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                        /JavaScript進階篇

為什么代碼運行之后沒有一點效果？

<!DOCTYPE html>
<html>
?<head>
? <title> text </title> ?
? <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> ?
? <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 tr=document.getElementsByTagName("tr");
??????? for(var i=0;i<tr.length;i++){
????????? bgChange(tr[i]);
??????? }
?? }

??? function bgChange(obj){
????? obj.onmouseover=function(){
??????? obj.style.backgroundColor="#f2f2f2";
????? }
????? obj.onmouseout=function(){
??????? obj.style.backgroundColor="#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 tr=document.createElement("tr");
????? var th1=document.createElement("th");
????? var th2=document.createElement("th");
????? th1.innerHTML="2015";
????? th2.innerHTML="小楊";
????? var th3=document.createElement("th");
????? th3.innerHTML="無";
????? var tab=document.getElementById("table");
????? tab.appendChild(tr);
????? tr.appendChild(th1);
????? tr.appendChild(th2);
????? tr.appendChild(th3);
????? var tr = document.getElementsByTagName("tr");
????????? for(var i= 0;i<tr.length;i++)
????????? {
????????????? bgChange(tr[i]);
????????? }
???? }
?????? ?
??? ?
???? // 創建刪除函數
???? function delete(obj){
??????? var tr=obj.parentNode.parentNode;
??????? tr.parentNode.removeChild(tr);?????? ?
??????? }

? </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(this)">刪除</a></td>? ?
????????? 
?????? </tr>

?????? <tr>
????????? <td>xh002</td>
????????? <td>劉小芳</td>
????????? <td><a href="javascript:;" onclick="delete(this)">刪除</a></td> ?
????????? 
?????? </tr> ?

???? </table>
???? <input type="button" value="添加一行" onclick="add()"/>? ?
???? 
?</body>
</html>