<script type="text/javascript">

    function checknickname(){

        //①    抓取被校验的用户名信息

        var nickname = document.getElementById("usernickname").value;

        nickname = encodeURIComponent(nickname);//特殊字符处理

        var ajaxObj = new XMLHttpRequest();

        ajaxObj.onreadystatechange = function(){

            if(ajaxObj.readyState==4){

                document.getElementById('check').innerHTML = ajaxObj.responseText;

            }

        }

        //②ajax抓取到用户名的昵称传递给服务器

        ajaxObj.open('GET','/thinkajax/index.php/Home/Index/checknicname?nickname=' + nickname);

        ajaxObj.send(null);

    }

</script>

<table align="center" border="0">

            <tr>

                <td>姓名：</td>

                <td><input type="text" name="username"/></td>

            </tr>

            <tr>

                <td>昵称：</td>

                <td>

                    <input type="text" name="usernickname" id="usernickname" onblur="checknickname()"/>

                    <span id="check" style="color:red"></span>

                </td>

            </tr>

            <tr>

                <td colspan="2" align="center"><input type="submit" value="提交"/></td>

            </tr>

        </table>

/*

     *用户昵称校验

    */

    public function checknicname($nickname){

        echo $nickname;

        $info = D('user')->where("usernickname='$nickname'")->find();

        if($info){

            echo "用户名已经存在，请换一个吧";

        }else{

            echo "用户名正常使用！！";

        }

        exit;

    }