Mongoose pagination from server side - node.js

Question

I am trying to add server side pagination to a NodeJS, Express and MongoDB API. The API use mongoose to handle the database. I am lost in how to customize the response from the Controller.
Model:
const mongoose = require('mongoose');
const Schema = mongoose.Schema;
const clientSchema = Schema({
code: {
type: String,
required: [true,'Code no puede estar vacio']
},
name: {
type: String,
required: [true,'Name no puede estar vacio']
}
},{
timestamps: true
});
const Client = module.exports = mongoose.model('clients',clientSchema);
Controller for get all clients:
const mongoose = require("mongoose");
const Client = require('../models/client');
const clientController = {};
clientController.index = (limit, callback) => {
Client.find(callback).limit(limit);
};
module.exports = clientController;
Route to get the clients:
app.get('/api/clients', (req, res) => {
Client.index(limit,(err, client) => {
if (err) {
res.status(500).json({
msg: "Error en aplicacion",
err
});
}
res.status(200).json(client);
});
});
How can I customize the result in the controller to something like this:
[
{
"totalRecords":"99999999999",
"offset":"888888",
"page":"4",
"nextPage":"5"
"result":{...}
}
]
I already have a function to calculate the pagination, But I don't know how to add the information about the pagination in the result of the controller.
Before I was adding the pagination data in the route, But I want to handle the pagination logic in the controller.
Or is better handle the pagination in the route?
Thanks in advance

Answer 1

You can create a method in mongoose model called as paginate :
Add this before declaring mongoose model :
clientSchema.methods.paginate = function(pageNo, callback){
var limit = 10;
var skip = pageNo * (limit - 1);
var totalCount;
//count documents
this.count({}, function(err, count)){
if(err){
totalCount = 0;
}
else{
totalCount = count;
}
}
if(totalCount == 0){
return callback('No Document in Database..', null);
}
//get paginated documents
this.find().skip(skip).limit(limit).exec(function(err, docs){
if(err){
return callback('Error Occured', null);
}
else if(!docs){
return callback('Docs Not Found', null);
}
else{
var result = {
"totalRecords" : totalCount,
"page": pageNo,
"nextPage": pageNo + 1,
"result": docs
};
return callback(null, result);
}
});
});
const Client = module.exports = mongoose.model('clients',clientSchema);
Then in controller change :
app.get('/api/clients', (req, res) => {
//You could put page number in request query ro request params
Client.paginate(req.body.pageNo, function(err, response) {
if (err) {
return res.status(500).json({
message : "Error en aplicacion",
error : err
});
}
return res.status(200).json(response);
});
});