[英]foreach async function in node.js
我想遍歷每個學生,然后執行兩個查詢,這兩個查詢的執行應同步,首先是第一個,然后是第二個查詢,因為這取決於第一個。
我已經寫了一些代碼,但似乎根本不起作用:
Student.find({ status: 'student' })
.populate('student')
.exec(function (err, students) {
if (err) {
return res.status(400).send({
message: errorHandler.getErrorMessage(err)
});
}
_.forEach(students, function (student) {
async.waterfall(
[
function (callback) {
console.log('first ' + student.firstName);
Student.find({ "_id": student.id }, callback);
},
function (student, callback) {
console.log('second '+ student[0].firstName);
WorksnapsTimeEntry.find({
"student": {
"$in": student.map(function (el) {
return el._id
})
}
}, callback);
}
],
function (err, results) {
if (err) {
// do something
} else {
// results are the matching entries
console.log('third');
var totalMinutes = 0;
var totalAvgLevelActivity = 0;
var counter = 0;
_.forEach(results, function (item) {
_.forEach(item.timeEntries, function (item) {
if (item.duration_in_minutes) {
totalMinutes = totalMinutes + parseFloat(item.duration_in_minutes[0]);
}
if (item.activity_level) {
totalAvgLevelActivity = totalAvgLevelActivity + parseFloat(item.activity_level[0]);
counter++;
}
});
});
var obj = {};
obj.studentId = 'test';
obj.firstName = 'test';
obj.lastName = 'test';
obj.municipality = 'test';
obj.totalMinutes = totalMinutes;
obj.totalAvgLevelActivity = totalAvgLevelActivity / counter;
arrayReports.push(obj);
// console.log('not yet finished.');
}
}
);
});
res.json(arrayReports);
console.log('finished.');
任何人都知道如何在Node.js中實現這一目標
mongoose
是應許的,您不必使用async
來處理流,也不必使用lodash來實現簡單的forEach。 並且您通過_id請求查找是無用的,您已經有一個Student
對象:
Student.find({ status: 'student' })
// .populate('student') // why this?
.then(function (students) {
// build an array of promises
var promises = students.map(function (student) {
return WorksnapsTimeEntry.find({
"student": student._id;
});
});
// return a promise to continue the chain
return Promise.all(promises);
}).then(function(results) {
// results are the matching entries
console.log('third');
var totalMinutes = 0;
var totalAvgLevelActivity = 0;
var counter = 0;
_.forEach(results, function (item) {
_.forEach(item.timeEntries, function (item) {
if (item.duration_in_minutes) {
totalMinutes = totalMinutes + parseFloat(item.duration_in_minutes[0]);
}
if (item.activity_level) {
totalAvgLevelActivity = totalAvgLevelActivity + parseFloat(item.activity_level[0]);
counter++;
}
});
});
var obj = {};
obj.studentId = 'test';
obj.firstName = 'test';
obj.lastName = 'test';
obj.municipality = 'test';
obj.totalMinutes = totalMinutes;
obj.totalAvgLevelActivity = totalAvgLevelActivity / counter;
arrayReports.push(obj);
// console.log('not yet finished.');
res.json(arrayReports);
console.log('finished.');
}).catch(function(err) {
return res.status(400).send({
message: errorHandler.getErrorMessage(err)
});
});
聲明:本站的技術帖子網頁,遵循CC BY-SA 4.0協議,如果您需要轉載,請注明本站網址或者原文地址。任何問題請咨詢:yoyou2525@163.com.