在Node.js中处理CORS

Question

I have two applications, both running on different instances of Node server, but on the same machine.

The server's server.js :

app.use(function(req, res, next) {
    res.setHeader('Access-Control-Allow-Origin', '*');
    res.setHeader('Access-Control-Allow-Methods', 'GET, POST', 'OPTIONS');
    res.setHeader('Access-Control-Allow-Headers', 'X-Requested-With,content-type, Authorization');

    // intercept OPTIONS method
    if ('OPTIONS' == req.method) {
        console.log('Inside options');
      res.send(200);
    }
    else {
        console.log('Inside others');
      next();
    }
});

app.post('/signin', function(req, res) {
    console.log('signin called');
    User.findOne({email: req.body.email, password: req.body.password}, function(err, user) {
        if (err) {
            console.log('err');
            res.json({
                type: false,
                data: "Error occured: " + err
            });
        } else {
            if (user) {
                console.log('User exists');
                res.json({
                    type: false,
                    data: "User already exists!"
                });
            } else {
                console.log('inside create user');
                var userModel = new User();
                userModel.email = req.body.email;
                userModel.password = req.body.password;
                userModel.save(function(err, user) {
                    user.token = jwt.sign(user, process.env.JWT_SECRET);
                    user.save(function(err, user1) {
                        res.json({
                            type: true,
                            data: user1,
                            token: user1.token
                        });
                    });
                })
                console.log('create user ends');
            }
        }
    });
});

On the client, controller.js :

    $scope.signup = function() {
                var formData = {
                    email: $scope.email,
                    password: $scope.password
                }

                Main.save(formData, function(res) {
                    console.log('response received from service');
                    if (res.type == false) {
                        alert(res.data)
                    } else {
                        $localStorage.token = res.data.token;
                        window.location = "/"    
                    }
                }, function() {
                    $rootScope.error = 'Failed to signup';
                })
            };

And services:

    return {
                save: function(data, success, error) {
                    console.log('signin request sent');
                    $http.post(baseUrl + '/signin', data).success(success).error(error)
                    console.log('signin response received');
                },
                signin: function(data, success, error) {
                    $http.post(baseUrl + '/authenticate', data).success(success).error(error)
                },
                me: function(success, error) {
                    $http.get(baseUrl + '/me').success(success).error(error)
                },
                logout: function(success) {
                    changeUser({});
                    delete $localStorage.token;
                    success();
                }
            };

When I call the signup method from client, server console prints this:

Inside options
OPTIONS /signin 200 12.110 ms - 3
Inside others
signin called
inside create user
create user ends
POST /signin - - ms - -
Inside others
signin called
User exists
POST /signin 200 15.309 ms - 44

What is happening that browser first sends the OPTIONS request, which is responded with a 200 status code, then a POST request is sent which creates the user but client doesn't get the response. Another POST request with the same data is sent by the browser but by then user is already created and server returns a user already exists message.

I am not able to find the reason for it.

Edit: I don't think it's due to CORS at all. I used cars package, and added a app.use(cos()) at the top in server.js. After that the server console prints -

signing called inside create user create user ends POST /signin - - ms - - signing called User exists POST /signin 200 32.007 ms - 44

I think something is getting stuck at server end, and therefore client is sending the request again.

Answer 1

有些防火墙会部分阻止CORS，最佳做法是通过https使用CORS

Answer 2

I guess the problem is with the header. Please add following header while making the POST call :

'Content-Type': 'application/x-www-form-urlencoded;charset=UTF-8'

I have had the similar problem once and it just worked out after adding this header in the POST call.

Hope this works :)