The initialized Javascript array solely consists of undefined elements, without any of the expected values

I was under the impression that I knew how to declare JavaScript arrays, but in this particular script, I seem to be stuck in an infinite loop of undefined elements within the array.

In my code, I define three arrays containing numbers—two with multiple values and one with a single value.

There's a switch statement that assigns one of these arrays to a new variable called cluster_array.

However, when I try to iterate through cluster_array using a for loop, I encounter an endless loop where all elements are undefined. What could I possibly be overlooking?

<script type="text/javascript">
    var ga_west_cluster = new Array(10,11,12,14,74,75,76,77,78,79,80,81,82,83,85,86,87,88,89,90,91,92,295,296);

// original problematic array
    var ga_east_cluster = new Array(84);
// solved by adding an extra (dummy) value   
    var ga_east_cluster = new Array(1,84);
    var sc_cluster      = new Array(93,94,95,96,97,98,99,100,101,102,103);
</script>

The following is the content of the alert:

var test_message        = "cluster data\n";
    for(var k=0;k<cluster_array.length;k++)
        test_message    += "value: "+cluster_array[k]+"\n";

Answer №1

Using the "Array()" constructor to initialize arrays is not recommended. Instead, it's better to use the array constant notation like this:

var myarray = [value, value, value, ... ];

The single-argument form of the "Array()" constructor can be misinterpreted as a request to create an array with that many empty values, which serves little purpose. In general, it's safer and more efficient to stick with the array constant notation for initializing arrays.

Although modern browsers have improved in this regard, there was a time when some browsers would allocate memory for the single-argument constructor, posing a potential risk if a very large number was accidentally passed in.

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