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Asked: 2026-06-06T07:26:26+00:00

I have the following code: <html> <body> <div style=background-color: lightblue; onClick=alert(myArray[0][1])> this is a

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I have the following code:

<html>
<body>
<div style="background-color: lightblue;" onClick="alert(myArray[0][1])">
this is a div
</div>

<script type="text/javascript">
var myArray = new Array();
myArray[0][0] = 0;
myArray[0][1] = 00012;
myArray[0][2] = 00006;
myArray[1][0] = 1;
myArray[1][1] = 00004;
myArray[1][2] = 00001;
</script>
</body>
</html>

When I click on the div, nothing happens; there’s no alert. When I change the inside of alert to a string, such as ‘test’, however, then the alert box does come up.

What am I doing wrong? How can I get the value of an item in a multidimensional array?

Thanks!

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1 Answer

  1. Editorial Team

    The first line of your code:

    var myArray = new Array();

    …will create a new, single dimensional array, myArray, that has no elements. Then when you say:

    myArray[0][0] = 0;

    …you are trying to access a dimension that doesn’t exist yet. That is, myArray[0] is undefined because although myArray is an array it doesn’t have any elements yet – so myArray[0][0] is like saying undefined[0].

    That’s why you have to to assign myArray[0] to refer to a new array before you can access myArray[0][0]. The same thing applies to myArray[1], because JavaScript doesn’t have multi-dimensional arrays per se, it has arrays of arrays. So this is what you need (for a minimal change to your existing code):

    var myArray = [];
myArray[0] = [];
myArray[0][0] =  00012;
myArray[0][1] = 00012;
myArray[0][2] = 00006;
myArray[1] = [];
myArray[1][0] = 1;
myArray[1][1] = 00004;
myArray[1][2] = 00001;

    Note that [] is equivalent to new Array().

    An easier to read and type option is to create the sub-arrays via array literal syntax:

    var myArray = [];
myArray[0] = [00012, 00012, 00006];
myArray[1] = [1, 00004, 00001];

    Or, easiest of all (especially if these are hard-coded values) is creating the whole thing in one statement via a nested array literal (white-space is ignored):

    var myArray = [
                [00012, 00012, 00006],
                [1, 00004, 00001]
              ];

    (Note also that those leading zeros will disappear for numeric data: use strings ("00012" instead of 00012) if you want to retain the zeros.)

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