Develop Reference

How do I add new field in existing JSON

I have JSON with 10000 unique records and I need to add another field with a unique value to every record. How do I add that?
[
{
_id: "5fffd08e62575323d40fca6f",
wardName: "CIC",
region: "ABC",
location: "AAA",
specialism: "CSR",
__v: 0
},
.
.
.
]
The JSON is stored in variable showWard. How do I add an action field in my JSON with value = './wardName' where wardName is already a field in my JSON?
This is my current code:
app.get('/wards', function (req, res) {
Ward.find({}, function (err, showWard) {
if (err) { console.log(err); return; }
return res.send(showWard);
});
});

Using a .map()? I don't know the logic for determinate the gender, but in Ward.find() callback you can add a thing like that:
app.get('/wards', function (req, res) {
Ward.find({}, function (err, showWard) {
if (err) { console.log(err); return; }
const newShowWard = showWard.map(ward => {
ward.gender = "BOH";
return ward;
})
return res.send(newShowWard);
});
});

Using Multiple FindOne in Mongodb

I am trying to extend the amount of fields that our API is returning. Right now the API is returning the student info by using find, as well as adding some information of the projects by getting the student info and using findOne to get the info about the project that the student is currently registered to.
I am trying to add some information about the course by using the same logic that I used to get the project information.
So I used the same findOne function that I was using for Projects and my logic is the following.
I created a variable where I can save the courseID and then I will put the contents of that variable in the temp object that sending in a json file.
If I comment out the what I added, the code works perfectly and it returns all the students that I require. However, when I make the additional findOne to get information about the course, it stops returning anything but "{}"
I am going to put a comment on the lines of code that I added, to make it easier to find.
Any sort of help will be highly appreciated!
User.find({
isEnrolled: true,
course: {
$ne: null
}
},
'email pantherID firstName lastName project course',
function(err, users) {
console.log("err, users", err, users);
if (err) {
return res.send(err);
} else if (users) {
var userPromises = [];
users.map(function(user) {
userPromises.push(new Promise(function(resolve, reject) {
///////// Added Code START///////
var courseID;
Course.findOne({
fullName: user.course
}, function(err, course) {
console.log("err, course", err, course);
if (err) {
reject('')
}
courseID = course ? course._id : null
//console.log(tempObj)
resolve(tempObj)
}),
///// ADDED CODE END //////
Project.findOne({
title: user.project
}, function(err, proj) {
console.log("err, proj", err, proj);
if (err) {
reject('')
}
//Course ID, Semester, Semester ID
//map to custom object for MJ
var tempObj = {
email: user.email,
id: user.pantherID,
firstName: user.firstName,
lastName: user.lastName,
middle: null,
valid: true,
projectTitle: user.project,
projectId: proj ? proj._id : null,
course: user.course,
courseId: courseID
}
//console.log(tempObj)
resolve(tempObj)
})
}))
})
//async wait and set
Promise.all(userPromises).then(function(results) {
res.json(results)
}).catch(function(err) {
res.send(err)
})
}
})

using promise could be bit tedious, try using async, this is how i would have done it.
// Make sure User, Course & Project models are required.
const async = require('async');
let getUsers = (cb) => {
Users.find({
isEnrolled: true,
course: {
$ne: null
}
}, 'email pantherID firstName lastName project course', (err, users) => {
if (!err) {
cb(null, users);
} else {
cb(err);
}
});
};
let findCourse = (users, cb) => {
async.each(users, (user, ecb) => {
Project.findOne({title: user.project})
.exec((err, project) => {
if (!err) {
users[users.indexOf(user)].projectId = project._id;
ecb();
} else {
ecb(err);
}
});
}, (err) => {
if (!err) {
cb(null, users);
} else {
cb(err);
}
});
};
let findProject = (users, cb) => {
async.each(users, (user, ecb) => {
Course.findOne({fullName: user.course})
.exec((err, course) => {
if (!err) {
users[users.indexOf(user)].courseId = course._id;
ecb();
} else {
ecb(err);
}
});
}, (err) => {
if (!err) {
cb(null, users);
} else {
cb(err);
}
});
};
// This part of the code belongs at the route scope
async.waterfall([
getUsers,
findCourse,
findProject
], (err, result) => {
if (!err) {
res.send(result);
} else {
return res.send(err);
}
});
Hope this gives better insight on how you could go about with multiple IO transactions on the same request.

Error pushing objects into another object in mongodb

req.body.courses has multiples id's of courses that I want to add to a specific categorie, the problem is that when my code runs it save a course more that one time, sometimes four or five times, depending on the number of loops it does.
The function:
router.post('/categories/:cat_id/', function (req, res) {
Categorie.findById(req.params.cat_id, function(err, categorie){
if(err){
console.log(err);
} else {
var courses = req.body.courses;
courses.forEach(function (course){
Course.findOne({ _id: course }, function(err, foundCourse) {
if(err){
console.log(err);
} else {
categorie.courses.push(foundCourse._id);
categorie.save();
}
});
});
}
});
return res.redirect('/dash');
});
The CategorieSchema:
var categorieSchema = mongoose.Schema({
name: String,
courses: [
{
type: mongoose.Schema.Types.ObjectId,
ref: "Course"
}
]
});
Here is an example of trying to add 4 courses to the categorie:
{ "_id" : ObjectId("5a871964a6b4820ecf7abaa7"), "courses" : [ ObjectId("5a870a7374486e0b0d69f710"), ObjectId("5a870a7a74486e0b0d69f711"), ObjectId("5a870a6974486e0b0d69f70f"),
ObjectId("5a870a7374486e0b0d69f710"), ObjectId("5a870a7a74486e0b0d69f711"), ObjectId("5a870a6974486e0b0d69f70f"),
ObjectId("5a870a7374486e0b0d69f710"), ObjectId("5a870a7a74486e0b0d69f711"), ObjectId("5a870a6974486e0b0d69f70f") ], "name" : "test2", "__v" : 3 }

Node.js Is async, It does not wait for the loop to execute completely and each time you are adding _id in existing array because of that adds 2-3 times.
Try this once I have not tested this.
const findOne = (course) => {
return new Promise((resolve, reject) => {
Course.findOne({
_id: course
}, (err, foundCourse) => {
if (err)
return reject(err);
return resolve(foundCourse._id);
});
});
}
router.post('/categories/:cat_id/', function (req, res) {
Categorie.findById(req.params.cat_id, function (err, categorie) {
if (err) {
console.log(err);
res.status(400).json(err);
} else {
var courses = req.body.courses;
Promise.all(courses.map((course) => {
return findOne(course);
})).then((data) => {
// check if course id already there skip
data = data.filter((course) => {
return !categorie.courses.includes(course);
});
categorie.courses = categorie.courses.concat(data);
categorie.save();
return res.redirect('/dash');
}).catch((err) => {
console.log(err);
res.status(400).json(err);
});
}
});
});

An alternative would involve a first query returning the courses using $in operator with Course.find() and then update the courses array in the Categorie model with Categorie.findByIdAndUpdate():
router.post('/categories/:cat_id/', function (req, res) {
Course.find({ '_id': { '$in': req.body.courses }}).exec((err, courses) => {
Categorie.findByIdAndUpdate(
req.params.cat_id,
{ '$addToSet': { 'courses': courses } },
{ 'new': true },
(err, categorie) => {
if (err){
console.log(err);
} else {
return res.redirect('/dash');
}
}
});
});
});

Mongo find() produces {} along with expected results

Hello I am trying to filter out for only video_trim in my query but the code still produces empty objects in the place of filtered out content
here is the code
const findTrims = (db, cb) => {
// Get the documents collection
const collection = db.collection(documentName);
// Find some documents
collection.find({}, {projection:{ _id: 0, name: 0, label: 0 }}).toArray((err, docs) => {
// An error occurred we need to return that to the given
// callback function
if (err) {
return cb(err);
}
assert.equal(err, null);
console.log("Found the following records");
console.log(docs)
return cb(null, docs);
});
}
module.exports = {
findTrims: cb => {
MongoClient.connect(url, (err, client) => {
if (err) {
return cb(err)
}
console.log('Connected successfully to server')
const db = client.db(dbName)
findTrims(db, (err, docs) => {
if (err) {
return cb(err)
}
// return your documents back to the given callback
return cb(null, docs)
})
})
}
}
the output of the find is this
[ {}, {}, {}, {}, { Video_trim: ' ' } ]
How do I get rid of the {}?

Pass some conditions to filter. f.e. collection.find({"Video_trim": { $exists: true }}, { _id: 0, name: 0, label: 0 })

Getting records from DynamoDB recursively using Q.Promises

I am having trouble implementing Q promises with recursive dynamodb call, new to nodejs and q, considering the limitations of the dynamodb to retrieve results, we need to run recursive query to get the required results.
normally we use the query with Q implementation something like this as
function getDBResults(){
var q = Q.defer();
var params = {
TableName: mytable,
IndexName: 'mytable-index',
KeyConditionExpression: 'id = :id',
FilterExpression: 'deliveryTime between :startTime and :endTime',
ExpressionAttributeValues: {
':startTime': {
N: startTime.toString()
},
":endTime": {
N: endTime.toString()
},
":id": {
S: id.toString()
}
},
Select: 'ALL_ATTRIBUTES',
ScanIndexForward: false,
};
dynamodb.query(params, function(err, data) {
if (err) {
console.log('Dynamo fail ' + err);
q.reject(err);
} else {
console.log('DATA'+ data);
var results = data.Items;
q.resolve(results);
}
});
return q.promise;
}
getDBResults.then(
function(data) {
// handle data
},
function(err) {
//handle error
}
);
Using recursive query I can get the results but I need those results to be used in another function, but because of nodejs async nature,the next function calls happens already before the recursive query function finishes its job, now I want that I get all the results from the recursive query function and then get as a promise to a new function and finally handle all the data.
recursive query for dynamodb looks like this.
function getDBResults(){
//var q = Q.defer();
params = {
TableName: mytable,
IndexName: 'mytable-index',
KeyConditionExpression: 'id = :id',
FilterExpression: 'deliveryTime between :startTime and :endTime',
ExpressionAttributeValues: {
':startTime': {
N: startTime.toString()
},
":endTime": {
N: endTime.toString()
},
":id": {
S: id.toString()
}
},
Select: 'ALL_ATTRIBUTES',
ScanIndexForward: false,
};
dynamodb.query(params, onQueryCallBack);
}
function onQueryCallBack(err, data) {
if (err) {
console.log('Dynamo fail ' + err);
console.error("Could not query db" + err);
} else {
if (typeof data.LastEvaluatedKey != "undefined") {
console.log("query for more...");
params.ExclusiveStartKey = data.LastEvaluatedKey;
dynamodb.query(params, onQueryCallBack);
}
data.Items.forEach(function(item) {
allResults.push(item);
});
//console.log('NO:OF Results:' + allResults.length);
//q.resolve(tickets);
//});
}
Now I want that I can get the results as promise finally so I can handle them in the next function like this.
getDBResults.then(
function(data) {
// handle data
},
function(err) {
//handle error
}
);
Please help me on this, sorry if its a stupid question but recursive calls with promises have made a hurdle for me.
Thanks

First of all, keep the promisified function you already have. Use it as a building block for the recursive solution, instead of trying to alter it!
It might need two small adjustments though:
function getDBResults(startKey){
// ^^^^^^^^
var q = Q.defer();
var params = {
ExclusiveStartKey: startKey,
// ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
… // rest as before
};
dynamodb.query(params, function(err, data) {
if (err) {
q.reject(err);
} else {
q.resolve(data);
// ^^^^ Not `data.Items`
}
});
return q.promise;
}
Now we can use that to trivially implement the recursive solution:
function getRecursiveDBResults(key) {
return getDBResults(key).then(function(data) {
if (typeof data.LastEvaluatedKey != "undefined") {
return getRecursiveDBResults(data.LastEvaluatedKey).then(items) {
return data.Items.concat(items);
});
} else {
return data.Items
}
});
}

Here is how i solve the problem, Thanks Bergi for your solution as well
function getDBResults() {
var q = Q.defer();
var dynamodb = core.getDynamoDB();
params = {
TableName: mytable,
IndexName: 'mytable-index',
KeyConditionExpression: 'id = :id',
FilterExpression: 'deliveryTime between :startTime and :endTime',
ExpressionAttributeValues: {
':startTime': {
N: startTime.toString()
},
":endTime": {
N: endTime.toString()
},
":id": {
S: id.toString()
}
},
Select: 'ALL_ATTRIBUTES',
ScanIndexForward: false,
};
var results = [];
var callback = function(err, data) {
if (err) {
console.log('Dynamo fail ' + err);
q.reject(err);
} else if (data.LastEvaluatedKey) {
params.ExclusiveStartKey = data.LastEvaluatedKey;
dynamodb.query(params, callback);
} else {
q.resolve(results);
}
data.Items.forEach(function(item) {
results.push(item);
});
}
dynamodb.query(params, callback);
return q.promise;
}