let submit_button = document.getElementById('submit');

create_quiz(questions, quiz_container, results_container, submit_button);