如何用js给一个DIV一个ID

<div class="class_body">
	<table cellSpacing=0>
		<script language="javascript" type="text/javascript">
			document.write("<tr>");
			titlehaed(0);
			writralldaylong();
			document.write("</tr>");
		</script>
	</table>
</div>
<div class="class_content">
	<table cellSpacing=0 >
		<script language="javascript" type="text/javascript">
			for (j=0;j<24;j++)
			{
				document.write("<tr>");
				titles(j);
				writeTdone(j);
				document.write("</tr><tr>");
				writeTdtwo(j);
				document.write("</tr>");
			}
		</script>
	</table>
</div>
function writeTdone(rowNum)
{
	for(i=0; i<7; i++)
	{
		document.write('<td class="class_td_activity" onclick="clicks('+i + ',' + rowNum +')"></td>');
	}
} 
function writeTdtwo(rowNum)
{
	for(i=0; i<7; i++)
	{
		document.write('<td class="class_td_activityone" onclick="clicks('+i + ',' + rowNum +')"></td>');
	}
} 
function titles(titleNum)
{
	var titleText = new Array("上午12点","上午1点","上午2点","上午3点","上午4点","上午5点","上午6点","上午7点","上午8点","上午9点","上午10点","上午11点","下午12点","下午1点","下午2点","下午3点","下午4点","下午5点","下午6点","下午7点","下午8点","下午9点","下午10点","下午11点");
	document.write('<th rowspan="2" class="class_th_time">'+titleText[titleNum]+'</th>');
}
function sky(z)
{
	z = z+1;
	alert("周" + z);
}
function writralldaylong ()
{
	for(z=0; z<7; z++)
	{
		document.write('<td class="class_td_content"onclick="sky('+z+')"></td>');
	}
}
function titlehaed(titleNum)
{
	var headText = new Array("GMT+08");
	document.write('<th class="class_th_alldaylong">'+headText[titleNum]+'</th>');
}

我是这样做的怎么给他们th里面每个加上不一样的ID呢？
我是用JS写出的一个表格 7天一周那么怎么用JS在这个7个格子里面每个添加一个ID呢?
也是用JS写的请问 用for写出来

---

懒得看你代码 ... 标题的问题回答如下 ...

<div>Hello World</div>
<script type="text/javascript">
var div = document.getElementsByTagName("div")[0];
div.setAttribute("id","yourdiv");

alert( document.getElementById("yourdiv").innerHTML );
</script>

---

这是我根据我对你的意图的猜测得出的结论

function titles(titleNum)
{
        var titleText = new Array("上午12点","上午1点","上午2点","上午3点","上午4点","上午5点","上午6点","上午7点","上午8点","上午9点","上午10点","上午11点","下午12点","下午1点","下午2点","下午3点","下午4点","下午5点","下午6点","下午7点","下午8点","下午9点","下午10点","下午11点");
        document.write('<th rowspan="2" class="class_th_time" id="ID"'+titleNum+'>'+titleText[titleNum]+'</th>');
}