How to use mongoose findById() and populate() in javascript? - arrays

Question

Im trying to create a list of items for each users, which means user can create items and ı want to keep that data for each user.
Which I create two different schemas for that in:
user.js
var mongoose = require('mongoose');
var Schema = mongoose.Schema;
userSchema = new Schema({
unique_id: Number,
email: String,
username: String,
password: String,
passwordConf: String,
teamname: String,
items: [{ type: Schema.Types.ObjectId, ref: 'Item' }],
});
(ItemSchema = new Schema({
createrId: { type: Schema.Types.ObjectId, ref: 'User' },
productname: String,
description: String,
price: String,
totalStock: String,
})),
(Item = mongoose.model('Item', ItemSchema));
User = mongoose.model('User', userSchema);
module.exports = { Item, User };
After creating 2 schemas ı used them in index.js that routers everything together.
index.js
router.get('/create_item', function (req, res, next) {
return res.render('items.ejs');
});
router.post(
'/create_item',
function (
req,
res,
next // Try to create items in database
) {
console.log(req.body);
var itemInfo = req.body;
if (
!itemInfo.itemname ||
!itemInfo.itemdsc ||
!itemInfo.itemstock ||
!itemInfo.itemprice
) {
res.send();
} else {
var NewItem = new Item({
createrId: loggedInUser._id,
productname: itemInfo.itemname,
description: itemInfo.itemdsc,
price: itemInfo.itemprice,
totalStock: itemInfo.itemstock,
});
NewItem.save(function (err, Item) {
if (err) console.log(err);
else console.log('Item added succesfully !');
});
}
User.findById(loggedInUser._id)
.populate('items')
.exec(function (err, result) {
if (err) {
console.log(err);
} else {
console.log('Suceess ? : ', result.items);
console.log(loggedInUser._id);
}
});
}
);
I keep the data for loggedInUser in '/login' so it is return me a value.
My output is
"Suceess ? :[]
6379921faf39150008fa1b88
Item added succesfully !
Which ı think the problem is from the output it trying to populate item after Item is created but how can ı solve this problem ?
Thanks

Answer 1

The problem is that your code is not executing sequentially (NewItem.save logs after User.findById).
Try to use async await, also you will need to add the newly created item _id to the corresponding User to add the new reference to the items array:
router.post(
'/create_item',
async function (
req,
res,
next // Try to create items in database
) {
console.log(req.body);
try {
var itemInfo = req.body;
if (
!itemInfo.itemname ||
!itemInfo.itemdsc ||
!itemInfo.itemstock ||
!itemInfo.itemprice
) {
return res.send('Incomplete parameters');
}
const newItem = await Item.create({
createrId: loggedInUser._id,
productname: itemInfo.itemname,
description: itemInfo.itemdsc,
price: itemInfo.itemprice,
totalStock: itemInfo.itemstock,
});
const result = await User.findByIdAndUpdate(loggedInUser._id, {
$push: { items: newItem._id },
}, { new: true })
.populate('items')
.exec();
console.log('Suceess ? : ', result.items);
console.log(loggedInUser._id);
return res.send('Finished');
} catch (e) {
console.log(e);
}
}
);