HTML三角函数练习游戏莫名刷新问题求助

我正在开发一款HTML三角函数练习小游戏，但页面总是莫名自动刷新，找不到原因。我怀疑问题出在checkAnswer函数中，相关代码如下：

const sinArray = [
  ['0°', '0', '0'],
  ['30°', 'π/6', '1/2'],
  ['45°', 'π/4', 'r2/2'],
  ['60°', 'π/3', 'r3/2'],
  ['90°', 'π/2', '1'],
  ['120°', '2π/3', 'r3/2'],
  ['135°', '3π/4', 'r2/2'],
  ['150°', '5π/6', '1/2'],
  ['180°', 'π', '0'],
  ['210°', '7π/6', '-1/2'],
  ['225°', '5π/4', '-r2/2'],
  ['240°', '4π/3', '-r3/2'],
  ['270°', '3π/2', '-1'],
  ['300°', '5π/3', '-r3/2'],
  ['315°', '7π/4', '-r2/2'],
  ['330°', '11π/6', '-1/2'],
  ['360°', '2π', 'NAN']
];
var startTime = new Date().getTime() / 1000;
var totalAnswered = 0;
var totalCorrect = 0;
var currentStreak = 0;
var currentAnswer;
var lastQuestion;
var currentScore = 0;
var bestScore = 0;
var timeOfLastCorrect = startTime;
var root = document.querySelector(':root');

function scanCookies() {
  cookie = getCookie("backgroundColor")
  if (!cookie == "") {
    console.log(cookie)
    document.body.style.backgroundColor = cookie;
    var all = document.getElementsByTagName("input")
    for (var i = 0, max = all.length; i < max; i++) {
      all[i].style.backgroundColor = cookie;
    }
  }
  cookie = getCookie("textColor")
  if (!cookie == "") {
    console.log(cookie)
    var all = document.getElementsByTagName("*");

    for (var i = 0, max = all.length; i < max; i++) {
      all[i].style.color = cookie;
    }
  }
  if (!getCookie("bestScore") == "") { bestScore = getCookie("bestScore"); }
}

function setCookie(cname, cvalue) {
  const d = new Date();
  d.setTime(d.getTime() + (10 * 24 * 60 * 60 * 1000));
  let expires = "expires=" + d.toUTCString();
  let cookie = cname + "=" + cvalue + ";" + expires + ";path=/";
  console.log("Cookie set to: " + cookie)
  document.cookie = cookie;
}

function getCookie(cookieName) {
  let name = cookieName + "=";
  let decodedCookie = decodeURIComponent(document.cookie);
  let cookieArray = decodedCookie.split(';');
  console.log(cookieArray);
  for (let i = 0; i < cookieArray.length; i++) {
    let cookieElement = cookieArray[i];
    while (cookieElement.charAt(0) == ' ') {
      cookieElement = cookieElement.substring(1);
    }
    if (cookieElement.indexOf(name) == 0) {
      return cookieElement.substring(name.length);
    }
  }
  console.log("Failed to find cookie " + cookieName);
  return "";
}

function newQuestion() {
  //generate question
  let currentQuestion = getCookie('full_circle_toggle') == 'true' ? Math.floor(Math.random() * 17) : Math.floor(Math.random() * 9);
  let currentSinState = Math.floor(Math.random() * 2)
  //check if qestion is different from last (ignores rad/deg)
  if (currentQuestion + 17 * (currentSinState) == lastQuestion) {
    newQuestion();
    return;
  }
  //choose degree or radian
  let degVsRad = getCookie('degree_toggle') == 'true' ? (getCookie('radian_toggle') == 'true' ? Math.floor(Math.random() * 2) : 0) : 1;
  //actually select question
  let question = currentSinState == 0 ? "Sin (" + sinArray[currentQuestion][degVsRad] + ")" : "Cos (" + sinArray[currentQuestion][degVsRad] + ")";
  //choose matching answer
  currentAnswer = sinArray[(currentQuestion - 4 * currentSinState + 16) % 16][2];
  console.log(currentAnswer);
  //update last question
  lastQuestion = currentQuestion + 17 * (currentSinState);
  //SET QUESTION//
  document.getElementById('question').innerText = question;
}

function checkAnswer() {
  //collect answer
  var userAnswer = document.getElementById("answer").value.toLowerCase().trim();
  //check if answer is an option
  if (isAnswerOption(userAnswer)) {
    //increment total answers
    totalAnswered++;
    //check if answer is right
    if (userAnswer == currentAnswer) {
      //increase counts, update score
      timeOfLastCorrect = new Date().getTime() / 1000;
      currentStreak++;
      totalCorrect++;
      currentScore = totalCorrect * totalCorrect / (timeOfLastCorrect - startTime);
      if (currentScore > bestScore) {
        bestScore = currentScore;
        setCookie("bestScore", bestScore)
      }
      document.getElementById("result").innerText = "Correct! Well done!";
      //updateScore();
      //newQuestion();
    }
    else {
      currentStreak = 0;
      document.getElementById("result").innerText = "Incorrect. Please try again."
    }
  }
  else {
    document.getElementById("result").innerText = "Please enter a valid answer option.";
  }
}

function isAnswerOption(answer) {
  for (x = 0; x < 16; x++) {
    if (sinArray[x][2] == answer) { return true; }
  }
  return false;
}

内容的提问来源于stack exchange，提问作者BurritoKitten