验证用户名是否存在

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在注册的时候,常会进行用户名验证,如果输入的用户名已经存在,立刻给出提示而不是等信息填写完后进行验证,如果输入信息很多的话,不仅信息会丢失,并且会进行一次回传,很恼火,那么注册的时候使用Ajax验证一下,就可以避免这些问题了,下面给出最简单的使用示例,判断用户名是否存在: 第一种:最原始的JS验证 HMTL代码:<html xmlns="http://www.w3.org/1999/xhtml" ><head id="Head1" runat="server">    <title></title>    <script language="javascript" type="text/javascript" src="CheckUserName.js"></script>    <script language="javascript">    </script></head><body>    <form id="form1" runat="server">    <table cellpadding="0" cellspacing="0" width="100%">        <tr>          <td>Ajax Example:</td>        </tr>        <tr>            <td>                <table cellpadding="0" cellspacing="0" width="100%">                  <tr>                    <td>Example 1:Check UserName IsExists</td>                  </tr>                  <tr>                    <td>                        <asp:Label ID="lblUserName" runat="server" Text="用户名："></asp:Label>                        <input id="txtUserName" type="text" onblur="onBlur()"/>                    </td>                  </tr>                </table>            </td>        </tr>    </table>    </form></body></html> //CheckUserName.jsvar ajax = function(option){    var request;    var createRequest = function()    {        var request;        if (window.XMLHttpRequest)        {            request = new XMLHttpRequest();        }        else        {            try            {                request = new ActiveXObject("Microsoft.XMLHTTP");            }            catch (e)            {                request = new ActiveXObject("Msxml2.XMLHTTP");            }        }        return request;    }    var sendRequest = function()    {        request = createRequest();//        request.open("post", option.url, true);//        request.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");//        request.onreadystatechange = ResponseRequest;//        request.send(option.param);        request.open("get", option.url+"?t=0", true);        request.onreadystatechange = ResponseRequest;        request.send(null);        }    var ResponseRequest = function()    {        if (request.readyState == 4)        {            if (request.status == 200)            {                option.Success(request);            }            else            {                option.Failure(request);             }        }    }    sendRequest();}var onBlur = function(){    var option = { url: "Test.aspx", param: "t=1", Success:function(request){alert(request.responseText);}, Faitrue: function(request) { alert(false) } };    new ajax(option);} //Test.aspxprotected void Page_Load(object sender, EventArgs e) {            if (Request["t"] != null)            {                this.Response.Clear();                string t = Request["t"].ToString();                if (t == "1")                {                    Response.Write("用户名已存在，请填写其他的用户名!");                }                else if (t == "0")                {                    Response.Write("该用户名没被注册，可以使用!");                }                this.Response.End();            } }  第二种方式:利用JQuery框架ajax验证 HMTL代码:<html xmlns="http://www.w3.org/1999/xhtml" ><head runat="server">    <title></title>    <script src="jquery-1.2.6.min.js" type="text/javascript"></script>    <script>        $(document).ready(function() {        $("#Button1").click(function() {                $.ajax({                    type: "get",                    url: "ResponsePage.aspx?t=0",                    dataType: 'html',                    success: function(data) {                        alert("post " + data);                    },                    error: function() { alert('error!'); }                });            });        });    </script></head><body>    <form id="form1" runat="server">    <div>        <input id="Button1" type="button" value="显示" />    </div>    </form></body></html>//ResponsePage.apsxprotected void Page_Load(object sender, EventArgs e){            this.Response.Clear();            string t = Request["t"].ToString();            if (t == "1")            {                Response.Write("用户名已存在，请填写其他的用户名!");            }            else if (t == "0")            {                Response.Write("该用户名没被注册，可以使用!");            }            this.Response.End();}
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