Search and lookup arrays nested in multiple objects - node.js

Question

I find all websites that match the IDs I have in my array and in the below case it is two websites. I then want to look inside each of the conversations arrays of those websites and search a different collection called conversations for conversations that match those IDs. I then want to grab some/all of the fields from those conversations and add it to the JSON document I already have, grouping them by conversation within each website. I've been playing around with aggregate, unwind, and group but can't seem to get anything to work.
router.post('/staffLoadUpTwo', async (req, res) => {
var userId = '5e8f964a9c2d0780c0163825';
const company = await Company.findOne({ 'roles.admins': userId });
var unwrappedCompany = JSON.parse(JSON.stringify(company));
console.log(unwrappedCompany.websites);
const website = await Website.find({
_id: { $in: unwrappedCompany.websites },
});
// const unwindTest = await Website.aggregate([{$unwind : "$conversations"}]);
console.log(website);
});
console.log(website);
[ { conversations: [ '5e90d9ceb089812c9ba1a67b', '5e8f5a6a2582bf629998c3fd' ],
_id: 5e949cc02483c0c0056a1a98,
domain: 'http://x.com',
__v: 0 },
{ conversations: [ '5e8e23595ce6d611cec5033f', '5e8e3afee8e95e1ff94650d3' ],
_id: 5e949ce8f53450c0341b36cd,
domain: 'http://y.com',
__v: 0 } ]
ideal output
[{
_id: "5e949cc02483c0c0056a1a98",
domain: 'http://x.com'
conversations: [
{conversationId: "5e90d9ceb089812c9ba1a67b", messages: {messageArray: ['a'], timeSent: 2}},
{conversationId: "5e8f5a6a2582bf629998c3fd", messages: {messageArray: ['b'], timeSent: 6}}
]
}
_id: "5e949ce8f53450c0341b36cd",
domain: 'http://y.com'
conversations: [
{conversationId: "5e8e23595ce6d611cec5033f", messages: {messageArray: ['c'], timeSent: 1}},
{conversationId: "5e8e3afee8e95e1ff94650d3", messages: {messageArray: ['d'], timeSent: 8}}
]
}]

Answer 1

You need not stress yourself with MongoDB aggregation. Since you're using Mongoose, you can easily use mongoose populate to achieve the result you described in the question.
Provided you've defined the website scheme to be something like this:
const websiteSchema = {
// ...schema definition for other properties
/* Note the ref property used below, the value must be the name of the
conversation model, i.e the stringValue you passed into
mongoose.model(<stringValue>, conversationSchema); */
conversations: [ { type: mongoose.Types.ObjectId, ref: 'Conversations' } ]
}
A mongoose query like this:
const website = await Website.find({
_id: { $in: unwrappedCompany.websites },
}).populate('conversations');
will output an array of website documents whose conversations field are populated i.e, you get the actual conversation document and not just their _ids.
More about Mongoose populate here