Backend Topics

1 . CRUD Operations : CRUD operations is backend database management system

which helps to create ,read , update and delete documents .
Create Operations: It is a creating or inserting method . It means when collection doesn’t

exists this insert operations will add or create new documents to the collection . In MongoDB

creating operations may follow this way :
db.collection.insertOne () [ It is use for inserting one new document to collections ]
db.collection.insertMany () [ It is use for inserting many new documents to collections ]
One inserting document code is here to see :
db.products.insertOne (
{
name : “ Bag ”,
price : “ 22 “ ,
rating : “ 4 ”
}
)

Read Operations: It is a query method of document collection . It finds out our searching

collections from mongoDB may or from other databases . We can search data from one or

more data from the database by using these read operations . That means it can easily

specify criteria and filter them then return these documents .
db.collection.findOne ( query things are here ) [ It is use for finding one document from collections ]
db.collection.find ([ ]) [ It is use for finding many documents from collections ]
One example is here :
db. products. find (
{ price : { $ price : 15} },
{ name : 2 }
) .limit ( 6 )

Read operations follow different query methods for searching our needs . Like
Can query one document from a database based on specific identification .
It also finds an array and returns lots of documents .
Query on Embedded or Nested documents.
Query an Array of Embedded documents.

Update Operations: Update is a operation of modify existing data documents in database
collection . It mostly like read operation because it also follow the query or specify
criteria for updating data .
For an example :
db.collection.updateOne ( query things are here ) [ It is use for updating one document from collections ]
db.collection.updateMany ([ ]) [ It is use for finding many documents from collections ]
Example :
db.products.updateMany(
{ price : { $ price :23 }} ;
{ $ set : { name : “ shoes ”}}
)

Delete Operations: It is a deleting operation it means it remove document from database
permanently . It also use the criteria of specify and filtering method for exact identifying the
document in collection . Delete operation remove data in this way :
db.collection.DeleteOne ( query things are here ) [ It is use for deleting one document from collections ]
db.collection.deleteMany ([ ]) [ It is use for deleting many documents from collections ]
db .products.deleteMany (
{ name : “ shoes”} ,
)

2. JWT : It’s full form is JSON Web Tokens . It is an internet process for securing data or information between two parties. It holds encoded JSON objects and signs using cryptographic algorithms . It helps to validate the sender’s identification and is made up of three parts which are separated by dots ( . ) and also using base64 . In decoding we will get two JSON string :
Header and payload . [ Headers contain the type of token like JWT in the case and singing algritom and payload contains the claim ]
Signature . [ It ensures that the token hasn;t been altered ]

3.Mongoose: Mongoose is an object Data Modeling library for MomgoDB and Node.js.It manages Data ,previous schema validation,and is used to translate between objects in code and the representation of those objects in MongoDB.MongoDb is schema -less Nosql document database.It means one can store JSON documents in it.The main reason of using Nosql is that it speeds up application development and reduces the complexity of developments.

Ex- {
”Id”:1,
“email”:”[e-mail]”,
“phone”:2125444447
}
{
”Id”:2,
“email”:”[e-mail]”,
“phone”:21277444
}
{
”Id”:3,
“email”:”[e-mail]”,
“Phone”:245557
}

Benefits of using Mongoose: They are-
Schemas: Mongoose defines a schema for data models so the documents follow a specific structure with predefined data types.

Validation: Mongoose has built-in validation for schema definitions.It saves us from writing a bunch of validation code that we have to write with the MongoDB driver.

Instance Method: It provides optional pre and post save operations for data models.It is easy to define hooks and custom functionality on reads and writes.It also organizes methods within schema definition.

Returning result: Mongoose makes it easier to return updated documents or query results.

4.Express js: Express is a minimal and flexible Node js web application framework that provides a set of features to develop web and mobile applications.It designed for building single-page,multi-page and hybrid web applications.It is the back end component of MERN stack which includes MongoDB for database and Node js for Javascript runtime environment.It makes it easier to organize our application’s functionality with middleware and routing.It also adds helpful utilities to Node js’s HTTP objects.It facilities the rendering of dynamic HTTP objects.It is an open source software distributed under the MIT license, which generally means that it’s free to develop and use.