sailsjs use mongodb without ORM - node.js

Question

I want to use mongodb with sails but without any ORM. So below is my service to connect mongodb.
Service:
//DbService.js
const MongoClient = require('mongodb').MongoClient;
module.exports = {
db:function(req, res){
var connect=MongoClient.connect("mongodb:***********").then(function (err, database) {
if(err) console.log(err);
else{
database=database.db('*****');
return connect;
}
});
}
}
After connection i have called it in controller, But getting TypeError: Cannot read property 'then' of undefined.
controller:
//HomeControlelr.js
module.exports = {
index:function(req, res){
DbService.db().then(function(err,db) {
console.log(db);
})
}
};

Answer 1

First npm i mongodb because you'll need to wrap any ID's with new ObjectID(idStr).
Then you can do this:
const collection = Pet.getDatastore().manager.collection(Pet.tableName);
const res = await collection.find({ name: { $regex: /blue/ } });
const dataWithObjectIds = await res.toArray();
const dataWithIds = JSON.parse(JSON.stringify(rawDataArr).replace(/"_id"/g, '"id"'));
I created a helper function to do all of this for us:
/**
* Use by chaining as if you were acting on a collection. So can use .find .aggregate etc.
* Returns json searializable data.
*
* #param {class} model A model
* #param {number} cnt - Number of chains on this, so I know when it reached the end
*/
function nativeMongoQuery(model, cnt) {
const collection = model.getDatastore().manager.collection(model.tableName);
let callCnt = 0;
let req;
const proxy = new Proxy({}, {
get: (_, method) => (...args) => {
if (!req) req = collection[method](...args);
else req = req[method](...args);
callCnt++;
if (callCnt === cnt) {
return (async function() {
const rawDataArr = await req.toArray();
return JSON.parse(JSON.stringify(rawDataArr).replace(/"_id"/g, '"id"'));
})();
} else {
return proxy;
}
}
});
return proxy;
}
module.exports = nativeMongoQuery;
I don't like the JSON parse and stringify and global replace. But if I don't do the stringify, then mongo _id's are all ObjectIds.
Use it like this:
const { ObjectId } = require('mongodb');
function makeObjectId(id) {
return new ObjectId(id);
}
const ownerIds = ['5349b4ddd2781d08c09890f4', '5349b4ddd2781d08c09890f5']
const ownerObjectIds = ownerIds.map(makeObjectId);
await nativeMongoQuery(Pet, 2).find({ owner: { $in: ownerObjectIds } }).sort({ dueAt: 1 });
Here is another example:
const mostRecentlyCreatedPets = await nativeMongoQuery(Pet, 1).aggregate([
{ $match: { owner: { $in: ownerObjectIds } } },
{ $sort: { createdAt: -1 } },
{ $limit: 1 }
]);
The cnt argument tells you how many things you have chained off of there.

Answer 2

As you can see in docs MongoClient.connect() doesn't return Promise object. Instead of this use callback function
module.exports = {
db:function(){
var connect = MongoClient.connect("mongodb:***********", function (err, database) {
//...
}
});
}
}
btw. Your call DbService.db function in controller will also fail, cuz your service function also doesn't return Promise
Before you go on, read something about Promises and callback functions