问题遇到的现象和发生背景
用代码块功能插入代码，请勿粘贴截图
```javascript
<%@ page language="java" contentType="text/html; charset=utf-8"
pageEncoding="utf-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>表格的添加和删除</title>
</head>
<script>
window.onload=function(){
function del(object){
var table=object.parentNode.parentNode.parentNode;
var tr=object.parentNode.parentNode;
table.removeChild(tr);
}
}
</script>
<body>
<%!
public class Teacher{
int id;
String name;
String brithday;
String address;
double salary;
String operate;
public Teacher(int id,String name,String brithday,String address,double salary,String operate){
this.id=id;
this.name=name;
this.brithday=brithday;
this.address=address;
this.salary=salary;
this.operate=operate;
}
int getId()
{
return id;
}
String getName()
{
return name;
}
String getBrithday()
{
return brithday;
}
String getAddress()
{
return address;
}
double getSalary()
{
return salary;
}
String getOperate()
{
return operate;
}
}
%>
<%
Teacher[] teacher=new Teacher[10];
teacher[0]=new Teacher(11201,"文华","1980-6-12","淮南",6600,"英语");
teacher[1]=new Teacher(11202,"余祥","1984-7-23","合肥",7000,"数据结构");
teacher[2]=new Teacher(11203,"于资","1985-2-1","南京",6700,"离散");
teacher[3]=new Teacher(11204,"卜悦","1991-5-16","合肥",6600,"高等数学");
teacher[4]=new Teacher(11205,"王毅","1987-7-16","芜湖",6600,"线性代数");
teacher[5]=new Teacher(11206,"赵鑫","1988-3-26","合肥",6600,"java");
teacher[6]=new Teacher(11207,"丁莹","1990-11-21","蚌埠",6600,"c++");
teacher[7]=new Teacher(11208,"程明","1984-12-17","合肥",6600,"c语言");
teacher[8]=new Teacher(11209,"张强","1986-9-16","阜阳",6600,"毛概");
teacher[9]=new Teacher(11210,"周霞","1991-5-26","合肥",6600,"思修");
%>
<table align="center" border="2" width="70%">
<tr>
<th>教工号</th><th>姓名</th><th>出生日期</th><th>籍贯</th><th>薪水</th><th>课程</th><th>操作</th>
</tr>
<%
int i;
for(i=0;i<teacher.length;i++){%>
<tr>
<td align="center"><%=teacher[i].getId() %></td>
<td align="center"><%=teacher[i].getName() %></td>
<td align="center"><%=teacher[i].getBrithday() %></td>
<td align="center"><%=teacher[i].getAddress() %></td>
<td align="center"><%=teacher[i].getSalary() %></td>
<td align="center"><%=teacher[i].getOperate() %></td>
<td align="center"><a href="javascript:void(0);" onclick="del(this)">删除</a>
<a href="#">修改</a>
</td>
<%}%>
</table>
</body>
</html>
运行结果及报错内容
写个了删除的触发事件但是没有反应是怎么回事
