獲取錯誤：錯誤：發送後無法設置標題。在重新渲染頁面

Question

我想用nodeJS和firebase構建一個註冊頁面。

當用戶收到註冊錯誤時，頁面將重新加載，並向用戶顯示錯誤。 然後，如果用戶嘗試註冊，他得到了想要的頁面，但我得到：

Error: Can't set headers after they are sent.

幾個小時的研發之後，我覺得我已經明白這個問題。 我的代碼可能已經處於正文或已完成狀態，但某些功能試圖設置標題或狀態碼

有了這些知識，我試圖解決這個錯誤，但我沒有完成。

這裏是我的user.js的（控制器）代碼：

var express = require('express'); 
 
var firebase = require('firebase'); 
 
var router = express.Router(); 
 
var User = require('../models/user'); 
 
var errors; 
 
var errorMessage; 
 

 
/** 
 
sign up 
 
*/ 
 
//sign up page route 
 
router.get('/', function (req, res, next) { 
 
    console.log(errors); 
 
    if (errors) { 
 
    //Handle the errors and show them to the user 
 
    res.render('signUp', {error: true, errorMessage: errorMessage}); 
 
}else { 
 
    res.render('signUp', {title: 'Sign up', user: false, login: true}); 
 
} 
 
}); 
 

 
// sign up request 
 
router.post('/', function(req, res, next){ 
 

 
    console.log(req.body.user.email + ' made a registration request'); 
 
    console.log('Passwword: ' + req.body.user.password); 
 

 
    var email = req.body.user.email; 
 
    var password = req.body.user.password; 
 
    
 
    //reference to the firebase database 
 
    firebase.auth().createUserWithEmailAndPassword(email, password).catch(function(error) { 
 
    if (error) { 
 
     console.log(error.code); 
 
     console.log(error.message); 
 
     errorMessage = error.message; 
 
     errors = true; 
 
     res.redirect('/'); 
 
    } 
 
    }); 
 
    //if user is logged in redirect to homepage 
 
    firebase.auth().onAuthStateChanged(function(user) { 
 
    if (user) { 
 
     res.redirect('/users/home'); 
 
     console.log('User: ' + user.email + ' has logged in'); 
 
    } 
 
    }); 
 
}); 
 

 

 
module.exports = router;

我希望有人能幫助我。

Answer 1

如果您正在使用節點7+版本，你可以使用async/await就像我在下面的代碼片段所做的：

var express = require('express'); 
 
var firebase = require('firebase'); 
 
var router = express.Router(); 
 
var User = require('../models/user'); 
 
var errors; 
 
var errorMessage; 
 

 

 
async function createUser(email, password) { 
 
    return new Promise(resolve => { 
 
    firebase.auth().createUserWithEmailAndPassword(email, password).catch(function(error) { 
 
     if (error) { 
 
     console.log(error.code); 
 
     console.log(error.message); 
 
     errorMessage = error.message; 
 
     errors = true; 
 
     return resolve(true) 
 
     } 
 
     resolve(false) 
 
    }); 
 
    }) 
 
} 
 

 
async function authChange() { 
 
    return new Promise(resolve => { 
 
    firebase.auth().onAuthStateChanged(function(user) { 
 
     if (user) { 
 
     console.log('User: ' + user.email + ' has logged in'); 
 
     return resolve(true) 
 
     } 
 
     resolve(false) 
 
    }); 
 
    }) 
 
} 
 

 

 
// sign up request 
 
router.post('/', async function(req, res, next) { 
 

 
    console.log(req.body.user.email + ' made a registration request'); 
 
    console.log('Passwword: ' + req.body.user.password); 
 

 
    var email = req.body.user.email; 
 
    var password = req.body.user.password; 
 

 
    //reference to the firebase database 
 
    let error = await createUser(email, password) 
 
    if (error) { 
 
    res.redirect('/'); 
 
    } else { 
 
    let logged = await authChange() 
 
    if (logged) { 
 
     res.redirect('/users/home'); 
 
    } 
 
    } 
 
}); 
 

 
module.exports = router;