Architecture in Node JS wirh Controller, Service and Repository - node.js

Question

In order to keep clean architecture of my node.js I have controllers, services and repositories.
Data flow: controller -> service -> repository -> service -> controller.
In this flow (in simple user story) repository returns data to service and service to controller. But repository should process requests to external storage.
Right now I have the callback difficulty, how can I implement a nested callback between controller and repository?
My Controller:
exports.clientes_get = async function (req, res) {
Cliente.find(function(err,params) {
if (err)
res.send(err);
res.json(params);
});
}
My Service:
ClienteGet(req) {
var response;
repo.get(req.params.clienteId, (err, res) => {
response = res;
//console.log(response); -> have data
});
//console.log(response); -> doesnt have data
return response;
};
My Repository:
get(clienteId, data) {
mongoose.model('Cliente').findById(clienteId, data);
};
How can i do this?

Answer 1

Using Callbacks
If you insist on using callbacks:
Controller:
// notice that the `async` here was not necessary
exports.clientes_get = function (req, res) {
// the `function(err, params) {...}` here is your callback
ClienteGet(req, function(err, params) {
if (err) {
return res.send(err);
}
res.json(params);
});
}
Service:
ClienteGet(req, callback) {
// simply pass the callback argument directly to the `repo.get` call
repo.get(req.params.clienteId, callback);
};
Repository:
get(clienteId, callback) {
// again, just pass the callback here
mongoose.model('Cliente').findById(clienteId, callback);
};
Using Promises
I personally recommend wrapping you code in
Promises,
because they are more flexible than callbacks, and modern JavaScript uses
Promises heavily. It's pretty much the new standard... In fact, the async /
await syntax is leveraging Promises under the hood.
Here's a rough sketch of how you could use Promises:
Controller:
exports.clientes_get = function (req, res) {
return ClienteGet(req)
.then((data) => {
res.json(data);
})
.catch((err) => {
res.send(err);
});
}
Service:
ClienteGet(req) {
return new Promise((resolve, reject) => {
repo.get(req.params.clienteId, (err, res) => {
if (err) {
return reject(err);
}
resolve(res);
//console.log(response); -> have data
});
});
};
Repository:
get(clienteId) {
return new Promise((resolve, reject) => {
mongoose.model('Cliente').findById(clienteId, function(err, document) {
if (err) {
return reject(err);
}
resolve(document);
});
});
};