Develop Reference

Is there any way that I don't use duplicate(or copy) variables for redisJSON?

Basically, I am trying to store a JSON of my application in redis using redisJSON. And I have different functions here and there in the project where I modify and update the json. Now currently, when I tried storing and updating the values in redis, I have to continuously duplicate the values to make changes and then update it back to redis. Is there any alternative for this procedure?
const addUser = async () => {
try {
const USERS_KEY = 'users';
let mainUsers;
mainUsers = await redisClient.json.get(USERS_KEY, {
path: '.',
});
if (!mainUsers) {
await redisClient.json.set(USERS_KEY, '.', {});
mainUsers = await redisClient.json.get(USERS_KEY, {
path: '.',
});
}
const mainUsersCopy = { ...mainUsers };
console.log('The actual object we need', mainUsersCopy);
const newUser = {
socketId: 123,
roomId: 456,
teamName: teamA,
rank: 69,
userName: 'X'
};
mainUsersCopy[userName] = newUser;
await redisClient.json.set(USERS_KEY, '.', mainUsersCopy);
return { status: 2, userObj: mainUsersCopy[userName] };
} catch (err) {
console.log(err);
}
};
I have given an example of above and based on that can you guys provide me a solution for not using mainUsersCopy. FYI, console logging the mainUsers we get:
mainUsers is here [object Object]
So that is why the mainUsers has been destructured. Thanks in advance.

You shouldn't need to copy anything here. Just set the value within the JSON document that you want to set using .set:
const newUser = {
socketId: 123,
roomId: 456,
teamName: teamA,
rank: 69, /* nice */
userName: 'X'
};
await redisClient.json.set(USERS_KEY, `.${newUser.userName}`, newUser);
This should set the object newUser within the existing the JSON document, creating a new key in it called, in this example X.

Mongoose populate returns empty array or list of ObjectIds

I am practicing my express.js skills by building a relational API and am struggling to populate keys in a schema.
I am building it so I have a list of properties, and those properties have units. The units have a propertyId key.
This is currently returning an empty array, whereas if i remove the populate({}) it returns an array of ObjectIds.
I've read a number of posts and some people solved this by using .populate({path: 'path', model: Model}); but this doesn't seem to be doing the trick. I think it might be the way I am adding a propertyId to the unit but I'm not sure. Can anyone see where I am going wrong? Any help will be massively appreciated.
Here are the schemas.
Property:
const mongoose = require('mongoose');
const { Schema } = mongoose;
const PropertySchema = new Schema({
title: {
type: String,
required: true
},
date: {
type: Date,
default: Date.now
},
units: [
{
type: mongoose.Schema.Types.ObjectId,
ref: 'unit'
}
]
});
module.exports = Property = mongoose.model('property', PropertySchema);
Unit:
const mongoose = require('mongoose');
const { Schema } = mongoose;
const UnitSchema = new Schema({
title: {
type: String,
required: true
},
propertyId: {
type: Schema.Types.ObjectId,
ref: 'property'
}
});
module.exports = Unit = mongoose.model('unit', UnitSchema);
I am then creating the unit like this:
-- api/properties/:id/units --
router.post('/:id/units', async (req, res) => {
// Get fields from req.body
const { title } = req.body;
// Get current property
const property = await Property.findById(req.params.id);
try {
// Throw error if no property
if (!property) {
return res.status(400).json({ msg: 'Property not found' });
}
// Create new unit
const newUnit = new Unit({
title,
propertyId: req.params.id
});
// Add new unit to property's units array
property.units.unshift(newUnit);
// Save property
await property.save();
// Return successful response
return res.status(200).json(property);
} catch (error) {
console.error(error.message);
return res.status(500).send('Server error');
}
});
And trying to populate in the GET request
-- /api/properties/:id/units --
const Unit = require('../../models/Unit');
router.get('/:id/units', async (req, res) => {
const property = await Property.findOne({ _id: req.params.id }).populate({path: 'units', model: Unit});
const propertyUnits = property.units;
return res.status(200).json(propertyUnits);
});
If i remove the .populate({path: 'units', model: Unit});, I get a list of unit id's like this:
[
"5ff7256cda2f5bfc1d2b9108",
"5ff72507acf9b6fb89f0fa4e",
"5ff724e41393c7fb5a667dc8",
"5ff721f35c73daf6d0cb5eff",
"5ff721eb5c73daf6d0cb5efe",
"5ff7215332d302f5ffa67413"
]

I don't know, why you don't try it like this:
await Property.findOne({ _id: req.params.id }).populate('units')
I've been try that code above and it's working.
Note: Make sure to check your req.params.id is not null or undefined and make sure the data you find is not empty in your mongodb.
Updated: I've been try your code and it's working fine.

The issue was caused by inconsistent naming and not saving the new created unit as well as the updated property.
I double checked all my schema exports and references and noticed I was using UpperCase in some instances and LowerCase in others, and saved the newUnit as well as the updated property in the POST request and it worked.

push array in const inside .then

I'm trying to push a value inside a const but its in a .then and it's not working do you know how can I do that ?
I get a value in my console.log(newResult) in my if but the data is not pushed in my const newResult in the return
res.status(200).json(newResult);
.then(function (friends) {
if (friends) {
const newResult = [];
friends.forEach((r) => {
if (r.UserID == userFound.id) {
models.User.findOne({
where: {
id: r.idFriend
}
})
.then(function(userFound) {
newResult.push({
id: r.id,
user: {
id: r.User.id,
email: userFound.email,
username: userFound.username
}
});
console.log(newResult)
})
} else
newResult.push({
id: r.id,
user: {
id: r.User.id,
email: r.User.email,
username: r.User.username
}
});
console.log(newResult)
});
res.status(200).json(newResult);
}
}
every test realised return an empty tab when i go in my if condition

It will never work because, you are doing async calls
models.User.findOne inside forEach.
You'll get results on console.log when async call to database for fetching user is complete.
But before this all happens the forEach is done executing and code hits the line res.status(200).json(newResult); and you see no results from your if condition.
Instead of using this approach go for mongoose populate and populate userObject based userID while finding friends this way you won't have to do async call inside the forEach.
Read about mongoose populate at: http://mongoosejs.com/docs/populate.html

Using Model.create() and save() inside for loop

Hey so I'm pretty new to Javascript and Node but I'm running into an issue that's been bothering me for a while.
I have a User model and an Image model, I'm using Multer to upload an array of images and trying to loop through this array, create a new Image model for each, then unshift that Image into my User's photos. I have Multer set up to successfully fills req.files. Here's the code.
router.post("/users/:user/photos/upload", middle.isLoggedIn, upload.array("photos", 4), function(req, res) {
User.findById(req.params.user, function(err, foundUser) {
for(var i = 0, len = req.files.length; i < len; i++) {
Image.create(req.files[i], function(err, newImage) {
if(err) {
return console.log(err.message);
}
newImage.human = foundUser;
newImage.save();
console.log(newImage);
foundUser.photos.unshift(newImage);
foundUser.save();
});
}
console.log(foundUser);
});
});
console.log(foundUser); seems to execute and print before console.log(newImage);
User Model
var mongoose = require("mongoose"),
passportLocalMongoose = require("passport-local-mongoose");
var UserSchema = new mongoose.Schema({
username: String,
password: String,
firstName: String,
lastName: String,
city: String,
photos: [
{
type: mongoose.Schema.Types.ObjectId,
ref: "Image"
}
]
});
HumanSchema.plugin(passportLocalMongoose);
module.exports = mongoose.model("User", UserSchema);
Image Model
var mongoose = require("mongoose");
var ImageSchema = new mongoose.Schema({
fieldname: String,
originalname: String,
mimetype: String,
filename: String,
destination: String,
size: Number,
path: String,
human: {
id: {
type: mongoose.Schema.Types.ObjectId,
ref: "Human"
}
}
});
module.exports = mongoose.model("Image", ImageSchema);
This is my first stackoverflow question so let me know if I didn't post enough code.
I think it have something to do with Image.create() being asynchronous, and I'm still trying to learn more about this and promises, but I still don't fully understand how it's relevant in my code.

Use Mongoose's promise support.
Promise.all allows you to resolve an array of promises.
async/await control flow for Promises.
I'm not sure your code as it is structured will work without a serial loop due the async code that can execute in any order. I'm not sure that triggering multiple foundUser.save()s on the same object at different times will work out very well. Holding database objects in memory for a long time can open up more concurrency data issues too.
The Bluebird promise library includes some additional helpers like Promise.each which will serially complete promises before the next starts which may be of use here.
const Promise = require('bluebird')
router.post("/users/:user/photos/upload", middle.isLoggedIn, upload.array("photos", 4), async function(req, res, next) {
try {
let foundUser = await User.findById(req.params.user)
await Promise.each(req.files, async file => {
let newImage = await Image.create(file)
newImage.human = foundUser;
await newImage.save()
console.log(newImage)
foundUser.photos.unshift(newImage)
await foundUser.save()
}
console.log(foundUser)
}
catch (err) {
next(err)
}
})
Other methods like .map and .reduce help make standard array/loop type operations with Promises easier to do.
Atomic Updates
In regards to the concurrency issue, any updates you can do in MongoDB that are "atomic" are a good thing. So instead of selecting something, modifying it in JS, then saving it back, you send the update to Mongo and let the db server deal with it. No matter what order you send the updates to the database, they will always be updating the latest copy of data.
In this case the array unshift can be completed without the initial select by using findByIdAndUpdate and $push (it can be made to push at position 0, there is no $unshift in mongo).
If you add a method to your User model for the adding the photo:
addPhoto(user_id, newImage){
return User.findByIdAndUpdate(
user_id,
{ $push: { photos: { $each: [newImage], $position: 0 } } } }
{ safe: true, new: true }
)
}
So the code would look like
const Promise = require('bluebird')
router.post("/users/:user/photos/upload", middle.isLoggedIn, upload.array("photos", 4), async function(req, res, next) {
try {
let foundUser = await User.findById(req.params.user)
if (!foundUser) throw new Error(`No user found: $user`)
let results = await Promise.map(req.files, async file => {
let newImage = await Image.create(file)
newImage.human = foundUser
await newImage.save()
console.log(newImage)
let user_update = await User.addPhoto(req.params.user, newImage)
console.log(user_update)
}
}
catch (err) {
next(err)
}
})

How can i save results from mongoose query to a variable

I'm trying to save some objects into an array by looping through a list of songs in an album, looking for relevant songs and trying to save into array for later use. is there any way to achieve this?
I need some explanation using mongoose.
exports.playlistPlayer = function (req, res, next) {
Playlist.findById({
_id: req.body.playlist._id
}, (err, playlist) => {
var customAlbum = []; //This variable it's inside the same block i believe
playlist.songs.forEach(function (song) {
Song.findById({
_id: song.song_id
}, (err, songs) => {
var customSong = {
title: songs.title,
time: songs.time,
source: songs.source,
song_id: songs._id
}
customAlbum.push(customSong)
console.log(customAlbum) //it works here
});
});
console.log(customAlbum) //it returns an empty array here where i need the data
});
};

The problem is that the findById method is also asynchronous. I recommend you to learn about promises in javascript. One possible solution would be using the async/await feature from ES7:
// asynchronous function
exports.playlistPlayer = async (req, res, next) => {
// wait for the findById method promise to resolve
const playlist = await Playlist.findById({
_id: req.body.playlist._id
})
// wait for finding all songs in db whose id's are in
// the playlist.songs array
const songs = await Song.find({
_id: { $in: playlist.songs }
})
// create the customAlbum by using the map method to
// tramsform the song objects to the required form
const customAlbum = songs.map(song => ({
title: song.title,
time: song.time,
source: song.source,
song_id: song._id
}))
// and there you should now have your customAlbum array
console.log(customAlbum)
// now you can use it for example
// to return a response to the client:
// res.json(customAlbum)
}