Mongoose or MongoDB for Schema definition?

MongoDB doesn't support schema. It's a schemaless document based DB.

Mongoose is an ODM(Object Document Mapper) that helps to interact with MongoDB via schema, plus it also support validations & hooks.

Basically mongodb is schema less database we cant able to create schema directly in mongodb. Using mongoose we can able to create a schema. Simple CRUD operation using mongoose, for more info ref this link

package.json

{    "name": "product-api",    "main": "server.js",    "dependencies": {        "express": "~4.0.0",        "body-parser": "~1.0.1",        "cors": "2.8.1",        "mongoose": "~3.6.13"    }}

product.js

var mongoose     = require('mongoose');var Schema       = mongoose.Schema;var ProductSchema   = new Schema({    title: String,    price: Number,    instock : Boolean,    photo : String ,});module.exports = mongoose.model('Product', ProductSchema);// module.exports = mongoose.model('Product', ProductSchema,'optiponally pass schema name ');

server.js

var express = require('express');var bodyParser = require('body-parser');var cors = require('cors');var app = express();var mongoose = require('mongoose');var product = require('./product');app.use(bodyParser.urlencoded({ extended: true }));app.use(bodyParser.json());var port = process.env.PORT || 8090;var router = express.Router();mongoose.connect('mongodb://localhost:27017/products');// Middle Route router.use(function (req, res, next) {    // do logging     // do authentication     console.log('Logging of request will be done here');    next(); // make sure we go to the next routes and don't stop here});router.route('/products').post(function (req, res) {    console.log("in add");    var p = new product();    p.title = req.body.title;    p.price = req.body.price;    p.instock = req.body.instock;    p.photo = req.body.photo;    p.save(function (err) {        if (err) {            res.send(err);        }        console.log("added");        res.send({ message: 'Product Created !' })    })});router.route('/products').get(function (req, res) {    product.find(function (err, products) {        if (err) {            res.send(err);        }        res.send(products);    });});router.route('/products/:product_id').get(function (req, res) {    product.findById(req.params.product_id, function (err, prod) {        if (err)            res.send(err);        res.json(prod);    });});router.route('/products/:product_id').put(function (req, res) {    product.findById(req.params.product_id, function (err, prod) {        if (err) {            res.send(err);        }        prod.title = req.body.title;        prod.price = req.body.price;        prod.instock = req.body.instock;        prod.photo = req.body.photo;        prod.save(function (err) {            if (err)                res.send(err);            res.json({ message: 'Product updated!' });        });    });});router.route('/products/:product_id').delete(function (req, res) {    product.remove({ _id: req.param.product_id }, function (err, prod) {        if (err) {            res.send(err);        }        res.json({ message: 'Successfully deleted' });    })});app.use(cors());app.use('/api', router);app.listen(port);console.log('REST API is runnning at ' + port);

Mongoose helps to interact with MongoDB in terms of Object/Model so that programmer doesn't need to understand the remember the statements of MongoDB.

Also, Mongoose provides lot of methods of CRUD Operations to better understanding of DB Operations.

You can check examples here

https://developer.mozilla.org/en-US/docs/Learn/Server-side/Express_Nodejs/mongoosehttp://mongoosejs.com/docs/