Not able to get attribute value on picker callback function from custom JSP page.

Hi All, I'm stuck on a problem where im not able to get the custom attribute on the picker callback, the tags and the scripts written in the jsp page is as specified below.

Tag written in the jsp page.

<wctags:itemPicker
id="pickerID"
objectType="WCTYPE|wt.doc.WTDocument|Type1|Type2"
componentId="pickerID"
searchResultsViewId="pickerID.view"
label="Submitter"
pickerTitle="Picker Title"
pickerCallback="PickerCallback1"
pickedAttributes="number,attrInternalName1,attrInternalName2,attrInternalName3"
/>

<script>
function PickerCallback1(objects,pickerID)
{
var myJSONObjects = objects.pickedObject;
for (var i = 0; i < myJSONObjects.length; i++) {
var str = JSON.stringify(myJSONObjects[i]);
alert(str);
var fullName = myJSONObjects[i]["attrInternalName1"];
alert(fullName);
}
}

</script>

Output on alert : "undefined"

@HelesicPetr @BjoernRueegg