JavaScript MASH Game Will Not Work

function random_number(num) {  // New function called random_choice that takes one parameter, num (or a number)
    // Get a random number between 0 and a passed-in number
    var num = num || 4  // If no number passed in, default to 4
    return Math.floor(Math.random() * num); // Round the answer down (floor) of a random number between 0 and 1 and multiply it by a number. Then return a value and exit the function.
}

function mash_choice() {  // New function called mash_choice that doesn't take any parameters 
    // Since MASH is a special case, give it its own list
    var mash = ['sword', 'mace', 'axe', 'staff'];  // The array of choices to pick from 
    var randomNum = random_number(4);  // Use the above function to get a number between 0 and 4
    return mash[randomNum];  // Return the list item the random number function just picked and exit the function 
}

function get_answer(category) { 
    // Get a random answer from the available answers in a given category
    var choices = [];  // A blank array to hold the user provided answer  
    var selector = 'input[name="' + category + '[]"]';  // Build a CSS selector for the blanks in our passed in category 
    var inputs = document.querySelectorAll(selector);  // Get all of the inputs that match our selector 
    var answer;  

    for (var i = 0; i < inputs.length; i++) {  // Begin a for loop that will run through the code. i++ = add one to the counter which is "i"
        answer = inputs[i].value;  // Get the input with the index value of the counter and get the value ie. if they typed in dog, you get back "dog" 
        if (answer !== '') {  // If answer doesn't equal a blank... !== means doesn't equal 
            choices.push(answer); //...add it to the end of the list 
        }
    }
    return choices[random_number(choices.length)];   // Pick and return a random choice choice.length = number of answers the user provided in that category 
}

function fill_in_answers(answers) {
    // Find the spans that need filled
    var weapon = document.querySelector('#weapon');  // This says make a new variable and find the HTML tag that has the ID of "weapon" 
    var race = document.querySelector('#race');
    var class = document.querySelector('#class');
    var bg = document.querySelector('#bg');

    // Fill them with the provided answers
    weapon.innerText = answers['mash'];
    race.innerText = answers['race'];
    class.innerText = answers['class'];
    bg.innerText = answers['bg'];
    weapon.innerHTML = answers.mash;  // Change the content of the element in the HTML doc with the id "weapon" to the "mash" value in answers 
    race.innerHTML = answers.race;  // Change the content of the element in the HTML doc with the id "career" to the "career" value in answers 
    class.innerHTML = answers.class;
    bg.innerHTML = answers.bg;
}

function handle_submission(evt) {
    evt.preventDefault();  // Stop the form from reloading the page 
    evt.stopPropagation();  // Stop the form from reloading the page

    // Build up our answers object
    var answers_object = {
        'mash': mash_choice(),
        'race': get_answer('race'),
        'class': get_answer('class'),
        'bg': get_answer('bg')
    }
    // Fill in the answers
    fill_in_answers(answers_object);

    var answer_div = document.querySelector('#answers');
    answer_div.classList.add('show');
}

// Find the form on the page and attach a handler for when it's submitted
var form = document.querySelector('#mash');  
form.addEventListener('submit', handle_submission);  // Anytime the form is submitted, we want to call the function handle_submission