MongoDB

Database:-

MongoDB stores data in the form JSON objects, unlike relational databases that store data in the form of Tables.

Collection

Like tables in Relational databases, collections are collections JSON documents/objects in MongoDB.

Document

Like rows in Relational databases, document is a row of JSON object.

Mongoose

There are two clients for using MongoDB in NodeJs, they are Mongoose and MongoClient. MongoClient is a complex version of the MongoDB with core properties included. Mongoose is a simple client for getting started and creating mongo collections in NodeJs.

const mongoose = require('mongoose');

mongoose.connect('mongodb://localhost/playground')
.then(()=>{
    mongoLog("Connected to MongoDB");
})
.catch(error => {
    console.log("Couldn't connect to MongoDB: ",error.message)
});

Schema Object

As MongoDB stores information in the form of JSON objects, we need to store the data as key-value pairs, and maintain a schema for creating the collection object.

const courseSchema = new mongoose.Schema({
    name: String,
    author: String,
    tags: [String],
    date: {type: Date, default: Date.now},
    isPublished: Boolean
});

Create a Document

Paging Logic

const pagesize = k;
const pageNumber = l;

const courses = Course
    .find({ author: Mosh, isPublished: true})
    .skip((PageNumber-1)*pagesize)
    .limit(pagesize)
    .select({name: 1, author: 1, tags: 1});

Custom Validation

// custom validator
    validate: {
       validator: function (v){
            return  v && v.length>0;
     },
     message: 'A course should have atleast one tag'
}

Async Validation

// Async Validation
validate:{
    isAsync: true,
    validator: function (v, callback){
        setTimeout(()=>{
            const result = v && v.length>0;
            callback(result)
        }, 4000);
    },
    message: 'A course should have atleast one tag'
}

bprakashputta/mongo