main.js

const customName = document.getElementById('customname');
const randomize = document.querySelector('.randomize');
const story = document.querySelector('.story');

function randomValueFromArray(array){
  const random = Math.floor(Math.random()*array.length);
  return array[random];
}

let storyText = 'It was 94 fahrenheit outside, so :insertx: went for a walk. When they got to :inserty:, they stared in horror for a few moments, then :insertz:. Bob saw the whole thing, but was not surprised — :insertx: weighs 300 pounds, and it was a hot day.';
let insertX = ['Willy the Goblin', 'Big Daddy', 'Father Christmas'];
let insertY = ['the soup kitchen', 'Disneyland', 'the White House'];
let insertZ = ['spontaneously combusted', 'melted into a puddle on the sidewalk', 'turned into a slug and crawled away'];

randomize.addEventListener('click', result);

function result() {
    let newStory = storyText;
    let xItem = randomValueFromArray(insertX);
    let yItem = randomValueFromArray(insertY);
    let zItem = randomValueFromArray(insertZ);

    newStory = newStory.replace(/:insertx:/g, xItem);
    newStory = newStory.replace(/:inserty:/g, yItem);
    newStory = newStory.replace(/:insertz:/g, zItem);

  if(customName.value !== '') {
    let name = customName.value;
    newStory = newStory.replace(/Bob/g, name);
  }

  if(document.getElementById("uk").checked) {
    let weight = Math.round(300*0.071) + ' stone';
    let temperature =  Math.round((94-32)*(5/9)) + ' centigrade';

    newStory = newStory.replace(/300 pounds/g, weight);
    newStory = newStory.replace(/94 fahrenheit/g, temperature);
    
  }

  story.textContent = newStory;
  story.style.visibility = 'visible';

}