function CreateHTTPObject() {
    var xmlhttp;

    try {
        xmlhttp = new ActiveXObject("Msxml2.XMLHTTP");
    }
    catch (e) {
        try {
            xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
        }
        catch (e) {
            xmlhttp = false;
        }
    }

    if (!xmlhttp && typeof XMLHttpRequest != 'undefined') {
        try {
            xmlhttp = new XMLHttpRequest();
        }
        catch (e) {
            xmlhttp = false;
        }
    }

    if (!xmlhttp && window.createRequest) {
        try {
            xmlhttp = window.createRequest();
        }
        catch (e) {
            xmlhttp = false;
        }
    }

    return xmlhttp;
}

function OnReadyStateChng(xmlhttp, v) {
    if (xmlhttp.readyState == 4) {
        if (xmlhttp.status == 200) {
            var ResponseTxt = xmlhttp.responseText;


            switch (v) {
                //检查用户名是否可用 
                case 1:
                    if (ResponseTxt == "1") {
                        document.getElementById("uNameInfo").innerHTML = "恭喜，该用户名还没人使用。";
                    }
                    else {
                        document.getElementById("uNameInfo").innerHTML = "很遗憾，该用户名已有人使用。";
                    }
                    break;
                //检查用户是否登录
                case 2:
                    break;
                //查找图片
                case 3:
                    document.getElementById("iit").src = "/uploads/" + ResponseTxt;
                    break;
                default:
            }



        }
        else {
            alert("HTTP 错误，状态码：" + xmlhttp.status);
        }
    }
}

function SubmitMsg(url, v) {
    var xmlhttp = CreateHTTPObject();
    if (!xmlhttp) {
        return; //无法创建 xmlhttp 对象
    }

    //Ajax 提交
    xmlhttp.open("GET", url, true);
    xmlhttp.onreadystatechange = function() { OnReadyStateChng(xmlhttp, v);  };
    xmlhttp.send(null);
}