全选框

<script type="text/javascript">  
    // 全选按钮选中标志 
    var checkflag = "false"; 
    // 全选功能 
    function selectAll(name){ 
        var field = document.getElementsByName(name); 
        // 如果全选按钮状态是未选中 
        if (checkflag == "false"){ 
            for (i = 0; i < field.length; i++){ 
                field[i].checked = true; 
            } 
            // 更改全选按钮选中标志 
            checkflag = "true"; 
        }else{ 
            for (i = 0; i < field.length; i++){ 
                field[i].checked = false;  
            } 
            // 更改全选按钮选中标志 
            checkflag = "false"; 
        } 
    } 
 
</script>

-----------------------html-------------------------------

  <thead>
            <tr>
                <th><input type="checkbox" value="全选" onClick="selectAll('userIds')">&nbsp;&nbsp;选择</th>
                <th>登录名</th>
                <th>姓名</th>
            </tr>
        </thead>
        <tbody>
            <c:forEach items="${users}" var="item">
            <tr>
                <td><input id="userId_${item.id}" name="userIds" type="checkbox" value="${item.id}" ></td>
                <td>${item.loginName}</td>
                <td>${item.name}</td>
            </tr>
            </c:forEach>
        </tbody>