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Asked: 2026-06-02T20:36:45+00:00

I’m new to JavaScript. I’ve worked my work through Learning JavaScript (o’reilly) but am

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I’m new to JavaScript.
I’ve worked my work through Learning JavaScript (o’reilly) but am just trying to make my first JavaScript.

I thought it best to work on something I’m interested in and as it turned out is fairly complicated.

I’m basically trying to simulate (eventually) a situation in Space Hulk (Boardgame) where a Genestealer has 12 steps between him and the Space Marine.
On the first step its 6 on either dice to kill the Genestealer, and after that 5 or 6 to kill.
The gun jams if the number on the dice is the same.

I’m just trying to emulate the first step here. I think the problem is with jamCheck.

Basically this outputs as always true, even if I change it to != it always shows gun jammed.

I wondered if the variable needed to be passed into another local variable, but it works for killCheck without having to do this. (and I tried it, although I may be doing it wrong)

It is completely possible there is something really simple wrong here.

I hope you can help, or point me in the right direction.

Many thanks!

        <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
        <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en">
        <head>
        <title>SH</title>
        <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
        <script type="text/javascript">
      //<![CDATA[

    function diceRoll1() {
       iValue = Math.random(); // random number between 0 and 1
       iValue *= 6; // multiply by 6 to move the decimal
       iValue = Math.floor(iValue)+1; // round to nearest integer. +1 to 1-6.
       var roll1 = iValue;
       document.getElementById('result1').innerHTML = 'Dice roll 1 : ' + roll1;
       killCheck (roll1);
       jamCheck (roll1);
       return;
    }

    function diceRoll2() {
       iValue = Math.random(); // random number between 0 and 1
       iValue *= 6; // multiply by 6 to move the decimal
       iValue = Math.floor(iValue)+1; // round to nearest integer. +1 to 1-6.
       var roll2 = iValue;
       document.getElementById('result2').innerHTML = 'Dice roll 2 : ' + roll2;
       killCheck (roll2);
       jamCheck (roll2);
       return;  
    }

    function killCheck(roll1,roll2){
        if (roll1==6 || roll2==6)
        {
        document.getElementById('kill').innerHTML = 'GS KILLED';
        }
        return;
    }

    function jamCheck(roll1,roll2){
        if (roll1 == roll2)
        {
        document.getElementById('jam').innerHTML = 'GUN JAMMED';
        }
        return;
    }   

    //]]>
    </script>
    </head>
    <body onload="diceRoll1();diceRoll2();killCheck();jamCheck();">
      <p id="result1">Dice roll 1</p>
      <p id="result2">Dice roll 2</p>
      <p id="kill">GS ALIVE</p>
      <p id="jam">GUN FINE</p>

    </body>
    </html>

EDIT: I eventually got there with a lot of help from a friend; here is the current code:

...
function getDiceValue() {
var diceValue = Math.random(); 
diceValue *= 6;
diceValue = Math.floor(diceValue) + 1; 
return diceValue;
}

function killCheck(roll1, roll2) {
if (roll1 === 6 || roll2 === 6) {
document.getElementById('kill').innerHTML = 'GS KILLED';
}
return;
}

function jamCheck(roll1, roll2){
if (roll1 === roll2) {
document.getElementById('jam').innerHTML = 'GUN JAMMED';
}
return;
}

function rollDice() {
var roll1 = getDiceValue(),
roll2 = getDiceValue();
document.getElementById('result1').innerHTML = 'Dice roll 1 : ' + roll1;
document.getElementById('result2').innerHTML = 'Dice roll 2 : ' + roll2;
killCheck (roll1, roll2);
jamCheck (roll1, roll2);
}
//]]>
...
<body onload="rollDice();">
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1 Answer

  1. Editorial Team

    Math.floor() rounds down (think about the name… ceil rounds up) if you REALLY want to round to the “nearest” integer you need to use Math.round().

    In your case if you multiply by 6 and round down you’ll never get a number higher than 5.

    I suspect this is your problem, though I only glanced at your code, so, forgive me if that’s just one mistake and not the cause of your issue.

    [Edit] upon further reflection, disregard the above. The problem is that your methods expects 2 parameters but you’re only passing in one.

    I think you’re misunderstanding the way parameter passing works.

    jamCheck(p1, p2){} what you name these is not relevant. These labels only exist INSIDE your method. I suspect that what is confusing you is that you’re using the same labels for the variables you’re passing in, as well as the ones in your method. So, when you call the method jamCheck(roll1) it can’t do what it needs to cause it’s designed to work on 2 variables. Beyond that whatever result you’re getting is just the browser trying to make up for code whose syntax is broken. In languages like C or Java you wouldn’t even be able to compile such code; You’d be pointed at these lines as not making any sense, by the compiler.

    So, the solution is (something like)…

    var roll1,roll2;

roll1 = diceRoll1();
roll2 = diceRoll2();
jamCheck(roll1,roll2);
killCheck(roll1,roll2);

    But in your diceRoll methods the last thing you’ll need to do is return roll1; (or roll2 respectively)

    And look to kirean’s answer for how to wrap this all up in an init method, so that you’re not calling 4 (or more) methods from the body’s onload callback.

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