pvjq,
<table>
<tbody>
<tr>
<td><span id="1">Тут кусок тек...<span id="2">Тут кусок текста</span></span></td>
</tr>
</tbody>
</table>
<script>
var one = document.querySelector("[id='1']"),two = document.querySelector("[id='2']");
one.firstChild.data = "12345";
two.firstChild.data = "67890";
</script>