Why does some jquery code only work if it's at the end of my html-body section?

Question

I have the following code for creating tabs. It works at the end of the html body section but not if I place it at the beginning - before all of the divs are defined. Why might that be?

<script type="text/javascript">
    $("ul.tabs li.label").hide();
    $("#tab-set > div").hide();
    $("#tab-set > div").eq(0).show();
  $("ul.tabs a").click(
    function() {
     $("ul.tabs a.selected").removeClass('selected');
     $("#tab-set > div").hide();
     $(""+$(this).attr("href")).show();
     $(this).addClass('selected');
     return false;
    }
  );
  $("#toggle-label").click( function() {
    $(".tabs li.label").toggle();
    return false;
  });
</script>

Answer 1

It is most likely because the DOM is not ready yet, and therefore they don't exist.

Therefore you need to do the following:

$(function() {
    // Any code in here will only be executed when the DOM is ready.
});

Answer 2

you need to wrap it with a document ready block. this prevents the code firing until the page is fully loaded.

<script type="text/javascript">
    $(function() {
      // do something on document ready
      $("ul.tabs li.label").hide();
      $("#tab-set > div").hide();
      $("#tab-set > div").eq(0).show();
      $("ul.tabs a").click(
        function() {
          $("ul.tabs a.selected").removeClass('selected');
          $("#tab-set > div").hide();
          $(""+$(this).attr("href")).show();
          $(this).addClass('selected');
          return false;
        }
      );
      $("#toggle-label").click( function() {
        $(".tabs li.label").toggle();
        return false;
      });
    });
</script>

Answer 3

jQuery(function($) {
    // put your code in here and it will be executed
    // when the document has fully loaded.
});