避免回調地獄丟失變量範圍

Question

我是新來的Node.js，我有問題試圖拒絕回調地獄。 現在我正在開發一個在mongo數據庫中註冊用戶的endpoitn，我遇到的問題是，如果我在使用它們的地方對模塊化函數進行模塊化，則會失去對某些變量的訪問權限。

代碼：

工作回調地獄：

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; 

不在這裏工作模塊化

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; 

的問題是，在第二個片段，我不能存取權限變量資源和用戶在函數addUser和saveUser中。

有沒有辦法讓這兩個變量在函數的範圍內，或者我必須忍受這次的回調地獄？

謝謝！

Answer 1

可以上下文signIn中定義的saveUser和addUser功能，使他們可以訪問其參數和局部變量：

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

要麼回調，要麼傳入任何範圍內的變量作爲額外的參數。

Answer 3

您可以添加第一個參數，例如saveUser並將其綁定到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"); 
    } 
} 

然後

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