Not really understanding

Hi there,

Given something like this (your code from above):

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 am thinking of a number between 1 and 10. What is it?');
    guessCount+=1;
    if (parseInt(guess) === randomNumber) { 
       correctGuess = true;
     } 
} while(!correctGuess) 

document.write('<h1> You guessed the number!</h1>'); 
document.write ('It took ' + guessCount + ' tries to guess the right number');

I think it might be best to explain with a focus on the correctGuess variable. As you've pointed out, it is set to false at the beginning. Think of this variable as an indication of whether the user has guessed the correct number or not. Since they haven't guessed anything yet, they have not - so, false.

We've generated the number at this point, so we're ready to guess. Enter the do-while loop:

1. The user is asked to guess, and the guess count increases.

   guess = prompt('I am thinking of a number between 1 and 10. What is it?');
   guessCount+=1;
   

2. The guess is compared to the number (randomNumber). If the user guesses correctly, correctGuess would be set to true, indicating that they have guessed the correct number. Otherwise, it stays false because they have not guessed correctly.

   if (parseInt(guess) === randomNumber) { 
      correctGuess = true;
   } 
   

3. The loop checks the while condition - if the condition inside the parentheses matches, it will continue to loop:

   while(!correctGuess) 
   

   It is important to note here that while(!correctGuess) is shorthand for saying "while correctGuess is false" or "while NOT correctGuess". This is the effect of the exclamation point (!) character - it means "not". Since correctGuess is false as long as the user has not guessed the correct answer, we want it to keep asking the user to guess until they get it right. When they do guess correctly, correctGuess is set to true, and the loop breaks.

I can see how this would be confusing - the while loop continues "when the condition is true", but we're looking for a NOT condition... so we're looking for "correctGuess is false" to be "true". It really just means that whatever is in the parentheses has to be a correct statement for the loop to continue - in the parentheses it basically says "correctGuess is false". So, each time through the loop, it checks to see if that is a correct statement - is correctGuess false? If so, it continues.

Does that make sense?

Hi Dave,

Do { prompt } while ( correctGuess) is a shorter way of saying do { prompt } while ( correctGuess === true ).

Do { prompt } while ( ! correctGuess ) is a shorter way of saying do { prompt } while ( correctGuess === false).

As long as correctGuess equals false, we have a ( ! correctGuess ) or ( correctGuess === false ) condition, which means the loop will keep going. As soon as correctGuess equals true, we no longer have a ( ! correctGuess ) or ( correctGuess === false ) condition, so we break out of the loop.

I hope that helps!

Tanya

I also have the same confusion as per Kris. So what I just did was put his code in a markdown. Katie Wood Steven Parker Can you guys help explain this better? I can't quite wrap my head around this one

var randomNumber = getRandomNumber(10);
var guess; 
var guessCount = 0;
var guessCount = 0;
function getRandomNumber( upper ) { 
  return num;
} do 
 guess = prompt('I am thinking of a number between 1 and 10. What is it?');
 guessCount+=1;
 if (parseInt(guess) === randomNumber) { 
 correctGuess = true;
  } 
} while(!correctGuess) 
document.write('<h1> You guessed the number!</h1>'); 
document.write ('it toke ' + guessCount + ' tries to guss the right number');

I now understand. You turned up once again!

I understand why ( ! correctGuess ) works. But why does : (correctGuess = false) not work? Shouldn't it actually work as well?