CRUD operations

Pre-requisites

• Familiar with Node js and MongoDB and are installed in your machine.
• You can use Visual studio code to develop your projects.
• Install Postman to test your code

Terminology

Express

Express is a framework which runs on top of Node js for building web applications and it is more preferable as it simplifies server creation process

MongoDB

MongoDB is a no-sql database which is used widely now a days.

CRUD

CRUD is a acronym for Create, read, update and delete operations

How to start

1. create a folder in your repository
2. Open terminal and navigate to the folder you created.
3. execute npm init, which creates package.json file.
4. execute code package.json, to open the package.json in your visual studio code.

Dependencies

• Install below dependencies

npm i express mongodb body-parser --save

Code

Consider pets is a collection which has id, name and age information of pets in your local machine. You can perform CRUD operations on pets as below

const express = require('express');
const server = express();

var bodyParser = require('body-parser');

server.use(bodyParser.urlencoded({
    limit: "4mb",
    extended: false
}));
server.use(bodyParser.json({ limit: "4mb" }));

const MongoClient = require('mongodb').MongoClient;
const url = 'mongodb://localhost:27017';

let db = null;

MongoClient.connect(url, function(err, client) {
    console.log("Connected successfully to server");
    db = client.db('pets');
});

// read all pets
server.get('/pets', (req, res) => {
    db.collection('pets').find({}).toArray(function(err, docs) {
        res.send(docs);
    });
});

// read one pet information using id
server.get('/pets/:id', (req, res) => {
    console.log('req.params.id', req.params.id);
    db.collection('pets').findOne({_id: parseInt(req.params.id)}, function(err, doc){
        if(err){
            console.log(err);
            res.send(err);
        }
        else{
            console.log(doc);
            res.send(doc);
            
        }
    });
});

// insert a pet
server.put('/pets', (req, res) => {
    console.log('body', req.body);
    db.collection('pets').insertOne({_id: req.body.id,name:req.body.name,age:req.body.age});
    res.send("inserted successfully");
});


// update a pet
server.post('/pets/:id', (req, res) => {
    console.log('id', req.body.id);
    db.collection('pets').updateOne({_id: req.body.id},{$set:{name:req.body.name,age:req.body.age}});
    res.send('updated successfully');
});

// delete pet 
server.delete('/pets/:id', (req, res) => {
    console.log('id', req.body.id);
    db.collection('pets').deleteOne({_id: req.body.id});
    res.send('deleted successfully');
});
server.listen(5000);

How to run your code

1. switch to your terminal again or you can open terminal in your VS code itself.
2. Execute the below command

node index.js

How to Test

1. Get or Read pets information

• Open your browser and hit
  1. to retrieve all pets information

http://localhost:5000/pets 

2. to retrieve one pet information

http://localhost:5000/pets/2

2. Insert or PUT pets information

1. Open Postman
2. Select PUT as protocol and http://localhost:5000/pets as URL
3. Configure the headers to send JSON data by making key as Content-Type and value as application/json.
4. Send sample test data in body.

Sample test data:

{
	"id": 3,
	"name": "sunny",
	"age": 3
}

5. You can see the response in the bottom of the page.

3. Update or POST

1. Open Postman
2. Select POST as protocol and http://localhost:5000/pets/1 as URL
3. Configure the headers to send JSON data by making key as Content-Type and value as application/json.
4. Send sample test data in body.

Sample test data:

{
	"name": "mypuppy",
	"age": "10"
}

5. You can see the response in the bottom of the page as updated successfully.

4. Delete

1. Open Postman
2. Select DELETE as protocol and http://localhost:5000/pets/1 as URL and click Send.
3. You can see the response in the bottom of the page as deleted successfully.