Will this code work every time or will there be an error at some point in the code?

Dave's code looks a bit different than mine. So I want to make sure that this code will work every single time as well. I have tested it myself and it does work, but I want to make sure no error will happen in the code.

CODE:

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

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

do {

guess = prompt('Please guess a number between 1 and 10');

guessCount +=1;

}while(parseInt(guess) !== randomNumber)

document.write('It took you ' + guessCount + ' tries to guess the correct number ' + randomNumber);