node.js - 错误 : Can't set headers after they are sent , 仅在刷新页面后发生

Question

每次我在路由“localhost:8080/”刷新 html 页面或登录用户时，我都会收到此错误:发送后无法设置 header 。据我所知发生此问题的原因是回调被意外调用了两次。该应用程序不会崩溃或发生任何事情，它只是在控制台上不断记录相同的错误。

这是代码。

var User        = require('../models/user');
var Story       = require('../models/story');
var jwt         = require('jsonwebtoken');
var config      = require('../../config');


var superSecret = config.secret;


module.exports = function(app, express) {

    // creating our first router
    var apiRouter = express.Router();

    // signup a user

    apiRouter.post('/signup', function(req, res) {

            var user = new User({
                name: req.body.name,
                username: req.body.username,
                password: req.body.password
            });

            user.save(function(err) {
                if(err) res.send(err);
                res.json({ message: 'User has been created!' });
            });
    });

    apiRouter.get('/users', function(req, res) {

        User.find({}, function(err, users) {

            if(err) res.send(err);

            res.json(users);

        });

    });



    // user login

    apiRouter.post('/login', function(req, res) {

        User.findOne({
            username: req.body.username
        }).select('name username password').exec(function(err, user) {

            if(err) throw err;

            if(!user) {
                res.json({ message: "Wrong User" });
            } else if(user) {

                var validPassword = user.comparePassword(req.body.password);

                if(!validPassword) {
                    res.json({ message: "Invalid Password" });

                } else {

                    var token = jwt.sign({
                        id: user._id,
                        name: user.name,
                        username: user.username
                    }, superSecret, {
                        expiresInMinute: 1440
                    });

                    // return all the sucess
                    res.json({
                        success: true,
                        message: "Successfully login and token created!" + token.name,
                        token: token

                    });
                };

            }

        });

    });


    // write a middleware for login
    // A middleware for login user only, once a user has logged in , he can enter other links below
    apiRouter.use(function(req, res, next) {

        // do logging
        console.log("Somebody just came to our app!");

        var token = req.body.token || req.param('token') || req.headers['x-access-token'];

        // check if token exist
        if(token) {

            jwt.verify(token, superSecret, function(err, decoded) {
                if(err) {
                    res.status(403).send({ success: false, message: 'Failed to authenticate user' });
                } else {

                    // if everything is good save request for use in other routes
                    req.decoded = decoded;

                    next(); 
                }
            });

        } else {
            res.status(403).send({ success: false, message: 'No token provided' });
        }
    });


    apiRouter.route('/')

        .post(function(req, res) {

            var story = new Story({
                user: req.decoded.id,
                content: req.body.content
            });

            story.save(function(err, stor) {
                if(err) res.send(err)
                console.log(stor);
                res.json(stor);
            });

        })


        .get(function(req, res) {

            Story.find({ user: req.decoded.id }, function(err, story) {
                if(err) res.send(err);

                res.json(story);
            });


        });




    apiRouter.get('/me', function(req, res) {

        res.send(req.decoded.name);

    });

    apiRouter.route('/:user_id')


        .get(function(req, res) {

            User.findById(req.params.user_id, function(err, user) {
                if(err) res.send(err);

                res.json(user);

            });


        })

        .put(function(req, res) {

            User.findById(req.params.user_id, function(err, user) {

                if(err) res.send(err);

                if(req.body.name) {
                    user.name = req.body.name;
                }

                if(req.body.username) {
                    user.username = req.body.username;

                }

                if(req.body.password) {
                    user.password = req.body.password;
                }

                user.save(function(err) {
                    if(err) res.send(err);

                    res.json({ message: "User updated" });

                });


            });

        });

    return apiRouter;

}

Answer 1

发生错误时您发送了两次响应:

if (err) res.send(err);
res.json(foo);

将其替换为:

if (err) { res.send(err); return; }
res.json(foo);