Shouldnt this give you a number between 0 and 3?

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 = ['mansion', 'apartment', 'shack', 'house'];  // 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 home = document.querySelector('#home');  // This says make a new variable and find the HTML tag that has the ID of "home" 
  var profession = document.querySelector('#profession');
  var pet = document.querySelector('#pet');
  var location = document.querySelector('#location');

  // Fill them with the provided answers
  home.innerText = answers['mash'];
  profession.innerText = answers['profession'];
  pet.innerText = answers['pet'];
  location.innerText = answers['location'];
  home.innerHTML = answers.mash;  // Change the content of the element in the HTML doc with the id "home" to the "mash" value in answers 
  profession.innerHTML = answers.profession;  // Change the content of the element in the HTML doc with the id "career" to the "career" value in answers 
  pet.innerHTML = answers.pet;
  location.innerHTML = answers.location;
}

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 = {
    'mash': mash_choice(),
    'profession': get_answer('profession'),
    'pet': get_answer('pet'),
    'location': get_answer('location')
  }
  // Fill in the answers
  fill_in_answers(answers);

  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