js代码获值问题

<table border="1"> <TR> <TD id="zoom" class="F311" height="20" vAlign="top" width="100%" align="left"> 测试数据 </TD> </TR> </table>
请问怎么用JS代码获得“测试数据”这几个值????
<table border="1"> <TR> <TD id="zoom" class="F311" height="20" vAlign="top" width="100%" align="left"> 测试数据 </TD> </TR> </table>
document.getElementById('zoom').innerHTML