if both td data are same then merze how in javascript
<table>
<tr>hi</tr>
<tr>
<td>fish</td>
<td>salmon</td>
</tr>
<tr>
<td>fish</td>
<td>cod</td>
</tr>
<tr>
<td>fish</td>
<td>plaice</td>
</tr>
<tr>
<td>bird</td>
<td>robin</td>
</tr>
<tr>
<td>bird</td>
<td>crow</td>
</tr>
</table>