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    <p><strong>What you're doing</strong></p> <p>It seems like you're misunderstanding the syntax of what you're doing. It is currently equivalent to</p> <pre><code>var dieOne = Math.floor(Math.random() * 6 + 1); var dieTwo = Math.floor(Math.random() * 6 + 1); var foo; foo = dieOne; // a number foo = [foo]; // an array with one number in it foo = foo[dieTwo]; // probably undefined, unlikely case of `dieTwo = 0` // which would give back `dieOne` dice[foo] = dice[foo] + 1; // most likely trying to add 1 to property `undefined` </code></pre> <p>Then later you're doing</p> <pre><code>foo = [1]; // an array length 1 foo = foo[3]; // undefined, it doesn't have an item here foo = dice[foo]; // = dice[undefined] = undefined alert(foo); // alerting "undefined" </code></pre> <hr> <p><strong>What you probably want to be doing</strong></p> <p>It looks like you actually want an <em>Array</em> of <code>6</code> <em>Arrays</em> each of <code>6</code> <em>Numbers</em>; construct your favourite way</p> <pre><code>var dice = [ [0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0] ]; </code></pre> <p>Then for your loop to be </p> <pre><code>var dieOne, dieTwo, i; for(i = 0; i &lt; 30000; ++i) { dieOne = Math.floor(Math.random() * 6); // indices start at 0 and dieTwo = Math.floor(Math.random() * 6); // 6 of them means max is 5 dice[dieOne][dieTwo]++; // count the brackets here.. } </code></pre> <p>then say you want to know how many times you had <em>dieOne = 1, dieTwo = 3</em>, you would look at</p> <pre><code>dice[1][3]; // count the brackets again. </code></pre>
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    1. POIncrementing Multi Dimensional Array in JavaScript
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    1. COI've tried setting all indexes to zero within a loop like so dice[[i][j]] = 0; and it still does not work. Perhaps I am misunderstanding what you mean as "undefined?"
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      1. USJames Manes
    2. COPlease read again where I describe what happens to `foo`. I use `foo` to break your line of code down into a step-by-step of what the interpreter tries to do with your code.
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    3. COHmm.. so in JavaScript I cannot create a 6x6 grid with a two dimensional array, I must make a 6 arrays, each filled with 6 values. Am I understanding this correctly?
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