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

Posted by emhes
emhes
6,934 Points

Why doesn't ( guess !== randomNumber) work?

This is what I wrote as the solution before watching Dave's solution.

I don't understand why this wouldn't work:

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 ( guess !== randomNumber)

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

Isn't that saying: DO

  • prompt the user for their answer and store their answer in the 'guess' variable
  • increase the guess count by 1 WHILE
  • if the user's answer is not equal to the Random Number then continue to run the DO loop

What am I missing?

2 Answers

Erick Kusnadi
Erick Kusnadi
21,615 Points
Erick Kusnadi
Erick Kusnadi
21,615 Points

1) there's an extra } 2) there's an infinite loop. randomNumber is an Integer, while guess is a String. When you use the prompt function the input from the user will be a string, so you have to parse guess into a number, you can use the parseInt() function for this. http://www.w3schools.com/jsref/jsref_parseint.asp

Or you can even just change: ( guess !== randomNumber) to ( guess != randomNumber). The second version automatically tries to change the string to a number, while the first version doesnt

emhes
emhes
6,934 Points

ah... that's right. Prompt inputs are considered strings even if a number is entered... That's what I was forgetting. Thank you!

Jared Hensley
Jared Hensley
8,106 Points
Jared Hensley
Jared Hensley
8,106 Points

I used the following solution to solve, slightly different comparison in the while. Seems to be simpler to me but I guess there are multiple ways to do the same thing!

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("Guess a number between 1 and 10?");
  guessCount++;
  if (parseInt(guess) === randomNumber) {
    correctGuess = true;
  }
} while (correctGuess == false)
document.write("<h1>You guessed the number!</h1>");
document.write("It took you " + guessCount + " attempt(s) to guess the number " + randomNumber);