fermi.js

let questions = [];
let question = {};
let sources = {};
const question_bank_url =
    'https://raw.githubusercontent.com/EricAndrechek/FermiQuestions/main/question-bank.json';

// get question bank
function getQuestions() {
    fetch(question_bank_url)
        .then(function (response) {
            console.log(response);
            return response.json();
        })
        .then(function (json) {
            main(json);
        })
        .catch(function (ex) {
            console.log('parsing failed', ex);
            document.getElementById('fermi-question').innerHTML =
                'Failed to load question bank. Refresh clear your cache and reload the page to try again. <br>If this issue persists, please <a href="https://github.com/EricAndrechek/FermiQuestions/issues">report the issue</a>.';
        });
}

// shuffle question bank
function shuffleFisherYates(array) {
    let i = array.length;
    while (i--) {
        const ri = Math.floor(Math.random() * i);
        [array[i], array[ri]] = [array[ri], array[i]];
    }
    return array;
}

// get question from question bank and remove it from the bank
function getQuestion() {
    let qnumber = Number(document.getElementById('qnumber').innerHTML);
    question = questions.pop();
    document.getElementById('fermi-question').innerHTML = question.question;
    document.getElementById('qnumber').innerHTML = qnumber + 1;
}

// run code after page has loaded
function ready(fn) {
    if (document.readyState != 'loading') {
        fn();
    } else {
        document.addEventListener('DOMContentLoaded', fn);
    }
}

// page load
ready(function () {
    // get question bank and begin game setup
    getQuestions();
});

// receive question bank and shuffle it, beginning the game
function main(questions_json) {
    const raw_questions = questions_json['questions'];
    sources = questions_json['sources'];
    for (const source in raw_questions) {
        for (const q in raw_questions[source]) {
            questions.push({
                question: q,
                answer: raw_questions[source][q],
                source: source,
            });
        }
    }

    document.getElementById('tnumber').innerHTML = questions.length;
    questions = shuffleFisherYates(questions);
    getQuestion();
}

// listen for enter key to be pressed and run check_answer function
function enter(event) {
    if (event.which == 13 || event.keyCode == 13) {
        check_answer();
    }
}

// evaluate score and display message
function score_message(difference, answer) {
    let result = document.getElementById('result');
    let points = Number(document.getElementById('points').innerHTML);
    switch (difference) {
        case 0:
            result.className = '';
            result.classList.add('content', 'has-text-success');
            result.innerHTML = 'Correct! You were dead on and scored 5 points!';
            document.getElementById('points').innerHTML = points + 5;
            break;
        case 1:
            result.className = '';
            result.classList.add('content', 'has-text-warning');
            result.innerHTML =
                'Super Close! You were 1 away and scored 3 points. The correct answer was actually ' +
                answer +
                '.';
            document.getElementById('points').innerHTML = points + 3;
            break;
        case 2:
            result.className = '';
            result.classList.add('content', 'has-text-warning');
            result.innerHTML =
                'Almost! You were 2 away and scored 1 point. The correct answer was actually ' +
                answer +
                '.';
            document.getElementById('points').innerHTML = points + 1;
            break;
        default:
            result.className = '';
            result.classList.add('content', 'has-text-danger');
            result.innerHTML =
                'Not quite! You were ' +
                difference +
                " away and didn't score any points! The correct answer was actually " +
                answer +
                '.';
            break;
    }
}

// check if there are remaining questions
function game_over() {
    return questions.length === 0;
}

function display_end_game_text() {
    document.getElementById('fermi-question').innerHTML =
        "You've gone through all our fermi questions! Refresh the page to play again.";
    document.getElementById('fermi-answer').onkeypress = '';
    document.getElementById('fermi-button').onclick = '';
    document.getElementById('fermi-answer').disabled = true;
    document.getElementById('fermi-button').disabled = true;
}

// clear the answer field and prepare next question
function next_question() {
    document.getElementById('fermi-answer').value = '';

    if (!game_over()) {
        getQuestion();
    } else {
        display_end_game_text();
    }
}

// check answer to answer bank
function check_answer() {
    let answer = question['answer'];
    let userAnswer = document.getElementById('fermi-answer').value;
    let difference = Math.abs(answer - userAnswer);
    score_message(difference, answer);
    document.getElementById('fermi-source').innerHTML = source(question.source);
    next_question();
}

// get question source as a pretty string
function source(source) {
    const link = sources[source]['link'];
    const author = sources[source]['author'];
    const date = sources[source]['date'];
    return (
        '<a href="' +
        link +
        '" target="_blank">Previous question</a>' +
        ' sourced by ' +
        author +
        ' on ' +
        date
    );
}

// toggle the negative/positive sign on the answer field
function negate_answer() {
    document.getElementById('fermi-answer').value =
        -document.getElementById('fermi-answer').value;
}