<table id="table">
  <tr><td>行1</td></tr>
  <tr><td>行2</td></tr>
  <tr><td>行3</td></tr>
  <tr><td>行4</td></tr>
 ​<tr><td>行5</td></tr>
</table>

<script>
  $(document).ready(function() {
    $("#table tr:even").addClass("even-row");
  });
</script>