Wrong random number

Question

ok, I made my code a bit more complicated than it strictly  needed to be for the challenge, but I had already made almost exactly this program to challenge myself earlier in the course.  I made the program to prompt the user for a lower and upper value. Then have the program adjust the number of guesses allowed to get the number based on how big a gap there is between the values.  
I have 2 problems, one that i had before this challenge and one that only came up when i added in the user picking the lower value instead of it just being 1.
When i set the program to prompt for a lower value too, the math seems to be off.   For testing i was putting in 50 and 100 for the lower and upper values, but i was regularly getting random numbers smaller than 50.
The problem that i had from the beginning was if the number of possible guesses was over 1k, the program just stops.  My code is below.
/*
Random number guessing game.
The user can select a number and the game
Will generate a random number from 1 to the number selected.
The user has a different number of chances to guess the number 
depending on how large a number selected
*/
// Prompt user to pick how high the random number will go and generate the random number
alert('Pick 2 numbers, and I will pick a random number between them for you to guess');
var lower = prompt("Pick a number");
var upper = prompt("Pick a larger number");
var range = upper - lower;
var randomNumber = Math.floor(Math.random()* (upper- lower + 1 )) + 1;
var guesses = 0;
var guessed = false;
// dermine the number of guesses allowed by how large a number the user picks.
function numberOfGuesses (range) {
    if (range <= 10) {
        guesses = 3 ;   
    } else if (range <= 100) {
        guesses = 8;
    } else if (range <= 1000) {
        guesses = 15;
    }else {
        guesses = math.ceil(math.log2(range));
    }
    return guesses;
}
// compare the guess to the random number generated.
function main (guesses) {
    for (i = guesses; i > 0; i--) {
        var guess = prompt('I am thinking of a number between ' + lower + ' and ' + upper + '. What is it? You can guess ' + guesses + 'time(s)');
        if (parseInt(guess) === randomNumber){
            guessed = true;
            break;
        } else if (guess < randomNumber) {
            alert('Your guess was too low, try again!');
            guesses -= 1;
        } else {
            alert('Your guess was too high, try again!');
            guesses -= 1;
        }
    }
    if (guessed === true) {
        alert('You guessed it! My Number was' + randomNumber + '!');
    } else {
        alert('Betetr luck next time! My Number was ' + randomNumber + '!');
    }
}
numberOfGuesses(range);
main(guesses);

Steven Parker · Answer

I don't know why the amount would make a difference, but I'm guessing your calculations sometimes become string concatenations.  Some things I noticed are:
Remember that prompt returns a string.  To be safe, convert it to a number right away.
To make your range fully adjustable, multiply by one more than your range, and then add the lower value.
JavaScript is case-sensitive, so "Math" must have a capital "M".
(I learned something myself .. I thought you were going to need ln(range)/ln(2) .. but look, there's a log2!)
Some suggestions:
make sure there are spaces where literal strings concatenate with variables
fold alert text into prompts so the computer waits on the person and not vice-versa
add validity checking (and re-tries) on inputs
don't say "try again" right before "game over"
And a code snippet:
```js
var lower = parseInt(prompt("Pick 2 numbers, and I will pick a random number between them for you to guess"
                            + "

First, pick the Smaller number"));
var upper = parseInt(prompt("Now, pick the Larger number"));
var range = upper - lower;
var randomNumber = Math.floor(Math.random() * (range + 1)) + lower;
var guesses = numberOfGuesses(range);
var guessed = false;
// dermine the number of guesses allowed by how large a number the user picks.
function numberOfGuesses(range) {
  return Math.ceil(Math.log2(range + 1));
}
```
Happy coding!

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Wrong random number

Christopher Borchardt

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Christopher Borchardt

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1 Answer

Steven Parker

Steven Parker

Christopher Borchardt

Christopher Borchardt