Garbage values in JavaScript?

/* Is there such a thing as garbage values in JavaScript?

Am reading that in C, if you define a variable without initializing it to a specific value, that variable may in fact have a garbage value stored inside it. I noticed that in the apps.js program, the instructor indicated that the condition in the while loop is checked before executing. Does that imply that there is no essence of garbage value in JS? */


var upper = 10000;
var randomNumber = getRandomNumber(upper);
var guess;
var attempts = 0;

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

while (guess !== randomNumber)
{
  guess = getRandomNumber(upper);
  attempts++;
}
document.write("<p>The random number was: " + randomNumber + "</p>");
document.write("<p>It took the computer " + attempts + " attempts to get it right.</p>");