Question

我是Node.js的新手，我在尝试避免回调地狱时遇到了问题。现在我正在开发一个endpoitn来在mongo数据库中注册用户，我所面临的问题是，如果我将使用它们的函数模块化，我将失去对某些变量的访问。

代码：

工作回调地狱：

    var mongoose = require('mongoose'),
    dbserver = 'mongodb://localhost/',
    dbname = 'authdb';


mongoose.connect(dbserver + dbname);

var db = mongoose.connection;

db.on('error', console.error.bind(console, 'connection error:'));

db.once('open', function callback () {
  console.log('connectet to mongo db: ' + dbname);
})



userModel = require('./user.js');



function singIn (req, res){

    var email = req.body.email,
    name = req.body.name,
    secondName  = req.body.secondName,
    pass = req.body.pass,
    bday = req.body.bday;

    var user = new userModel.user();

    user.Email = email;
    user.Name = name;
    user.SecondName = secondName;
    user.Pass.Hash = pass;
    user.BirthDate = bday;



    db.model('user').find({Email : email},function (err,foundUsers){

    if(!err && foundUsers.length === 0){

        user.save(function (err, users){
    if(err){
        console.log(err);
        res.send("Not inserted");

    }else{
            console.log(user);
            console.log('registered!');
            res.send("OKish");
    }
});
    }else{
        console.log(err);
        console.log(foundUsers);

        res.send("Not inserted");
    }

});

};


exports.singIn  = singIn;

不工作模块化

var mongoose = require('mongoose'),
    dbserver = 'mongodb://localhost/',
    dbname = 'authdb';


mongoose.connect(dbserver + dbname);

var db = mongoose.connection;

db.on('error', console.error.bind(console, 'connection error:'));

db.once('open', function callback () {
  console.log('connectet to mongo db: ' + dbname);
})



userModel = require('./user.js');



function singIn (req, res){

    var email = req.body.email,
    name = req.body.name,
    secondName  = req.body.secondName,
    pass = req.body.pass,
    bday = req.body.bday;

    var user = new userModel.user();

    user.Email = email;
    user.Name = name;
    user.SecondName = secondName;
    user.Pass.Hash = pass;
    user.BirthDate = bday;



    db.model('user').find({Email : email},addUser);

};


function saveUser(err, users){
    if(err){
        console.log(err);
        res.send("Not inserted");

    }else{
            console.log(user);
            console.log('registered!');
            res.send("OKish");
    }
}

function addUser(err,foundUsers){

    if(!err && foundUsers.length === 0){

        user.save(SaveUser);
    }else{
        console.log(err);
        console.log(foundUsers);

        res.send("Not inserted");
    }

}   




exports.singIn  = singIn;

这里的问题是，在第二个片段中，我无法访问函数addUser和saveUser中的变量res和user。

有没有办法让这两个变量都在函数范围内，或者这次我必须承担回调地狱？

谢谢！

Answer 1

您可以在上下文saveUser中定义addUser和signIn函数，以便他们可以访问其参数和局部变量：

function signIn (req, res){    
    var email = req.body.email,
    name = req.body.name,
    secondName  = req.body.secondName,
    pass = req.body.pass,
    bday = req.body.bday;

    var user = new userModel.user();    
    user.Email = email;
    user.Name = name;
    user.SecondName = secondName;
    user.Pass.Hash = pass;
    user.BirthDate = bday;

    db.model('user').find({Email : email},addUser);

    function saveUser(err, users){
        if(err){
            console.log(err);
            res.send("Not inserted");
        }else{
            console.log(user);
            console.log('registered!');
            res.send("OKish");
        }
    }

    function addUser(err,foundUsers){
        if(!err && foundUsers.length === 0){
            user.save(saveUser);
        }else{
            console.log(err);
            console.log(foundUsers);
            res.send("Not inserted");
        }
    }       
};

Answer 2

要么使用回调，要么将任何范围内变量作为额外参数传递。

Answer 3

您可以将第一个参数添加到例如saveUser并将其绑定到res：

function saveUser(res, err, users){
    if(err){
        console.log(err);
        res.send("Not inserted");

    }else{
            console.log(user);
            console.log('registered!');
            res.send("OKish");
    }
}

然后

user.save(saveUser.bind(null,res));

避免回调地狱失去变量范围

3 个答案: