Javascript Node.js-从MySQL查询返回值

我想返回Node.js中的MySQL查询，但是我遇到了一些问题

问题1。”var userInfo'无法从函数'Authenticate（）'获取值

问题2。抛出将被“dbclient.query”捕获，而不是您可以看到的我的代码

希望大家能帮我

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SearchUser=function（电子邮件、回调）{
dbclient.query（“从用户中选择*，其中电子邮件=\”“+电子邮件+\”，函数（错误，结果）{
if（err | | results.length身份验证方法无法同步。您应该使用异步方法。请尝试此操作

app.post('/create_member_check', function(req, res) {
    var Authenticate = function (req, callback) {
        SearchUser(req.body.email, function (isExist) { 
            if (isExist === true)
                return callback(101);
            else if (req.body.email === undefined || req.body.email == "")
                return callback(102);
            else if (req.body.password === undefined || req.body.password == "")
                return callback(103);
            else if (isExist === undefined)
                return callback(104);

            var user = {
                "email": req.body.email,
                "password": req.body.password
            };
            AddUser(user); //this is maybe asynchronous, again
            callback(null, user);
        });
    }

    Authenticate(req, function(err, user){
        var userInfo;
        if (err == 101)
            userInfo = "[Error] This account already exists.";
        else if (err == 102)
            userInfo = "[Error] Please key in 'email'.";
        else if (err == 103)
            userInfo = "[Error] Please key in 'password'.";
        else if (err == 104)
            userInfo = "[Fatal Error] SearchUser return 'undefined'.";

        res.render("login_system/create_member_check", {
            layout: false,
            pagename: "create",
            authenticate: userInfo
        });
    });
});

读一下；）
谢谢！！太棒了：）
SearchUser = function (email, callback) {
    dbclient.query("SELECT * FROM user WHERE email = \"" + email + "\"", function (err, results) {
        if (err || results.length <= 0)
            callback(false);
        else
            callback(true);
    });
}

app.post('/create_member_check', function(req, res) {
    var Authenticate = function (req, callback) {
        SearchUser(req.body.email, function (isExist) { 
            if (isExist === true)
                return callback(101);
            else if (req.body.email === undefined || req.body.email == "")
                return callback(102);
            else if (req.body.password === undefined || req.body.password == "")
                return callback(103);
            else if (isExist === undefined)
                return callback(104);

            var user = {
                "email": req.body.email,
                "password": req.body.password
            };
            AddUser(user); //this is maybe asynchronous, again
            callback(null, user);
        });
    }

    Authenticate(req, function(err, user){
        var userInfo;
        if (err == 101)
            userInfo = "[Error] This account already exists.";
        else if (err == 102)
            userInfo = "[Error] Please key in 'email'.";
        else if (err == 103)
            userInfo = "[Error] Please key in 'password'.";
        else if (err == 104)
            userInfo = "[Fatal Error] SearchUser return 'undefined'.";

        res.render("login_system/create_member_check", {
            layout: false,
            pagename: "create",
            authenticate: userInfo
        });
    });
});