do...while code won't execute

The following code won't execute properly in either the Firefox or Chrome browser. The prompt box appears and allows for a number entry, but there is no response as it never selects the correct number (even when testing a number from 1 to 3).

Two things I've noticed - in Firefox, the tab is always transferring data. It never seems to fully load. And in Chrome, it completely crashes the moment I prevent it from "creating any additional dialogues".

Also, in JSLint I get the following warning: "document.write can be a form of eval.". I'm not sure if this is throwing things off, as I am new to the DOM and how it operates.

Would anyone have an idea of the issue?

Thanks!

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;
}

do {
  guess = prompt("I'm thinking of a number between 1 & 10.  What is it?");
  guessCount += 1;
  if (parseInt(guess) === randomNumber) {
    correctGuess = true;
  }
} while( ! correctGuess )


document.write("<p>You guessed the correct number: " + getRandomNumber + "</p>");
document.write("<p>It took you " + guessCount + " tries to guess my number</p>");