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

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

    if(document.getElementById("uk").checked) {
        let weight = Math.round(300*0.071429) + ' stone'
        let temperature =  Math.round((94 -32)*5/9) + ' centigrade';
        newStory = newStory.replace(/94 fahrenheit/gi, temperature);
        newStory = newStory.replace(/300 pounds/gi, weight);
    }

    

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