Question

<table>
  <tr class="codesgroupheader"><td>Header1</td></tr>
  <tr><td>1</td></tr>
  <tr class="codesgroupheader"><td>Header2</td></tr>
  <tr><td>2</td></tr>
  <tr class="codesgroupheader"><td>Header3</td></tr>
  <tr><td>3</td></tr>
  <tr class="codesgroupheader"><td>Header4</td></tr>
</table>

And here is the jQuery code

$('.codesgroupheader').not(':last').each(function() {
   alert($(this).nextUntil('.codesgroupheader').find('tr').size());
});

But It always returns me zero..

Answer 1

Your code does the following:

$(this)                        // <tr>           <-- = this
.nextUntil('.codesgroupheader')// All elements between this and <tr class="...">
.find('tr')                    // Seeks for a <tr> inside <tr> - Not found

If you want to select the number of <tr> elements with the given class, use:

alert($('tr.codesgroupheader').not(':last').length);

If you want to get the number of <tr>s between the current and next <tr class=...>, use:

// this = any <tr>
$(this).nextUntil(".codesgroupheader", "tr").length;

For additional reference and usage of the nextUntil function, see the jQuery documentation.