Object Oriented Quiz Project - How to make this reusable

function Quiz() {
  this.questions = [];
}

Quiz.prototype.add = function (question) {
  this.questions.push(question);
}

//Changes quiz progress at bottom of page and question/answers for next question
Quiz.prototype.nextQuestion = function() {
  const progressElement = document.getElementById("progress");
  progressElement.innerHTML = "Question " + questionNumber + " of " + this.questions.length;
  questionDisplay.innerHTML = this.questions[questionNumber -1].question;
  answer1Display.innerHTML = this.questions[questionNumber - 1].wrongAnswer;
  answer2Display.innerHTML = this.questions[questionNumber - 1].correctAnswer;
}


//Function to display user's final score after quiz
Quiz.prototype.scorePage = function() {
  let scoreHTML = "You answered " + correctScore + " out of " + this.questions.length + " correct!";
  questionDisplay.innerHTML = scoreHTML;
  answer1Display.innerHTML = "";
  answer2Display.innerHTML = "";
  wrongAnswerButton.style.display = "none";
  correctAnswerButton.style.display = "none";
}

Quiz.prototype.isEnd = function() {
  if(questionNumber <= this.questions.length) {
    this.nextQuestion();
  } else {
    this.scorePage();
  }
}

//Starting score is 0. Keeps track of which question user is on with questionNumber

let correctScore = 0;
let questionNumber = 1;

//Displays question on page
const questionDisplay = document.getElementById("question");

//Displays wrong answer as first option
const answer1Display = document.getElementById("choice0");
const wrongAnswerButton = document.getElementById("guess0");

//Displays correct answer as second option
const answer2Display = document.getElementById("choice1");
const correctAnswerButton = document.getElementById("guess1");


function userGuess (isCorrect) {
  if(isCorrect) {
    correctScore++;
    alert("That is correct!");
    questionNumber++;
  } else {
    alert("Sorry that is incorrect");
    questionNumber++;
  }
}

correctAnswerButton.onclick = function () {
  userGuess("correct");
}
wrongAnswerButton.onclick = function () {
  userGuess();
}