joselegit joselegit - 5 months ago 33
Node.js Question

mongoose pagination from server side

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 Source

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) => {
  Client.paginate(pageNo, function(err, response){

    if (err) {
      return res.status(500).json({
        message : "Error en aplicacion",
        error : err
      });
    }
    return res.status(200).json(response);
  });

});