Node JS蓝鸟承诺

Question

I am creating promises with node JS. But i have the idea that i still have a callback hell going on...

That is because i need results from my first callback, in the third callback.

I already tried it with bluebird, but i have some confusion about this.

Can anyone give me some sample code how i can write this out nicely? See the following example: https://gist.github.com/ermst4r/8b29bf8b63d74f639521e04c4481dabb

Answer 1

Use async / await to avoid nested promises.

You could refactor your code to something like this

async function doSomething(){
    try {
        const user = await UserProfileMatch.getNewUser(item.fk_user_id)
        await ActiveAuctionProfile.closeActiveAuctionProfile(item.aap_id)

        if(user.length  > 0 ) {
            const is_active = await ActiveAuctionProfile.isProfileActive(user[0].profile_id)

            const number_of_profiles = await = UserProfileMatch.countActiveProfilesForUser(item.fk_user_id)

            if(is_active.result === 0 && number_of_profiles < config.settings.lovingbids_start_profile) {

                await UserProfileMatch.updateProfileMatch(item.fk_user_id, user[0].profile_id,1,false)

                await ActiveAuctionProfile.createNewActiveProfile({
                    fk_auction_profile_id:user[0].profile_id,
                    start_date:moment().format("YYYY-MM-DD HH:mm:ss") ,
                    expire_date:moment().add(config.settings.increment_settings,'seconds').format("YYYY-MM-DD HH:mm:ss")
                })

                ExpireProfileRegister.removeExpireResult(item.id);
                page++;
                next();

            } else {
                console.log("exists");
                ExpireProfileRegister.removeExpireResult(item.id);
                page++;
                next();
            }

        } else {
            console.log("niet");
            page++;
            next();
        }

    }catch(err){
       console.log("One of the promises failed:", err)
    }
}

Note that we declare the wrapping function with async and that instead of nesting the callbacks, we use await to tell the async function to wait for this function to finish before running the next line of code.

Also note that all the await functions are wrapped in a try / catch block to catch any errors. This is instead of using the .catch() notation.

Read more about async functions here

Answer 2

I couldn't debug but something along these lines should give you a refactored code using promises correctly.

UserProfileMatch.getNewUser(item.fk_user_id)
                .then(user => ActiveAuctionProfile.closeActiveAuctionProfile(item.aap_id))
                .then(() => user.length  > 0 ? ActiveAuctionProfile.isProfileActive(user[0].profile_id)
                                             : (console.log("niet"), page++, next()))
                .then(is_active => [UserProfileMatch.countActiveProfilesForUser(item.fk_user_id), is_active.result])
                .then(([number_of_profiles,n]) => n === 0 &&
                                                  number_of_profiles < config.settings.lovingbids_start_profile ? UserProfileMatch.updateProfileMatch(item.fk_user_id, user[0].profile_id,1,false))
                                                                                                                : (console.log("exists"),
                                                                                                                   ExpireProfileRegister.removeExpireResult(item.id),
                                                                                                                   page++,
                                                                                                                   next());
                .then(() => ActiveAuctionProfile.createNewActiveProfile({ fk_auction_profile_id: user[0].profile_id,
                                                                          start_date           : moment().format("YYYY-MM-DD HH:mm:ss") ,
                                                                          expire_date          : moment().add(config.settings.increment_settings,'seconds').format("YYYY-MM-DD HH:mm:ss")
                                                                        })
                .then(() => (ExpireProfileRegister.removeExpireResult(item.id), page++, next()));

Please note that at the 3rd then stage i returned an array like

[UserProfileMatch.countActiveProfilesForUser(item.fk_user_id), is_active.result]

which carries the is_active.result to the next then stage, at where we collect it as n through array destructuring.

Answer 3

Nice thanks all for your feedback. I read about async and async.series seems to be the best way for me. It keeps my code structured. See ....

                            var get_user;
                            var user_active;
                            var user_profile;
                            async.series([

                                // check for the new user
                                function checkForNewUser(callback)
                                {
                                    UserProfileMatch.getNewUser(item.fk_user_id).then(function (user) {
                                        get_user = user;
                                        callback(null,user);

                                    });
                                },
                                // close the profile
                                function closeProfile(callback)
                                {
                                    ActiveAuctionProfile.closeActiveAuctionProfile(item.aap_id).then(function () {
                                        if (get_user.length > 0) {
                                            ActiveAuctionProfile.isProfileActive(get_user[0].profile_id).then(function (is_active) {
                                                user_active = is_active.result;
                                                callback(null,user_active);
                                            });
                                        } else {
                                            callback(null,false);
                                        }

                                    });

                                },

                                // count the active profiles
                                function countActiveProfiles (callback) {

                                    UserProfileMatch.countActiveProfilesForUser(item.fk_user_id).then(function (number_of_profiles) {
                                        user_profile = number_of_profiles;
                                        callback(null,user_profile);
                                    });
                                },

                                // decide when we want to create an user
                                function determineCreation(callback) {

                                    if(user_active === 0 && user_active === 0) {
                                        UserProfileMatch.updateProfileMatch(item.fk_user_id, get_user[0].profile_id, 1, false).then(function () {
                                            ActiveAuctionProfile.createNewActiveProfile({
                                                fk_auction_profile_id: get_user[0].profile_id,
                                                start_date: moment().format("YYYY-MM-DD HH:mm:ss"),
                                                expire_date: moment().add(config.settings.increment_settings, 'seconds').format("YYYY-MM-DD HH:mm:ss")
                                            }).then(function () {
                                                ExpireProfileRegister.removeExpireResult(item.id);
                                                callback(null,true);
                                            });

                                        });
                                    } else {
                                        ExpireProfileRegister.removeExpireResult(item.id);
                                        callback(null,true);
                                    }
                                }

                            ], function(err,res) {
                                // after done, go to the next page
                                page++;
                                next();
                            });