关于JS改变值的问题(菜鸟)

<script language="JavaScript">
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if(obj.style.display=="")
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obj1.innerHTML="开启";
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obj1.innerHTML="关闭";
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<body>
<div id="n1" style="display:;">
<table>
<tr>
<td>1</td>
</tr>
</table>
</div><div id="n2" onclick="show(n1,n2)">关闭</div><div>
<table id="n3">
<tr>
<td>4</td>
</tr>
</table>
</div></body>
</html>