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JavaScript JavaScript Loops, Arrays and Objects Simplify Repetitive Tasks with Loops `do ... while` Loops

Posted by john larson
john larson
16,594 Points

I can't see why my counter variable is returning NaN

function GRN(upper){
    var number = Math.floor(Math.random() * 10) + 1;
    return number;
}

var RN = GRN(10);
console.log(RN)
var guess;
var counter;

do {
    guess = prompt("Pick a number 1-10");
    guess= parseInt(guess);
    counter += 1;
} while (guess !== RN)
print(guess + " is the number <br> " + counter + " tries.");

The code seems to work fine except for the counter .

1 Answer

David Bath
David Bath
25,940 Points
David Bath
David Bath
25,940 Points

You aren't initializing the value of counter, so it is undefined. You can't increment "undefined", so you end up with NaN. When you declare the counter variable set it to 0.

john larson
john larson
16,594 Points

oh yea... silly me.