I have a javascript function for process event when DropdownList value changed and it is working fine. This function is call other function like get HTML element ID by passing HTML element as parameter. Then I try to call it when page load / page rendering, HTML element being arrayed.

Example:

<script type="text/javascript">
  function A (obj)
  {
    var value = function B (obj);
  }
  
  function B (obj)
  {
    var idLength = obj.id.length;
    var value = obj.id.lastIndexOf("-");
  }
</script>

When I debugging javascript, I see that obj is array, then I must call it obj[0].id (obj.id is undefined). Why it can be ?