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                        /JavaScript進階篇

請大神幫忙看下代碼哪里有錯誤為什么出不來效果謝謝

<!DOCTYPE?html>
<html>
?<head>
??<title>?new?document?</title>??
??<meta?http-equiv="Content-Type"?content="text/html;?charset=gbk"/>???
??<script?type="text/javascript">?
??
??????window.onload?=?function(){
??????????????????
?????//?鼠標移動改變背景,可以通過給每行綁定鼠標移上事件和鼠標移除事件來改變所在行背景色。
????????var?aTr=document.getElementsByTagName('tr');
????????for(var?i=1;i<aTr.length;i++)
????????{
????????????aTr[i].onmouseover=function()
????????????{
????????????????this.style.background='#f2f2f2';
????????????}
????????????aTr[i].onmouseout=function()
????????????{
????????????????this.style.background='#fff';
????????????}
????????}
????????
	?}
?????
??????//?編寫一個函數，供添加按鈕調用，動態在表格的最后一行添加子節點；
??????function?add()
??????{
??????????var?oTab=document.getElementById('table');
??????????var?aTr=document.getElementsByTagName('tr');
??????????
??????????var?oTr=document.createElement("tr");
??????????
??????????var?oTd=document.createElement("td");
??????????oTd.innerHTML="xh00"+(aTr.length+1);
??????????oTr.appendChild(oTd);
???????
??????????var?oTd=document.createElement("td");
??????????oTd.innerHTML=""；
??????????oTr.appendChild(oTd);
??????????
??????????var?oTd=document.createElement("td");
??????????oTd.innerHTML='<a?href="javascript:;">刪除</a>'；
??????????oTr.appendChild(oTd);
??????}
????		
???	?
?????//?創建刪除函數
?????function?delete()
?????{
?????????var?oTab=document.getElementById('table');
?????????var?del=oTab.removeChild(this.parentNode.parentNode);
?????}


??</script>?
?</head>?
?<body>?
	???<table?border="1"?width="50%"?id="table">
	???<tr>
		<th>學號</th>
		<th>姓名</th>
		<th>操作</th>
	???</tr>??

	???<tr>
		<td>xh001</td>
		<td>王小明</td>
		<td><a?href="javascript:;"?onclick="delete()"?>刪除</a></td>???<!--在刪除按鈕上添加點擊事件??-->
	???</tr>

	???<tr>
		<td>xh002</td>
		<td>劉小芳</td>
		<td><a?href="javascript:;"?onclick="delete()"?>刪除</a></td>???<!--在刪除按鈕上添加點擊事件??-->
	???</tr>??

	???</table>
	???<input?type="button"?value="添加一行"?onclick="add()"?/>???<!--在添加按鈕上添加點擊事件??-->
?</body>
</html>