NodeJS Interview Questions

1) How to access the Windows Environment Variables programmatically via NodeJS?

The process.env will provide the required functionality.

  process.env.HOME

  process.env.HOMEPATH

 

In order to have this dynamically we can have

 

  var  nodePath = 'NODE_PATH';

  process.env[nodePath];

 

2) What is async and await in NodeJS?

async à in simple terms marks the function to run asynchronously

await à Marks the caller to wait until the function executes.

3) How to create a directory in NodeJS?

 

  var fileSystem = require('fs'); 

  var DIR_NAME = 'test';

 

  if(!fileSystem.exists(DIR_NAME)){

    fileSystem.mkdir(DIR_NAME);

  }

 

4) How to use jQuery in NodeJS?

We need to install jQuery via npm then use it as follows

npm install jquery

Usually point it to $ by

var $ = require('jquery');

 Sometimes we need to install the jsdom also to get the handle of the window

npm install jsdom

 

5) How to call a function / method from another file in NodeJS?

Using the module.exports

For example if we want to call a function checkServiceAvailablity from the service httpService.ts

Steps:

// in httpService.ts

module.exports =

{

checkServiceAvailablity: function(serviceName:any){

// For example, returning true

return true;

}

    };

 

In the desired page

Require it in the top

Then call it in the code

    // In the desired place

    var httpServ = require('../httpService.ts');

    

    if(httpServ.checkServiceAvailablity('REST_SERVICE_PATH')){

        // Do action

    }else{

        // Throw error : Service not available

    }

 

 6) What is CJS and ESM?

CJS à Common JS

ESM à ECMA Script Modules

NodeJs is written in CJS

7) What is –save option?

--save or --s option is no longer needed from npm V5.0

By default, without the save option the npm will save all the dependencies automatically without any explicit instruction.

(Last Update on 18-August-2021)