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])

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