jQueryテーブル間の合計行数の取得

<table>
  <tr id="parent_1">
    <td>Parent 1</td>
  </tr>
  <tr class="child">
    <td>Child 1</td>
  </tr>
  <tr class="child">
    <td>Child 2</td>
  </tr>
  ...
  <tr id="parent_2">
    <td>Parent2</td>
  </tr>
  ...
</table>

var childCount = ($('#parent_2').get(0).rowIndex - $('#parent_1').get(0).rowIndex) - 1;

$('#parent_1 ~ .child:not(#parent_2 ~ *)').size();

var rowid1 = 'parent_1';
var rowid2 = 'parent_2';

var rows = $("#"+rowid1).parent().find('tr');
var count = 0;

for (var i = 0; i < rows.size(); i++) {
    var el = rows.get(i);

    // Done counting
    if (el.id == rowid2) break;

    if (el.id != rowid1) {
        ++count;
    }
}

alert("There are " + count + " rows between");