Web Develpers era

how to use another page urls from running page and how to create router |, rest api ain nodejs nodejstututorials

u already seen this below code in above programms or previus posts

create router folder

in thgat create productRouter.js

const express = require('express');
const app = express();
var mongoose= require("mongoose");
var Persons=require("../models/personSchema,js");

var productRouter = express.Router();

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

productRouter.use(bodyParser.json());

productRouter.route('/')
.get(function (req,res)
{
    Persons.find({}, function(err,person)
    {
        if(err) throw err;
        res.json(person);
        
    })
 
})

module.exports= productRouter;

in index.js

import and use this file

var productRouter = require('./router/productRouter');

use

app.use('/products', productRouter);

http://localhost:3000/products/

if u hit this api - u can get

all the things in product page

statemanagement in nodejs | nodejs tutorials

staetemenage storing cooking to identify users

state management 
one client make request with web form
client requested data send to backend
then it will responds 
but requested data not tehre
to store taht data 
we use statemanagement

we will use different type of module to use statemanagement

sm has two major parts
client side- client side manage management
server side- it is called as servr side management

client side - cookies
serverside - sessions

stored to browser cokokie

i not entered any expiry data

so it will remove automatically whenever browser closed

in below programm set the cookie and remove the cookie

var express = require('express');
var cookieParser = require('cookie-parser');

var app = express();
app.use(cookieParser());

app.get('/', 
function (req,res)
{
    res.cookie('mycookie', 'tutorials point video tutorials');
    res.end('hi there');
}

);

app.get('/remove', 
function (req,res)
{
    res.clearCookie("mycookie");
    res.end('hi there');
}

);

app.listen(8081,
    function () {
       console.log("server started");
    });

encrypt cookie

app.use sesion - secret - encryt, save initialise- if u not do any change in cokokie in their time it will be like original

when login is done - it will false

max age is 60000 milli seconds

var express = require('express');
var cookieParser = require('cookie-parser');
var session= require("express-session");
var morgan = require("morgan");

var app = express();

app.use(morgan('dev'));
app.use(cookieParser());
app.use(session({secret: 'secretkey', saveUnitialised:true, resave: true, cookie: {maxAge: 60000}}));

app.get('/', 
function (req,res,next)
{
   if(req.session.views)
   {
        req.session.views++;
        res.setHeader('Content-Type','text/html')
        res.write('<p> views:' + req.session.views +'</p>')
        res.write('<p> expires in:' + (req.session.cookie.maxAge / 1000) +'</p>')
        res.end()
   }
   else {
    req.session.views=1
    res.end('refresh page')
   }
}

);

app.listen(8081,
    function () {
       console.log("server started");
    });

ist prints in browser

prints

refresh

after refresh

taht count increses

after one idle minute - no refresh - session expires

it will show refresh

nodejs middlewares | nodejs tutorials

with use we can use middleware

in below

code

middleware- whenever before process actualt request - middlewre acts as mediator - if it passes

whenever reaches home url

it calls log and hello function

because it ats as middleare in this

when log call bcak function it printes log

when hello function it prints hello

next means - go back to api , after log , calls next middleware

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

app.get("/", log, hello);

function log(req, res, next)
{
    console.log("log started");
    next();
}
function hello(req, res, next)
{
    console.log("hello started");
    next();
}

app.listen(8081,
    function () {
       console.log("server started");
    });

node js get and post request from html page | nodejs tutorials

const express = require('express');
const app = express();
app.use(express.static('public'));

public means

//use method will be use whenever wanna make middlewares im our applications, middlewares will be used before responding requiest (mediator between request and before respond)
//routing ist auth - then controler - in auth is mediatior
// we create a folder called public, inside this we will place a style sheet, javascrpt, fonts, images we will place at public

one seperate directory for images,javascript files, css file that called as scaffolding

npm install express-generator -g

to make public folders

get api with star

app.get("/*list",(req,res,next) =>
{
  let person="department listing"
res.send(person);
}
);

personlist or any thing before list

api process_get

json stringfy - combine response

app.get("/process_get",(req,res,next) =>
{
  response=
  {
    first_name :req.query.first_name,
    last_name :req.query.last_name
  };
  res.end(JSON.stringify(response));

}
);

post api

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

var urlencodedParser= bodyParser.urlencoded({ extended: true });

post api needs url encoded and body-parser

urlencodedParesr - is like middleware

before api

app.post("/process_post",urlencodedParser,
function (req,res)
{
  response=
  {
    first_name :req.body.first_name,
    last_name :req.body.last_name
  };
  res.end(JSON.stringify(response));

}
);

post is from aoi or html form

api get form

app.get("/form",(req,res,next) =>
{
  
  res.sendFile(__dirname + "/" + "one.html");

}
);

one.html

<form method="POST" action="http://localhost:8081/process_post">

    <input type ="text" name="first_name">
    <input type ="text" name="last_name">
    <input type="submit" name="submit">
</form>

after submit post in above html form

it will reach process_post

takes taht data from post data and combine as stringify

connect to server

using below

var server = app.listen(8081,
    function () {
        var host= server.address().address;
        var port= server.address().port;
        console.log("listening at http://%s:%s", host,port);
    });

node js network programming | nodejs tutorials

tcp

node js server programming using tcp

on socket - we will host our applicaitons

and at the other end on telnet - we wil raise request

telnent transfered by tcp to socket - raise teh request - resolve at asocket

for this purpose we import net

create a server with socket

server.js

var net = require("net");
console.log('vamsi');
var server = net.createServer(function(socket)
{
    socket.end("Hello and good bye");
}

);

server.on("error", function(error){
    if(error.code ==='EADDRINUSE')
    {
        console.error("port is already in use");
    }
})
server.listen(1234, function (){
    console.log("server started");
});

if server is on

it below programm run otherwise port is not running like that areror displays

var net = require("net");

var client = net.connect(
    {
        port :1234,
        host: "localhost",
    }, function (){
        console.log("connection establieshd");
    }
    
);

client.js

conenct to port 1234

in bleow programming

after server started

connected print

then at aclient side write json messange on client side

if any change in file modfication time

fs.watch - it watch continuosly

if modified - write

changed into file

if client is disconnected it will print disconected

fs.watch

connectin.write

connection.on

server.js

run node server.js data.txt

it will write int data.text

file

node client.js

write into file

echo >>data.txt

conect between client and server

node js filestream | node js tutorials

_filename

_dirname

above are two glabal varialbe

_dirname - it prints current directoru

_filename - it printes current location

process.cwd()

current working directory

process.chdir("") change directory

join path and string

path.sep = console = /

directories.join(path.sep);

how to base name from path

how to get ext from path

path.extname(filename)

path.basename(filename)

how to get absolute path

path.resolve(_dirname,'content','subfolder','test.txt')

users/smilga/desktop/tutorial/content/subfolder/test.txt

how to check file exists and

red file write file then rename the file

fs is one module

var fs= require('fs');

var path= _dirname +"/mytext.txt";

fs.readFile(path, "utf8" function(error,data)

read the file in that path and then encrypt with utf8 then callback the function

how to rename the fuile

fs.rename

make new directory

read all the data in directory

fs.readdir(path, function (error,files){

remove directory

fs.rmdir

const {readFileSync,writeFileSync} = require('fs');

read the file

const first = readfilesync('pathname','utf8');

write into file

write from another files too

writefilesync('path','hellow world : ${first}, ${second}',{flag:'a'})

flag new line

flag a means append

create server , console the data from file

it wil print the whole data its in mbs if it is a larage file

fs.craetereadstream

same size in ui but in response headers , transfer-encoding - chunked

readfile('path',(){})

call back function with arguments
readfile('path',(err,result){

if(err)

{

console.log(err)

return

}

console.log(result)

})

without utf8

readfile('path','utf8',(err,result){

if(err)

{

console.log(err)

return

}

console.log(result)

const first : result

writeFIle('path','here $(furst)',(err,resulte)=>{})

})

write file

read and write into same file

whats the difference between read file and read file sync

if async- if a function takes time - taht function execute late, whichone execute first that one wil execute

before excute of readfiile sync console works

but line by line works which one take large time that throw to last time means it runs on sepaerately

if it works over it prints immedieatly

next line not stop for before line

sync

async

readFile

with promise

now below works as sync

means when this called it must return becaue of promise (call back)

till that next line waits

const start = async() => {}

call back in async funciton

const start = async() => {

const first = await getText('./content/first.txt');

console.log(first);

}

in try catch

one function for number of file paths

const start = async() => {

try{

const first = await getText('./content/first.txt');

const second = await getText('./content/second.txt');

console.log(first);

}catch(error)[

console.log(error)

}

calling above function - invoke

start();

instead of writing get text function seperate use

util

util is a ibuilt funciton

without util and with promises

in above thing, if read one file that file data write to another fileif the next funciton in next line , its not wokrs because it is async

so for that purpose in call back we write another funciion like below

node js eror handling

in normal programing we willl use try catch

but in node js different

including a domain module

whatever programmin gin domain module

if any error caught - it will print

get one from mongodatabase using node js via api | nodejs tutorails

get one usng findone

app.get('/get-one-await',async (req, res)=> {
  let params = req.query.id;
  let listDetails= await PERSON_SCHEMA.findOne({id:params}).sort({_id:-1});
  res.send(listDetails);
    
})

app.get('/get-by-id',async (req, res)=> {
  let body = req.body;
  PERSON_SCHEMA.find({fname: {$eq: body.name}}).then(result =>
    {
      res.send(result)
    }).catch(err => {
      res.send("faile")
    })
    
    
})

app.get('/get-by-id-one',async (req, res)=> {
  let body = req.body;
  PERSON_SCHEMA.findOne({fname: {$eq: body.name}}).then(result =>
    {
      res.send(result)
    }).catch(err => {
      res.send("faile")
    })
    
    
})

http://localhost:3000/get-by-id-one

get data from databse using api and mongo db | nodejs tutorials

api

http://localhost:3000/get

app.get('/get',async (req, res)=> {

  PERSON_SCHEMA.find().then(result =>
    {
      res.send(result)
    }).catch(err => {
      res.send("faile")
    })
    
})

app.get('/get-await',async (req, res)=> {

  let listDetails= await PERSON_SCHEMA.find({});
  res.send(listDetails);
    
})

how to insert multiple records using post man api| nodejstutorials

using below method

u can insert many records at a time using one api

create many api

app.post('/create-many',async (req, res)=> {
  let body = req.body;

  PERSON_SCHEMA.insertMany(body).then(result =>
    {
      res.send({sts:200,msg:'created'})
    }).catch(err => {
      res.send("faile")
    })
    
})

post man data

api http://localhost:3000/create-many

[

    {
  "fname": "one",
  "lname": "onel",
  "mno": "one mobile",
  "addr": "one addr"
},
{
    "fname": "two",
    "lname": "twol",
    "mno": "two mobile",
    "addr": "two addr"
  },
  {
    "fname": "two",
    "lname": "twol",
    "mno": "two mobile",
    "addr": "two addr"
  },
  {
    "fname": "two",
    "lname": "threel",
    "mno": "three mobile",
    "addr": "three addr"
  }
]

hit on api it willl insert into databse

how to install mongodb compass in ubuntu 20.04| mongodb nodejs tutorials

wget https://downloads.mongodb.com/compass/mongodb-compass_1.21.1_amd64.deb
sudo dpkg -i mongodb-compass_1.21.1_amd64.deb
sudo apt --fix-broken install
mongodb-compass

this is the screen visible after sucesful install of mongodb compass

then

check mongodb status

 sudo service mongodb status



u canc heck in above screen shot it is active and running

if not start the mongodb

u can see the screen  of mongo db compass , in that see connect button

click on connect button if server is running

if not run the server or give the credentials of onliine server which is running

connected succefully

if u have credentials to connect past in below window

how it gets->

it wil shwo whats tables or databses u have already

refresh taht databse if u wanna see updated