Web Technology Experts Notes

Thursday, 22 June 2017

setup of EJS template in Express? Get/Set session in Express? How to setup static path in Express

Question: What is res.sendFile() in NodeJS?
It is a simple way to deliver an HTML file to the client.

Example of sendFile

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

app.get('/', function(req, res) {
    res.sendFile(path.join(__dirname + '/index.html'));
});
app.listen(8080);

Question: How to use EJS in Express?
Install the EJS

npm install ejs --save

Set the Engine as EJS in node server

app.set('view engine', 'ejs');

render file from node server

app.get('/', function(req, res) {  
  res.render('index', { title: 'The index page!' })
});

Use the parameter in File

<%= title %>

Question: How to Get/Set session in Express?
install session

npm instal express-session --save

Initiaization the session

var session = require('express-session');
app.use(session({
    secret: 'SECRETKEY',
    name: 'SESSION NAME',
    proxy: true,
    resave: true,
    saveUninitialized: true
}));

Set the Session

var sessionData
app.get('/set-the-session', function(req, res) {    
    sessionData = req.session;
    var userDetails = {}    

    //set the session
    sessionData.isLogin = 1;
    sessionData.name = req.body.name;
    sessionData.email = req.body.email;
});

Get the Session

app.get('/get-session', function(req, res) {    
    sessionData = req.session;
    userDetails.isLogin = sessionData.isLogin;
    userDetails.name = sessionData.name;
    userDetails.email = sessionData.email;
    res.send(userDetails);    
});

Question: How to setup static path in Express?

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

create file in : images/kitten.jpg, Now you can access

http://localhost:3000/images/kitten.jpg

Question: Session is not working with ajax call
Explanation
URL: http://127.0.0.1:8080/getphotoaccess?uid=7177
When running in browser, session is working fine.
When running with ajax call, session is not working

Solution
You need to add xhrFields: {: true},in ajax request.
For Example:

$.ajax({
    type: "GET",
    url: "getphotoaccess?uid=7177",            
    dataType: "json",    
    xhrFields: {
            withCredentials: true
       },            
    success: function(resData){

    }
});

Tuesday, 20 June 2017

Socket.IO module with nodeJs tutorial

How to send message from Node(server) to browser(client) and vice versa? How to connect/disconnect to the room.

Question: What is socket.io module?
Socket.IO is a JavaScript library for realtime web applications.
It enables realtime, bi-directional communication between web clients and servers.
It has two parts
a) client-side library that runs in the browser.
b) server side that run in browser.

Question: Give example of real time application?

Instant messengers like facebook notification/message.
Push Notifications like when someone tags you in a picture on facebook, you receive an instant notification.
Collaboration applications like multiple user editing same file.
Online gaming

Question: Why we use socket.io?

bi-directional communication channel between a client and a server.
When an event occur, socket get notify and let to know the single client OR all clients.
It is trust application and used by Microsoft Office, Yammer, Zendesk, Trello, and numerous other organizations.

Question: How to install socket.io in Web and Server?
In Browser (client)

<script src="https://cdnjs.cloudflare.com/ajax/libs/socket.io/2.0.3/socket.io.js"></script>

In NodeJS

npm install socket.io

var io = require('socket.io')

Question: How get to know, if user is connect/disconnect?
In Server(Node)

var app = require('express')();
var http = require('http').Server(app);
var io = require('socket.io')(http);

app.get('/', function(req, res){
  res.sendfile('index.html');
});

//Whenever someone connects (execute when come in Web page)
io.on('connection', function(socket){
  console.log('A user connected');

  //Whenever someone disconnects (execute when Leave the web page)
  socket.on('disconnect', function () {
    console.log('A user disconnected');
  });

});

http.listen(3000, function(){
  console.log('listening on *:3000');
});

In Browser

 var socket = io.connect('http://127.0.0.1:3000');

Question: How to get to know, when new user comes in browse?

OR
Question: How to send message from Client(Browser) to Server(Node)?
In Server

 
socket.on('adduser', function(name, email, uid) {
    //name, email, and uid of user
    console.log('New user comes in web page');
});

In Browser>

 
socket.emit('adduser', 'Robin Sharma','robinsharma@no-spam.ws',2555);

Question: How to send message from Server(Node) to Client(Browser)?
In Server

socket.emit('newRequestCome', 'name','myself send request'); //Send message to socket (Same window)
socket.broadcast.to(roomName).emit( 'newRequestCome','name','message'); //Send message to all socket (Other windows in same Room)

In Browser

 
socket.on('newRequestCome', function(name, message) {                        

});

Question: How to join the room and send message?
Join the room

io.on('connection', function(socket){
  socket.join('someNo12');
});

Question: How to send message the room?
Send message to the room

io.in('someNo12').emit('some event');
//io.to('someNo12').emit('some event');

Thursday, 22 June 2017

Express JS - use res.sendFile - use EJS template - Set and Get Session data

Best Related Posts are Following:

Tuesday, 20 June 2017

Socket.IO module with nodeJs tutorial

Best Related Posts are Following: