OOP with MVC using Mongoose & Express.js

I am creating an Express.js application where I want to use the MVC and Mongoose pattern to map documents in a MongoDB database. I created a folder for models and I want to get everything from abstract classes (Javascript) to better organize my code.

I am confused that the best way is to organize abstract classes and set the default values ​​that should be in every instance of the models. For example, one way is to use Mongoose schemas for abstract classes and then use Mongoose models for the models themselves:

Feline.js:

var mongoose = require('mongoose');

var Feline = mongoose.Schema({
  size: 'Number'
});

Feline.methods.getSize = function () {
  return this.size;
}

module.exports = Feline;

      

        
        
        
      

    

HouseCat.js:

var mongoose = require('mongoose')
, FelineSchema = require('./Feline.js');

var HouseCatModel = mongoose.model('HouseCat', FelineSchema)
, HouseCat = new HouseCatModel({
  size: 1 //Domesticated cats are small
});

module.exports = HouseCat;

      

        
        
        
      

    

There are several problems with this design. First, I think there must be a better way to set specific properties for each model without instantiating a new model object every time the client wants to create a new instance of the model type. For another, using this schema Mongoose is required in every model file and the code is customized specifically to use mongoose, which means it will be difficult to switch to a different ODM if we want to do so in the future.

Is there a better way to code this? And is there a design pattern that is easy enough to implement in Node that makes it easy to change the ODM?