Question

考虑下面的代码：

userSessionDetail.save((err, data) => {
    if (data) {
        console.log('User Session has been successfully created!');
        returnUserData = {
            username: user.username,
            sessionid: LoginUserModel.findOne({
                    email: req.body._usercredentials.email
                })
                .sort({
                    loginDateTime: 'desc'
                })
                .then((res) => {
                    // console.log(res._id) Successfully get value from promise
                    return res._id
                })
                .catch((err) => {
                    console.log(err);
                })
        }
        console.log(returnUserData.sessionid); //empty
    } else {
        console.log('While creating User Session, something went wrong.');
    }
})

我正在尝试的是从我的承诺中获取价值并将我的财产价值sessionid加入。上面的代码并没有从我的承诺中获得价值。它显示了我的结果：

用户会话已成功创建！承诺{发射器：
EventEmitter { domain：null， _events：{reject：[Function]}， _eventsCount：1， _maxListeners：undefined}，emit：{}，ends：true}

您是否可以澄清如何将生成的'res._id'传递给属性sessionid的值，而不是承诺本身？

Answer 1

mongoose的findone方法返回一个promise，当mongodb（最终）返回数据时执行Promise.then()回调：

userSessionDetail.save((err, data) => {
    if (data) {
        console.log('User Session has been successfully created!');
        LoginUserModel.findOne({
                            email: req.body._usercredentials.email
                        })
                        .sort({
                            loginDateTime: 'desc'
                        })
                        .then((res) => {
                            // console.log(res._id) Successfully get value from promise
                            returnUserData = {
                                username: user.username,
                                sessionid: res._id
                            }
                            console.log(returnUserData.sessionid); //empty
                        })
                        .catch((err) => {
                            console.log(err);
                        })
    } else {
        console.log('While creating User Session, something went wrong.');
    }
})

如何从成功的承诺中获取价值并存储到外部变量中？

1 个答案: