Node.js Sequalize creating new rows in forEach loop - node.js

Question

I'm trying to create new rows in the database using Sequalize ORM. I receive an array of collections from req.query.collections. For each of those collections I need to create a new userCollection. If none userCollections were created, I wanna respond with internal server error (line 41), otherwise return an array of objects with newly created userCollections.
The problem is, I keep getting an internal server error when I make test requests from Postman. When I check my database, I see that those userCollections were created, so no error occurred.
I know why this happens: because userCollection.build({ stuff }).save() returns a promise. So when I try to console.log userCollections from within .then() statement, I get an array with a newly created collections, just like I should. But by that time server has already responded with internal server error.
Here's my function code:
exports.addCollections = async (req, res, next) => {
const libraryId = req.params.libraryId;
const collections = req.query.collections;
if (!collections)
next(Boom.forbidden());
const userCollections = [];
collections.forEach(async (collectionId, index) => {
const collection = await Collection.findByPk(collectionId);
if (!collection)
return next(Boom.notFound());
userCollection.build({
user_id: req.user.id,
library_id: libraryId,
public_collection_id: collection.id,
title: collection.title,
description: collection.description
})
.save()
.then(newUserCollection => {
userCollections.push(newUserCollection.get({ plain: true }));
// should be printed first, but comes second
// prints out the array with newly created record
console.log(userCollections);
})
.catch(error => {
console.log(error);
});
});
// should be printed second, but comes first
// prints out empty array
console.log(userCollections);
if (userCollections.length === 0) {
next(Boom.internal());
}
res.json(userCollections);
}

Answer 1

Posting the solution
Thanks to Sebastien Chopin who created this tutorial:
https://codeburst.io/javascript-async-await-with-foreach-b6ba62bbf404
So I added this function:
const asyncForEach = async (array, callback) => {
for (let index = 0; index < array.length; index++) {
await callback(array[index], index, array)
}
}
And instead of collections.forEach...(blah blah) (line 10 of the code posted in the question) I do:
try {
await asyncForEach(collections, async (collectionId, index) => {
const collection = await Collection.findByPk(collectionId);
if (!collection)
return next(Boom.notFound());
userCollection.build({
user_id: req.user.id,
library_id: libraryId,
public_collection_id: collection.id,
title: collection.title,
description: collection.description
})
.save()
.then(newUserCollection => {
userCollections.push(newUserCollection.get({ plain: true }));
console.log(userCollections);
})
.catch(error => {
console.log(error);
});
})
} catch (err) {
return next(Boom.internal(err.message));
}