Code does not run

var randomNumber = getRandomNumber(10);
var guess;
var guessCount = 0;
var correctGuess = false;

function getRandomNumber(upper) {
  var num = Math.floor(Math.random() * upper) + 1; 
  return num;
}

while (guess < 10) {
  guess = prompt("I am thinking of a number between 1 and 10. What is it?");
  guessCount += 1;
  if (parseInt(guess) === randomNumber) {
    correctGuess = true;
    break;
  }  
} 
if (correctGuess) {  
document.write("<h1>You guessed the number!</h1>");
document.write("It took you " + guessCount + " tries to guess the number " + randomNumber);
} else {
  document.write("<h1>Sorry, you did not guess the correct number</h1>");
}