document.getElementById(id).style.display="none";為隱藏

//document.getElementById("test1").style.display="block";//顯示

document.getElementById(id).style.display="";為顯示

程式碼例項

<table width="100%" class="resbutton">
<tr>
<td align="left" width="33%">

<input type="button" name="DataMaintenance" class="button"
value="新增" onclick="add()" id="news"/>

<input type="button" name="DataMaintenance" class="button"
value="修改" onclick="modify()" id="test1" />
</td>
</tr>
</table>
<script Language="Javascript1.2">
if(table1.rows.length==0){
//alert("aaa");
    document.getElementById("test1").style.display="none";//隱藏

document.getElementById("test1").style.display="";//顯示

}else{
//alert("bbb");
    document.getElementById("news").style.display="none";
}

</script>