js调用dom对象

<table>
 <tr class="even"   onclick="doClick(this);" onmouseover="this.className=‘highlight‘"  onmouseout="this.className=‘even‘" >
  <td width="20">10</td>
  <td width="20" >10</td>
  <td width="40" >
      <span id="ss" >6</span>
    </td>
  <td width="120" >6</td>
 </tr>
</table>
<div id="div1">abc</div>

</body>
<script>
function doClick(e){
var id=e.getElementsByTagName(‘span‘)[0].id;
alter(id);
window.location="#";
}
</script>
</html>