Fetch data from multiple collections in mongo - node.js

Question

I have some collections shown like below which is holding relationships, relation between testMaster and testDoc is holding inside the testDocMaster
For eg:
testMaster {
_id: "Schema.Objectid",
name: "String" //master name
}
testDoc {
_id : Schema.ObjectId,
name: "String", //doc name
other datas
}
testDocMaster {
masterId: "_id of the testMaster table",
docId : "_id of the above testDoc"
}
For each master entry, we are expecting many relations,
what would be the best way to fetch the data from the testDoc table, if I have the masterId.

Answer 1

I got it working using this:
// GLOBAL ARRAYS FOR STORING COLLECTION DATA
var collectionOne = [];
var collectionTwo = [];
app.get('/', function(req, res){
MongoClient.connect("mongodb://localhost:27017/michael", function(err, db) {
if(!err) {
console.log("We are connected");
}
db.collection("collectionOne", function(err, collection) {
collection.find().sort({order_num: 1}).toArray(function(err, result) {
if (err) {
throw err;
} else {
for (i=0; i<result.length; i++) {
collectionOne[i] = result[i];
}
}
});
db.collection("collectionTwo", function(err, collection) {
collection.find().sort({order_num: 1}).toArray(function(err, result) {
if (err) {
throw err;
} else {
for (i=0; i<result.length; i++) {
collectionTwo[i] = result[i];
}
}
});
});
// Thank you aesede!
res.render('index.html', {
collectionOne: collectionOne,
collectionTwo: collectionTwo
});
});
});
});
Now, for some reason when Node restarts, and I hit refresh, it doesn't render HTML into the front-end. However, any subsequent refresh renders the page correctly.

Answer 2

Assuming your testDocMaster schema uses ObjectId types that ref the other two collections you can use Mongoose's query population support to help with this:
TestDocMaster.findOne({ masterId: masterId})
.populate('docId')
.exec(function(err, testDocMaster) {
// testDocMaster.docId is populated with the full testDoc for the
// matching _id
});