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Editorial Team
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Asked: 2026-05-24T10:08:56+00:00

I’m passing an object of a certain type to an array. When I print

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I’m passing an object of a certain type to an array.
When I print the object from an outside reference I can see all the fields.
When I print the same object from the array reference, I see almost none.

To Explain, here is the code that illustrates the problem:

var test = new OpenLayers.Layer.Vector();

var array = [test];

console.log("******* Printing Test directly ***************");
printObjectProperties(test);

console.log("****** Printing Test from array **************");
for (obj in array){
    printObjectProperties(obj);     
}

The printObjectProperties() function:

function printObjectProperties(eventData) {
        for (var prop in eventData) {
            if (!(typeof (eventData[prop]) == "undefined")) {
                console.log(prop + " = " + eventData[prop]);
            }
        };
}

The complete code (complete html file, you can run and see for youself in the browser console log):
(live example)

<html>
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.3.2/jquery.min.js" type="text/javascript"></script>
<script src="http://www.openlayers.org/api/OpenLayers.js"></script>
<script>

    $(document).ready(function(){

        var test = new OpenLayers.Layer.Vector();

        var array = [test];

        console.log("******* Printing Test directly ***************");
        printObjectProperties(test);

        console.log("****** Printing Test from array **************");
        for (obj in array){
            printObjectProperties(obj);     
        }

    });


function printObjectProperties(eventData) {
        for (var prop in eventData) {
            if (!(typeof (eventData[prop]) == "undefined")) {
                console.log(prop + " = " + eventData[prop]);
            }
        };
}

</script>
</html>
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1 Answer

  1. Editorial Team

    In a for in loop, the first variable (obj) is the key. In an array that’s the index.

    So basically you’re iterating over a number in printObjectProperties. Hence the 0 = 0, because the first index of your array (you have one element) is 0.

    Use this instead:

    printObjectProperties(array[obj]);

    which would evaluate to:

    printObjectProperties(array[0]);

    or:

    printObjectProperties(test);
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