如何使此代码以适当的顺序执行

Question

我正在使用 mongodb 在 node.js 中编写一个 Web 应用程序。我有这段代码，但不幸的是它没有按顺序执行，我的意思是 for 循环的迭代速度比那些 db 函数的执行速度要快，这不会造成混乱。

hospitalsCollection.update({}, {$pull: {doctors: parseInt(id)}}, function(err, success) {
    treatmentsCollection.update({}, {$pull: {doctors: parseInt(id)}}, function(err, success) {
        hospitalsCollection.find({"_id": {$in: hospitalsIds}}).toArray(function(err, hospitalsList) {
            for(i = 0; i < hospitalsList.length; i++) {
                for(j = 0; j < hospitalsList[i].treatments.length; j++) {
                    var exists = false;
                    for(k = 0; k < hospitalsList[i].doctors.length; k++) {
                        doctorsCollection.find({"_id": parseInt(hospitalsList[i].doctors[k])}).toArray(function(err, doctorObj) {
                            for(l = 0 ; l < doctorObj.treatments.length; l++) {
                                if(doctorObj.treatments[l] == hospitalsList[i].treatments[j]) {
                                    exists = true;
                                    break;
                                }
                            }
                        });
                        if(exists)
                            break;
                    }
                    if(exists) {
                        break;
                    }
                    else {
                        hospitalsCollection.update({"_id": parseInt(hospitalsList[i]._id)}, {$pull: {treatments: parseInt(hospitalsList[i].treatments[j])}}, function(err, success) {
                            treatmentsCollection.update({"_id": parseInt(hospitalsList[i].teratments[j])}, {$pull: {hospitals: parseInt(hospitalsList[i]._id)}}, function(err, success) {
                                console.log(err);
                            });
                        });
                    }
                }
            }

            for(i = 0; i < treatments.length; i++) {
                doctorsCollection.aggregate([ {$project:{"treatments._id":1, "treatments.price":1}}, {$unwind:"$treatments"},{$match:{"treatments._id": parseInt(treatments[i])}}, {$sort:{"treatments.price":-1}}, {$limit:1} ], function(err, result) {
                    doctorsCollection.aggregate([ {$project:{"treatments._id":1, "treatments.price":1}}, {$unwind:"$treatments"},{$match:{"treatments._id": parseInt(treatments[i])}}, {$sort:{"treatments.price":1}}, {$limit:1} ], function(err, result2) {
                        var maxPrice = result[0].treatments.price;
                        var minPrice = result2[0].treatments.price;
                        treatmentsCollection.update({"_id": parseInt(treatments[i])}, {$set: {"maxPrice": parseInt(maxPrice)}}, function(err, success) {
                            treatmentsCollection.update({"_id": parseInt(treatments[i])}, {$set: {"minPrice": parseInt(minPrice)}}, function(err, success) {
                                console.log(err);
                            });
                        });
                    });
                });
            }
        });
    });
});

我真的不知道该如何处理。任何帮助将不胜感激。谢谢。

Answer 1

使用 Promise（bluebird 很棒）。并重构你的代码。

使用 Promise，您可以执行以下操作。

dbUpdate1()
.then(function(resultFromUpdate1) {

    let multipleUpdates = []
    multipleUpdates.push(updateCollectionA())
    multipleUpdates.push(updateCollectionB())

    return Promise.all(multipleUpdates)

.spread(afterUpdatingBothCollection)


function updateCollectionA(argument) {
    // body...
}

function updateCollectionB(argument) {
    // body...
}

function afterUpdatingBothCollection(resultFrom1, resultFrom2) {
    // body...
}