Js_Ajax_用户名检测

输入"root"，OK；输入其它，Error

ajax.jsp

    var xhr;

    function createXhr() {

        if (window.XMLHttpRequest) {

            xhr = new XMLHttpRequest();

        } else {

            xhr = new ActiveXObject("Microsoft.XMLHTTP");

        }

    }

    function chk(elm) {

        var name = elm.value;

        createXhr();

        xhr.onreadystatechange = callback;

        xhr.open("get", "AjaxServlet?para="+name, true);

        xhr.send(null);

    }

    function callback() {

        if (xhr.readyState == 4) {

            if (xhr.status == 200) {

                var t = xhr.responseText;

                //文本 --> Json

                var json = eval("(" + t + ")");

                var elmCmt=document.getElementById("cmt")

                if(json.result){

                    elmCmt.innerText="OK";

                }else{

                    elmCmt.innerText="ERR";

                }

            }

        }

    }

<body>

    <input type="text" onblur="chk(this)">

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

    <br>

    <input type="text">

</body>

AjaxServlet.java

    public void doGet(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

            response.setCharacterEncoding("utf-8");

            AhJson aj = new AhJson();

            String para=request.getParameter("para");

            JSONObject jo = new JSONObject();

            if("root".equals(para) ){

                jo.put("result", true);

            }else{

                jo.put("result", false);

            }

            response.getWriter().write(jo.toString());

    }

巴特西

Js_Ajax_用户名检测

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