Random Number Generation

JavaScript
1

I am using

Math.floor(Math.random() * high) + low;

to generate a random number. I thought this will generate a random value between the high value and low value. But when I use it in the below program the number generated is sometimes greater than the high value. Can someone please tell me why?

<html>
<head>
<title>The Number Guessing Game</title>
<script>
//Dipin
//The Number Guessing Game
//The computer will the guess the number that the use thinks

     var guess = 0;
     var reply = "";
     var msg = "";
     var high = 100;
     var low = 1;
    
     msg =  "Please think of a number between 1 and 100. \

";
msg += "I will try to guess the number you thought.
";
msg += "If the number I guess is too high please reply with a ‘h’.
";
msg += "If the number I guess is too low please reply with a ‘l’.
";
msg += "If I guess correctly please reply with a ‘c’.
";
alert(msg);

     while(reply != 'c'){
        guess = Math.floor(Math.random() * high) + low;

        alert("low: "+low); //testing statement
        alert("high: "+high); //testing statement
        //alert("guess: "+guess); //testing statement

        msg =  "My guess is: "+guess+". \

";
msg += “Please reply with h=high/l=low/c=correct.
“;
reply = prompt(msg,””);

        if(reply == 'h'){
           high = guess;
        } //too high condition 
        if(reply == 'l'){
           low = guess;
        } //too low condition 
        if(reply == 'c'){
           alert("Hooray!!! I am the greatest guesser.");
        } //correct guess condition
     } //end while loop
  &lt;/script&gt;

</head>
<body>
<center>
<h2>The Number Guessing Game</h2>
</center>
<hr>
<h3>Please refresh the page to play the game again.</h3>
</body>
</html>

1 Like
2

If you want it to include high as one of the values then simply use

var range = high - low + 1;

3

Notice that the code gives a number from low to high but not including high. For example, if low is 1 and high is 10, it will give random whole numbers from 1 to 9 inclusive. 10 is not included.

4

Thank you. That seems to work perfectly.

5 
var range = high - low;
var rndnum = Math.floor(Math.random() * range) + low;