JavaScript DOM方法表格添加删除

<!DOCTYPE HTML>
<html>
<head>
<meta charset="utf-8">
<title>表格添加删除</title>
<script>
window.onload=function ()
{
   var oTab=document.getElementById('tab1');
   
   var oBtn=document.getElementById('btn1');
   var oName=document.getElementById('name');
   var oAge=document.getElementById('age');
   var id=oTab.tBodies[0].rows.length+1;
   
   oBtn.onclick=function ()
   {
      var oTr=document.createElement('tr');
      
      var oTd=document.createElement('td');
      oTd.innerHTML=id++;    //记录id,避免有行被删除,id发生重复
      oTr.appendChild(oTd);
      
      var oTd=document.createElement('td');
      oTd.innerHTML=oName.value;
      oTr.appendChild(oTd);
      
      var oTd=document.createElement('td');
      oTd.innerHTML=oAge.value;
      oTr.appendChild(oTd);
      
      var oTd=document.createElement('td');
      oTd.innerHTML='<a href="javascript:;">删除</a>';
      oTr.appendChild(oTd);
      
      oTd.getElementsByTagName('a')[0].onclick=function ()
      {
         oTab.tBodies[0].removeChild(this.parentNode.parentNode);
      };
      
      oTab.tBodies[0].appendChild(oTr);
   };
};
</script>
</head>

<body>
姓名:<input  type="text" />
年龄:<input  type="text" />
<input  type="button" value="添加" />
<table   width="500">
   <thead>
       <td>ID</td>
       <td>姓名</td>
       <td>年龄</td>
        <td>操作</td>
    </thead>
    <tbody>
       <tr>
           <td>1</td>
           <td>Blue</td>
           <td>27</td>
           <td></td>
        </tr>
       <tr>
           <td>2</td>
           <td>张三</td>
           <td>23</td>
           <td></td>
        </tr>
       <tr>
           <td>3</td>
           <td>李四</td>
           <td>28</td>
           <td></td>
        </tr>
       <tr>
           <td>4</td>
           <td>王五</td>
           <td>25</td>
           <td></td>
        </tr>
       <tr>
           <td>5</td>
           <td>张伟</td>
           <td>24</td>
           <td></td>
        </tr>
    </tbody>
</table>
</body>
</html>