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

Riadh Hamidou
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Riadh Hamidou
Full Stack JavaScript Techdegree Student 3,711 Points
Posted by Riadh Hamidou
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Riadh Hamidou
Full Stack JavaScript Techdegree Student 3,711 Points

Why does (correctGuess = false) not work ?

Hi, I wrote the code like below , but it looks like the correct way to do it is like this (!correctGuess).

What is the difference ?

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 = false)  // This condition doesn't work and it writes the final message to the document after the first guess no matter what the guess is

document.write("<p>It took you " + guessCount + " attempts to guess the number " + randomNumber + ".</p>");
Riadh Hamidou
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.a{fill-rule:evenodd;}techdegree
Riadh Hamidou
Full Stack JavaScript Techdegree Student 3,711 Points
Riadh Hamidou
.a{fill-rule:evenodd;}techdegree
Riadh Hamidou
Full Stack JavaScript Techdegree Student 3,711 Points

And this code works too, Is there big differences between the two methods, is one more preferred than the other ? Sorry, I'm not sure how to embed code 

// This code doesn't use a flag, it compares guess vs randomNumber directly

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("I am thinking of a number between 1 and 10. What is it?");
  guessCount += 1;
} while (parseInt(guess) !== randomNumber)

document.write("<p>It took you " + guessCount + " attempts to guess the number " + randomNumber + ".</p>");

2 Answers

Riadh Hamidou
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.a{fill-rule:evenodd;}techdegree
Riadh Hamidou
Full Stack JavaScript Techdegree Student 3,711 Points
Riadh Hamidou
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Riadh Hamidou
Full Stack JavaScript Techdegree Student 3,711 Points

Yeah, this is why they say javascript turns coffee into code. I needed that coffee.

I read somewhere else that you can't assign in the condition, and despite that, I was staring at it thinking I've done nothing wrong, I just wrote ( ! correctGuess ) in another way. :D

I tried it again and it worked just as fine.

Thank you

Thomas Nilsen
Thomas Nilsen
14,957 Points
Thomas Nilsen
Thomas Nilsen
14,957 Points 
do { 
//rest of code..
} while (correctGuess = false)

You can't assign a variable in the while-part. You have to actually check if it equals some value.

It should look like this:

do { 
//rest of code..
} while (correctGuess === false) //Notice - **not** just one equal-sign
Audra Ogilvy
Audra Ogilvy
3,142 Points
Audra Ogilvy
Audra Ogilvy
3,142 Points

OMG. Thank you, Thomas!!!!! That answer really, really helped.

So, is there a difference between a variable created using the var keyword, and a variable created just with the equals operator? In other words, is this: var guess = false different than this: guess = false ?