这段代码对表格内容排序 为啥没效果


<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>无标题文档</title><script>
//用于sort排序的比较函数
function compareTrs(tr1,tr2){
var value1 = tr1.cells[3].innerHTML;
var value2 = tr2.cells[3].innerHTML;
return value1.localeCompare(value2);
}
//对表格进行排序
function sortTable(tableID){
var table = document.getElementById(tableID);
var tbody = table.tBodies(0);
var tr = tbody.rows;

var trValue = new Array();
for(var i=0;i<tr.length;i++)
trValue[i] = tr[i];

trValue.sort(compareTrs);//进行排序

var fragment = document.creatDocumentFragment();

for(var i=0;i<tr.length;i++)
fragment.appendChild(trValue[i]);

tbody.appendChild(fragment);
}</script>
</head><body>
<table summary="user infomation table" id="tableSort"> 
<thead>
     <tr>
         <th>会员ID</th>
            <th>会员名</th>
            <th>邮箱</th>
            <th style="cursor:pointer;" onclick="sortTable(tableSort); ">会员组</th>
            <th>城市</th>
            <th>注册时间</th>
        </tr>
    </thead>
    <tbody>
     <tr>
         <td>126</td>
            <td>text001</td>
            <td>[email protected]</td>
            <td>普通会员</td>
            <td>北京</td>
            <td>2011-01-02</td>
        </tr>
        <tr>
         <td>136</td>
            <td>认为二位二</td>
            <td>[email protected]</td>
            <td>中级会员</td>
            <td>合肥</td>
            <td>2011-01-02</td>
        </tr>
        <tr>
         <td>126</td>
            <td>text001</td>
            <td>[email protected]</td>
            <td>普通会员</td>
            <td>南昌</td>
            <td>2011-01-02</td>
        </tr>
        <tr>
         <td>126</td>
            <td>text001</td>
            <td>[email protected]</td>
            <td>中级会员</td>
            <td>北京</td>
            <td>2011-01-02</td>
        </tr>
        <tr>
         <td>126</td>
            <td>text001</td>
            <td>[email protected]</td>
            <td>中级会员</td>
            <td>武汉</td>
            <td>2011-01-02</td>
        </tr>
        <tr>
         <td>126</td>
            <td>text001</td>
            <td>[email protected]</td>
            <td>中级会员</td>
            <td>武汉</td>
            <td>2011-01-02</td>
        </tr>
        <tr>
         <td>126</td>
            <td>text001</td>
            <td>[email protected]</td>
            <td>高级会员</td>
            <td>北京</td>
            <td>2011-01-02</td>
        </tr>
    </tbody>
</table>
</body>
</html>
求大神解释下