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                        /JavaScript進(jìn)階篇

為什么代碼運(yùn)行之后沒有一點(diǎn)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(biāo)移動(dòng)改變背景,可以通過給每行綁定鼠標(biāo)移上事件和鼠標(biāo)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(gè)函數(shù)，供添加按鈕調(diào)用，動(dòng)態(tài)在表格的最后一行添加子節(jié)點(diǎn)；
???? 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(chuàng)建刪除函數(shù)
???? 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(xué)號(hào)</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>