Interview Questions

AJAX Interview Questions Android Interview Questions Angular 2 Interview Questions AngularJs Interview Questions Apache Presto Interview Questions Apache Tapestry Interview Questions Arduino Interview Questions ASP.NET MVC Interview Questions Aurelia Interview Questions AWS Interview Questions Blockchain Interview Questions Bootstrap Interview Questions C Interview Questions C Programming Coding Interview Questions C# Interview Questions C++ Interview Questions Cakephp Interview Questions Cassandra Interview Questions CherryPy Interview Questions Clojure Interview Questions Cobol Interview Questions CodeIgniter interview Questions CoffeeScript Interview Questions Cordova Interview Questions CouchDB interview questions CSS Buttons Interview Questions CSS Interview Questions D Programming Language Interview Questions Dart Programming Language Interview Questions Data structure & Algorithm Interview Questions DB2 Interview Questions DBMS Interview Questions Django Interview Questions Docker Interview Questions DOJO Interview Questions Drupal Interview Questions Electron Interview Questions Elixir Interview Questions Erlang Interview Questions ES6 Interview Questions and Answers Euphoria Interview Questions ExpressJS Interview Questions Ext Js Interview Questions F# Interview Questions Firebase Interview Questions Flask Interview Questions Flex Interview Questions Fortran Interview Questions Foundation Interview Questions Framework7 Interview Questions FuelPHP Framework Interview Questions Go Programming Language Interview Questions Google Maps Interview Questions Groovy interview Questions GWT Interview Questions Hadoop Interview Questions Haskell Interview Questions Highcharts Interview Questions HTML Interview Questions HTTP Interview Questions Ionic Interview Questions iOS Interview Questions IoT Interview Questions Java BeanUtils Interview Questions Java Collections Interview Questions Java Interview Questions Java JDBC Interview Questions Java Multithreading Interview Questions Java OOPS Interview Questions Java Programming Coding Interview Questions Java Swing Interview Questions JavaFX Interview Questions JavaScript Interview Questions JCL (Job Control Language) Interview Questions Joomla Interview Questions jQuery Interview Questions js Interview Questions JSF Interview Questions JSP Interview Questions KnockoutJS Interview Questions Koa Interview Questions Laravel Interview Questions Less Interview Questions LISP Interview Questions Magento Interview Questions MariaDB Interview Questions Material Design Lite Interview Questions Materialize CSS Framework Interview Questions MathML Interview Questions MATLAB Interview Questions Meteor Interview Questions MongoDB interview Questions Moo Tools Interview Questions MySQL Interview Questions NodeJS Interview Questions OpenStack Interview Questions Oracle DBA Interview Questions Pascal Interview Questions Perl interview questions Phalcon Framework Interview Questions PhantomJS Interview Questions PhoneGap Interview Questions Php Interview Questions PL/SQL Interview Questions PostgreSQL Interview Questions PouchDB Interview Questions Prototype Interview Questions Pure CSS Interview Questions Python Interview Questions R programming Language Interview Questions React Native Interview Questions ReactJS Interview Questions RequireJs Interview Questions RESTful Web Services Interview Questions RPA Interview Questions Ruby Interview Questions Ruby on Rails Interview Questions SAS Interview Questions SASS Interview Questions Scala Interview Questions Sencha Touch Interview Questions SEO Interview Questions Servlet Interview Questions SQL Interview Questions SQL Server Interview Questions SQLite Interview Questions Struts Interview Questions SVG Interview Questions Swift Interview Questions Symfony PHP Framework Interview Questions T-SQL(Transact-SQL) Interview Questions TurboGears Framework Interview Questions TypeScript Interview Questions UiPath Interview Questions VB Script Interview Questions VBA Interview Questions WCF Interview Questions Web icon Interview Questions Web Service Interview Questions Web2py Framework Interview Questions WebGL Interview Questions Website Development Interview Questions WordPress Interview Questions Xamarin Interview Questions XHTML Interview Questions XML Interview Questions XSL Interview Questions Yii PHP Framework Interview Questions Zend Framework Interview Questions

Top 15 ExpressJS Interview Questions for 2022

1) What is ExpressJs?

Express Js is a framework for node.js which is light-weight and fast. It is used to develop web and mobile applications.

2) What are the features of ExpressJs?

Following are the features of Expressjs:
  • It allows middleware set up to respond HTTP Requests
  • It defines routing table which is used to achieve action based on HTTP Method and URL.
  • It allows dynamically generate the HTML Pages based on passing arguments to the templates.
  • It follows MVC architecture for web application.

3) What is middleware in ExpressJs?

Middleware is a function that accesses the request object (req), response object (res), and access next middleware function in application's request-response cycle. The next middleware function is represented by variable called 'next'. Syntax:
function(req,res,next){ }

4) Can middleware is able for error handling? Explain error handling in ExpressJs.

Middleware is able to handle error handling in ExpressJs. This can be done by passing one extra error-handling (err) parameter in middleware function. Syntax:
function(err,req,res,next){ }

5) What is 'next' in ExpressJs?

'next' is a parameter which is passed in middleware function to pass control to next middleware.
function(req,res,next){ }

6) What is routing?

Routing define how an application responds over client request to a particular endpoint (URI). Endpoint is specially a path and any one of HTTP request methods (GET, POST, etc). Following structure is used for routing: app.METHOD(PATH,HANDLER)

Note: METHOD is Http request method (in lowercase),

PATH is uri on server, HANDLER is function name.

7) How to configure properties in ExpressJs application?

We can configure properties in two ways:
    • With Process.env.
      • Create a file with extension '.env' inside the project folder.
      • Add all the properties in '.env' file.
      • In server.js any of properties can use:
var host=process.env.APP_HOST;  

app.set('host',host);  

logger.info(app.get('host');
  • With RequireJs.
Create a file 'config.json' inside 'config' folder of the project folder.

Add config properties in 'config.json' file.

Use require keyword to access the 'config.json' file.
var config =require('./config/config.json');

8) How debugging are done in ExpressJs?

Different operating system uses different commands:
Windows: set DEBUG = express:* & node index.js

Linux: $ DEBUG = express:* & node index.js

9) Define templating in ExpressJs?

Templating are powerful engine used for removing the cluttering of our server code with HTML. Some of the templates which are with ExpressJs are:
  • Pug
  • Mustache
  • EJS

10) What is cookie and what it does?

Cookie is a data sent from server and stores on the client side. It keeps the information of user's actions. These are some following purpose of using cookie:
  • Session management
  • User tracking
  • Personalization

11) How to use cookies in ExpressJs?

Cookies are used in ExpressJs by installing 'cookie-parser' middleware. To install cookie-parser we use command as:
npm install --save cookie-parser
To set new cookie in our application, we define a new route.  

app.get('/',function(req, res){  

res.cookie('name','express').send('cookie set')  

});

12) How to delete cookie in ExpressJs?

The clearCookie method is used to delete cookies in ExpressJs.
clearCookie('cookie_name');
app.get('/clear_cookie_temp',function(req,res)){  

        clearCookie('temp');  

    res.send('cookie temp is cleared');  

    });

13) How to handle 404 errors or redirect error to another page?

We use the following code in server.js file to redirect 404 errors to another page in ExpressJs.
app.use(function(req, res, next){  

    res.status(404).json({errorCode: 404, errorMessage: requested resources not found”});  

});

14) What is scaffolding?

Scaffolding is a tool, which set up all required public directory, add middleware, create separate route file etc (set up skeleton for web application). So that we can directly get started building our application. Yeoman is scaffolding tool built for Node.js.

15) How to get the full url In ExpressJs?

var port = req.app.settings.port || cfg.port;  

res.locals.requested_url = req.protocol + '://' + req.host  + ( port == 80 || port == 443 ? '' : ':'+port ) + req.path;



ADVERTISEMENT
ADVERTISEMENT