Showing posts with label ExpressJs. Show all posts
Showing posts with label ExpressJs. Show all posts

Tuesday 12 September 2017

How to create an HTTPS server in Node.js?

How to create an HTTPS server in Node.js?

Question: Run Node with http?
var express = require('express');
var app = express();

//Include modules
var http = require('http').Server(app);
var io = require('socket.io')(http);


http.listen('8082', function() {
    console.log('http listening on *:8082');
});

You can run as http://localhost:8082


Question: What certificate you require for https?
  1. server.key
  2. server.crt
  3. Create a folder public/cert at root of your project and add above 2 files.



Question: Run Node with https?
var express = require('express');
var app = express();

//Include modules

var https = require('https');
fs = require('fs');


var privateKey = fs.readFileSync('public/cert/server.key', 'utf8');
var certificate = fs.readFileSync('public/cert/server.crt', 'utf8');
var credentials = {key: privateKey, cert: certificate};
var httpsServer = https.createServer(credentials, app);
var io = require('socket.io')(httpsServer);

httpsServer.listen('8083', function() {
    console.log('https listening on *:8083');
});
 

You can run as https://localhost:8083



Thursday 13 July 2017

Express JS Interview Questions and Answer for 1 Year Experienced

Express JS Interview Questions and Answer for 1 Year Experienced

Question: What Are Core Features Of Express Framework?
  1. Allows to set up middlewares to respond to HTTP Requests.
  2. Defines a routing.
  3. Dynamically render HTML Pages



Question: Why I Should Use Express Js?
It is light-weight server side web application framework which work on node.js platform.


Question: How to get The full Url In Express?
var port = req.app.settings.port || cfg.port;
res.locals.requested_url = req.protocol + '://' + req.host  + ':'+port + req.path;



Question: How to download a file?
app.get('/download', function(req, res){
  var file = __dirname + '/myfile/download.txt';
  res.download(file); 
});



Question: How To enable debugging In Express App?
In windows
set DEBUG=express:* & node index.js

In Linux
DEBUG=express:* node index.js


Question: How to render plain Html?
res.sendFile();
res.render();


Question: How to use handle get request in express Js?
var app = require('express')();
var http = require('http').Server(app);

app.get('/listing', function (req, res) {   
   res.send('This is listing API'); 
});

http.listen('8080', function() {
    console.log('listening on *:8080');
});



Question: How to receive get parameter in Express Js?
app.get('/listing', function (req, res) {   
    console.log(req.query);   //Receive get data
});



Question: How to receive post parameter in express Js?
app.post('/listing', function (req, res) {   
    console.log(req.body);   //Receive post data
});



Question: What is Callback in node.js?
Callback function is used in node.js to deal with multiple requests made to the server. Node is single thread based application and works on the behalf of events.


Question: How to send Ajax call in NodeJS?
Install the request
npm install request

request = require('request');
request( "http://exmaple.com:8081:/users/login/?username=testing@no-spam.ws&password=73278342", function(err, res, body) {                    
          console.log(res.console);          
      });



Question: How to get cookies in expressJs?
npm install cookie-parser
var express = require('express');
var app = express();

var cookieParser = require('cookie-parser');
app.use(cookieParser());

app.get('/listing', function (req, res) {   
    console.log(req.cookies);    
});



Question: What are different methods in REST API?
  1. GET : Used to read.
  2. POST: Used to update.
  3. PUT: Used to create.
  4. DELETE: Used to delete



Question: List out some REPL commands in Node.js?
  1. Ctrl + c - For terminating the current command.
  2. Ctrl + c twice – For terminating REPL.
  3. Ctrl + d - For terminating REPL.
  4. Tab Keys - list of all the current commands.
  5. .break - exit from multiline expression.
  6. .save with filename - save REPL session to a file.



Question: How you can update NPM to new version in Node.js?
sudo npm install npm -g



Question: What do you mean by "Callback hell"?
"Callback hell" is referred to heavily nested callbacks which has become unreadable.


Question: What are "Streams" in Node.JS?
Streams are objects which will let you read the data from source and write data to destination as a continuous process.


Question: What you mean by chaining in Node.JS?
It's a mechanism in which output of one stream will be connected to another stream and thus creating a chain of multiple stream operations.


Question: What is the use of method – spawn()?
This method is used to launch a new process.
child_process.spawn(command[, args][, options])



Tuesday 11 July 2017

Express JS Interview Questions and Answer for experienced

Express JS Interview Questions and Answer for experienced

Question: What is meaning of app.get(*) in express js?
app.get(*) means that for any GET request not already handled yet, will come in this route.
Note: this must be at the end of all route handling (Last route).

See example below:
//Login route
app.get('/login', function(req,res){ /*Login code */ });

//Register route
app.get('/register', function(req,res){/*Register code */});

//Route which is not handled yet
app.get('*', function(req, res, next) {
  var err = new Error();
  err.status = 404;
  next(err);
}

As we know, last route is for not found route, So in this we have set the status 404.
and pass the error object to the next.
When we call next() without parameter, then it run next middleware.
When we call next() with parameter, then it run differently.


Question: What is use of next() in express JS?
next is an argument provided by Express.js as a way to "pass along" control to the next middleware (or route).


Question: What is Middleware?
Middleware are functions that have access to the request object (req), the response object (res), and the next middleware function in the application's request-response cycle.
The next middleware function is commonly denoted by a variable named next.


Question: What are benefits of Middleware?
  1. Execute any code.
  2. Make changes to the request and the response objects.
  3. End the request-response cycle.
  4. Call the next middleware function in the stack.



Question: What are different Middleware?
  1. Application-level middleware
    app.use(function (req, res, next) {
      console.log('Time:', Date.now())
      next()
    })
  2. Router-level middleware
  3. Error-handling middleware
  4. Built-in middleware
  5. Third-party middleware



Question: How to setup log4js?
Install log4js
npm install log4js

Include log4js
//include the log4js file
var log4js = require('log4js');

Configure log4js
//Configure the log4js
log4js.configure({
  appenders: { 
      display: { type: 'stdout' },
      file: { type: 'file', filename: './data/chat_logs.log' }
  
    },
  categories: { 
      display: { appenders: ['display'], level: 'debug' },      
      file: { appenders: ['file'], level: 'debug' },
      default: { appenders: ['display'], level: 'debug' }
      
  }
});

Display log4js in console
var Logger = log4js.getLogger('display'); 

Logger.trace('this is message1');
Logger.info('this is message2');
Logger.warn('this is message3');
Logger.error('this is message4');
Logger.debug('this is message5');
All the data will display in console


Question: How to store the logs in file?
var Logger = log4js.getLogger('file'); 

Logger.trace('this is message1');
Logger.info('this is message2');
Logger.warn('this is message3');
Logger.error('this is message4');
Logger.debug('this is message5');




Thursday 6 July 2017

Node Js Interview Questions and answer for Experienced

Node Js Interview Questions and answer for Experienced

Question: What is objectId in MongoDB?
It is 12 byte object consist of following
  1. a 4-byte value representing the seconds since the Unix epoch
  2. a 3-byte machine identifier
  3. a 2-byte process id
  4. a 3-byte counter, starting with a random value.



Question: How to get timestamp from objectId?
ObjectId.getTimestamp();



Question: What is difference between npm install vs npm update?
npm install:
1. installs all modules that are listed on package.json file and their dependencies.
2. module without version mention in package.json, npm install will be ignore if already installed.

npm update:
1. updates all packages in the node_modules directory and their dependencies.
2. module without version mention in package.json, will update to latest version (If not then installed the latest version).


Question: How to set npm start with start the application?
  1. Open package.json which is located on root.
  2. Add following code in package.json (If not added)
      "scripts": {
        "start": "node index.js"
      }
    

    Please repace "index.js" with your application file.
  3. Now, you can run npm start from command console.



Question: How to destroy the session in node?
You can use req.session.destroy(), See Exampe below:
exports.logout = function(req, res) {        
    req.session.destroy();
    res.send({logout:1});
}



Question: How to redirect to 404 errors page in ExpressJS?
After difining all the URL route, add the following code
app.use(function(req, res, next) {
    res.status(404).json({errorCode: 404, errorMsg: "route not found"});
});

When someone trying to access not available pages, it will show 404 error code.


Question: What is CORS?
Cross Origin Resource Sharing.


Question: What use use of CORS?
Suppose your are website is at mywebiste.com and want to access the javascript/API which is on mywebiste2.com. You can't access the data/api from mywebiste2.com unless they allow you. This is known as Cross Origin Resource Sharing.


Question: How we can achieve CORS?
Add the following code in your node application, it will allow everyone to access your code. In Access-Control-Allow-Origin, you can specify the domain name.
app.use(function(req, res, next) {
  res.header("Access-Control-Allow-Origin", "*");
  res.header("Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, Accept");
  next();
});



Question: What do you mean by Asynchronous API?
All APIs of Node.js library are aynchronous, means all are non-blocking.


Question: What is package.json?
package.json is present in the root directory of any Node application/module and is used to define the properties of a package.


Question: What is Piping in Node?
Piping is a mechanism to connect output of one stream to input of another stream. It means get data from one stream and to pass output of that stream to another stream and there is no limit to piping operations.


Question: What is Callback in node.js?
Callback function is used in node.js to deal with multiple requests made to the server. Node is single thread based application and works on the behalf of events.


Monday 3 July 2017

Express Js routing example - GET/POST/PUT

Express JS Routing - Understanding GET/POST/PUT with parameter

Question: Give example of express JS working with Node?
var express = require('express');
var app = express();

var bodyParser = require('body-parser')
app.use(bodyParser.json());  
app.use(bodyParser.urlencoded({
    extended: true
}));

app.get('/', function(req, res){
  res.send('id: ' + req.query.id);  
});
app.listen(3000);



Question: What is use of body-parser?
It is middleware in nodeJS.
body-parser is used to parse incoming request bodies, available under the req.body property.



Example-1: URL / with Get Method.
app.get('/', function (req, res) {
  res.send('Hello, this is Home page.')
})



Example-2: URL /about with Get Method.
app.get('/about', function (req, res) {
  res.send('You have called /about with get method.')
})



Example-3. URL /senddata with POST Method.
app.post('/senddata', function (req, res) {
    //req.body have all the parameter
   console.log(req.body);
  res.send('Hello, Received post data request.')
})



Example-4: Routing with Regex 
app.get('/ab?cd', function (req, res) {
  res.send('ab?cd')
})

This route path will match acd, abcd.


Example-5: Routing with Regex
app.get('/ab+cd', function (req, res) {
  res.send('ab?cd')
})
This route path will match abcd, abbcd, abbbcd, and so on.



Example-6: Routing with dynamic parameter 
app.get('/users/:userId/books/:bookId', function (req, res) {
  console.log(req.params);
   res.send('Received the request for /users/10/book/12222');
});

Request URL: http://localhost:8080/users/10/books/12222


Example-7: Routing with dynamic parameter - Example 2
app.get('/messages/:from-:to', function (req, res) {
  console.log(req.params);
   res.send('Received the request for /messages/10-100');
});

Request URL: http://localhost:8080/messages/10-1000


Question: How to send request with all methods i.e GET/POST/PUT
app.all('/messages/list', function (req, res) {  
   res.send('Work for all type of request');
});