Trivia

Write a webpage that lets users answer trivia questions.

screenshot of trivia questions

Getting Started

Start by clicking inside your terminal window, then execute cd by itself. You should find that its “prompt” resembles the below.

Click inside of that terminal window and then execute

wget https://cdn.cs50.net/2023/fall/psets/8/trivia.zip

followed by Enter in order to download a ZIP called trivia.zip in your codespace. Take care not to overlook the space between wget and the following URL, or any other character for that matter!

Now execute

unzip trivia.zip

to create a folder called trivia. You no longer need the ZIP file, so you can execute

rm trivia.zip

and respond with “y” followed by Enter at the prompt to remove the ZIP file you downloaded.

Now type

cd trivia

followed by Enter to move yourself into (i.e., open) that directory. Your prompt should now resemble the below.

trivia/ $

If all was successful, you should execute

ls

and you should see an index.html file and a styles.css file.

If you run into any trouble, follow these same steps again and see if you can determine where you went wrong!

Implementation Details

Design a webpage using HTML, CSS, and JavaScript to let users answer trivia questions.

In index.html, add beneath “Part 1” a multiple-choice trivia question of your choosing with HTML.
- You should use an h3 heading for the text of your question.
- You should have one button for each of the possible answer choices. There should be at least three answer choices, of which exactly one should be correct.
Using JavaScript, add logic so that the buttons change colors when a user clicks on them.
- If a user clicks on a button with an incorrect answer, the button should turn red and text should appear beneath the question that says “Incorrect”.
- If a user clicks on a button with the correct answer, the button should turn green and text should appear beneath the question that says “Correct!”.
In index.html, add beneath “Part 2” a text-based free response question of your choosing with HTML.
- You should use an h3 heading for the text of your question.
- You should use an input field to let the user type a response.
- You should use a button to let the user confirm their answer.
Using JavaScript, add logic so that the text field changes color when a user confirms their answer.
- If the user types an incorrect answer and presses the confirmation button, the text field should turn red and text should appear beneath the question that says “Incorrect”.
- If the user types the correct answer and presses the confirmation button, the input field should turn green and text should appear beneath the question that says “Correct!”.

Optionally, you may also:

Edit styles.css to change the CSS of your webpage!
Add additional trivia questions to your trivia quiz if you would like!

Walkthrough

This video was recorded when the course was still using CS50 IDE for writing code. Though the interface may look different from your codespace, the behavior of the two environments should be largely similar!

Hints

Use document.querySelector to query for a single HTML element.
Use document.querySelectorAll to query for multiple HTML elements that match a query. The function returns an array of all matching elements.

Not sure how to solve?

Testing

No check50 for this one, as implementations will vary based on your questions! But be sure to test both incorrect and correct responses for each of your questions to ensure that your webpage responds appropriately.

Run http-server in your terminal while in your trivia directory to start a web server that serves your webpage.

How to Submit

Download your index.html and styles.css files by control-clicking or right-clicking on the file in your codespace’s file browser and choosing Download.
Go to CS50’s Gradescope page.
Click “Problem Set 8: Trivia”.
Drag and drop your index.html and styles.css files to the area that says “Drag & Drop”. Be sure they have those exact filenames! If you upload a file with a different name, the autograder likely will fail when trying to run it, and ensuring you have uploaded files with the correct filenames is your responsibility!
Click “Upload”.

You should see a message that says “Problem Set 8: Trivia submitted successfully!”

Per Step 4 below, after you submit, be sure to check your autograder results. If you see SUBMISSION ERROR: missing files (0.0/1.0), it means your file was either not named exactly as prescribed, you uploaded it to the wrong problem, or you did not include all files.

Correctness in submissions entails everything from reading the specification, writing code that is compliant with it, and submitting all files with the correct names. If you see this error, you should resubmit right away, making sure your submission is fully compliant with the specification. The staff will not adjust your filenames nor upload files for you after the fact!

Want to see the staff’s solution? You can find two ways of solving the problem here!

Creating event listeners with JavaScript

<!DOCTYPE html>

<html lang="en">
    <head>
        <link href="https://fonts.googleapis.com/css2?family=Montserrat:wght@500&display=swap" rel="stylesheet">
        <link href="styles.css" rel="stylesheet">
        <title>Trivia!</title>
        <script>

            // Wait for DOM content to load
            document.addEventListener('DOMContentLoaded', function() {

                // Get all elements with class "correct"
                let corrects = document.querySelectorAll('.correct');

                // Add event listeners to each correct button
                for (let i = 0; i < corrects.length; i++) {
                    corrects[i].addEventListener('click', function() {

                        // Set background color to green
                        corrects[i].style.backgroundColor = 'Green';

                        // Go to parent element of correct button and find the first element with class "feedback" which has that parent
                        corrects[i].parentElement.querySelector('.feedback').innerHTML = 'Correct!';
                    });
                }

                // When any incorrect answer is clicked, change color to red.
                let incorrects = document.querySelectorAll(".incorrect");
                for (let i = 0; i < incorrects.length; i++) {
                    incorrects[i].addEventListener('click', function() {

                        // Set background color to green
                        incorrects[i].style.backgroundColor = 'Red';

                        // Go to parent element of correct button and find the first element with class "feedback" which has that parent
                        incorrects[i].parentElement.querySelector('.feedback').innerHTML = 'Incorrect';
                    });
                }

                // Check free response submission
                document.querySelector('#check').addEventListener('click', function() {
                    let input = document.querySelector('input');
                    if (input.value === 'Switzerland') {
                        input.style.backgroundColor = 'green';
                        input.parentElement.querySelector('.feedback').innerHTML = 'Correct!';
                    }
                    else {
                        input.style.backgroundColor = 'red';
                        input.parentElement.querySelector('.feedback').innerHTML = 'Incorrect';
                    }
                });
            });
        </script>
    </head>
    <body>
        <div class="header">
            <h1>Trivia!</h1>
        </div>

        <div class="container">
            <div class="section">
                <h2>Part 1: Multiple Choice </h2>
                <hr>
                <h3>What is the approximate ratio of people to sheep in New Zealand?</h3>
                <button class="incorrect">6 people per 1 sheep</button>
                <button class="incorrect">3 people per 1 sheep</button>
                <button class="incorrect">1 person per 1 sheep</button>
                <button class="incorrect">1 person per 3 sheep</button>
                <button class="correct">1 person per 6 sheep</button>
                <p class="feedback"></p>
            </div>

            <div class="section">
                <h2>Part 2: Free Response</h2>
                <hr>
                <h3>In which country is it illegal to own only one guinea pig, as a lone guinea pig might get lonely?</h3>
                <input type="text"></input>
                <button id="check">Check Answer</button>
                <p class="feedback"></p>
            </div>
        </div>
    </body>
</html>

Creating event listeners with HTML

<!DOCTYPE html>

<html lang="en">
    <head>
        <link href="https://fonts.googleapis.com/css2?family=Montserrat:wght@500&display=swap" rel="stylesheet">
        <link href="styles.css" rel="stylesheet">
        <title>Trivia!</title>
        <script>
            function checkMultiChoice(event) {

                // Get the element which triggered the event
                let button = event.target;

                // Check if the element's inner HTML matches expected answer
                if (button.innerHTML == '1 person per 6 sheep') {
                    button.style.backgroundColor = 'Green';
                    button.parentElement.querySelector('.feedback').innerHTML = 'Correct!';
                }
                else {
                    button.style.backgroundColor = 'Red';
                    button.parentElement.querySelector('.feedback').innerHTML = 'Incorrect';
                }
            }

            function checkFreeResponse(event) {

                // Get the element which triggered the event
                let button = event.target;

                // Get the input element corresponding to the button
                let input = button.parentElement.querySelector('input');

                // Check for correct answer
                if (input.value === 'Switzerland') {
                    input.style.backgroundColor = 'Green';
                    input.parentElement.querySelector('.feedback').innerHTML = 'Correct!';
                }
                else {
                    input.style.backgroundColor = 'Red';
                    input.parentElement.querySelector('.feedback').innerHTML = 'Incorrect';
                }
            }
        </script>
    </head>
    <body>
        <div class="header">
            <h1>Trivia!</h1>
        </div>

        <div class="container">
            <div class="section">
                <h2>Part 1: Multiple Choice </h2>
                <hr>
                <h3>What is the approximate ratio of people to sheep in New Zealand?</h3>
                <button onclick="checkMultiChoice(event)">6 people per 1 sheep</button>
                <button onclick="checkMultiChoice(event)">3 people per 1 sheep</button>
                <button onclick="checkMultiChoice(event)">1 person per 1 sheep</button>
                <button onclick="checkMultiChoice(event)">1 person per 3 sheep</button>
                <button onclick="checkMultiChoice(event)">1 person per 6 sheep</button>
                <p class="feedback"></p>
            </div>

            <div class="section">
                <h2>Part 2: Free Response</h2>
                <hr>
                <h3>In which country is it illegal to own only one guinea pig, as a lone guinea pig might get lonely?</h3>
                <input type="text"></input>
                <button onclick="checkFreeResponse(event)">Check Answer</button>
                <p class="feedback"></p>
            </div>
        </div>
    </body>
</html>