Cognizant – Node JS Interview Questions

Here is the list of Node JS Interview Questions which are recently asked in Cognizant company. These questions are included for both Freshers and Experienced professionals. Our Node JS Training has Answered all the below Questions.

1. Explain What is NPM ?

NPM-Node Package Manager is a package manager for the JavaScript programming language maintained by NPM, Inc.js. It consists of a command line client, also called NPM and an online database of public and paid-for private packages, called the NPM registry.

2. Explain Modules in Node Js ?

Module in Node JS is a simple or complex functionality organized in single or multiple JavaScript files which can be reused throughout the Node JS application.

3. What are CommonJs Modules ?

CommonJS module is a reusable piece of JavaScript that exports specific objects made available to any dependent code. Unlike AMD, there are typically no function wrappers around such modules.

4. For what require() is used in Node Js ?

require() isa built-in function with a special purpose used to load modules. Modules are a way to split an application into separate files instead of having all of your application in one file.

5. Explain module.exports in Node Js ?

Export is a special object which is included in every JavaScript file in the Node JS application by default. The module is a variable that represents the current module, and export is an object that will be exposed as a module. So, whatever assigned to module.exports, it will be exposed as a module.

6. Is Node Js Single-threaded ?

Node JS is single-threaded similar to JavaScript. So, the JS code is running in a single thread(main thread) in consensus with the event loop and callback queue.

7. What are events ?

Much of the Node JS core API is built around an idiomatic asynchronous event-driven architecture in which certain kinds of objects called "emitters" that emits named events that cause Function objects to be called.

8. Explain event loop in Node Js ?

The event loop is what allows Node JS to perform non-blocking I/O operations — despite the fact that JavaScript is single-threaded — by offloading operations to the system kernel whenever possible. Since most modern kernels are multi-threaded, they can handle multiple operations executing in the background.

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9. How to create a simple server in Node js that returns Hello World ?

To get started with a Node JS web application, initialize the project in the project folder on terminal. Open a terminal window and create a new directory called simple_server with mkdir and Initialize the project with npminit.

10. Difference between cluster and child_process modules?

With the cluster module, the creation and sharing of child processes and several parts become easy. In a single thread, the individual instance of node. A developer can access Operating System functionalities by the child_process module, this happens by running any system command inside a child process.

11. How to stop master process without suspending all of its child processes?

Terminated process is said to be a zombie or defunct until the parent does wait on the child. When a process terminates all of the memory and resources associated with it are deallocated so they can be used by other processes.

12. What does emitter do and what is dispatcher?

An Emitter class can be used to raise and handle custom events. It facilitates interaction between objects in Node. A Dispatcher is a service object that is used to ensure that the Event is passed to all relevant Listeners.

13. Since node is a single threaded process, how to make use of all CPUs?

Node JS is one-thread-per-process. If the number of cores is 1, it just simply runs the application as it ran previously. If it has more cores, it detects if the running process is the Master process with the help of cluster module.

It then loops over the number of CPUs of the machine and forks the current process using the cluster. fork() method.

14. List some features of Express JS.

The core features of Express framework:

It can be used to design single-page, multi-page and hybrid web applications.
It allows to setup middlewareresponding to HTTP Requests.
It defines a routing table which is used to perform different actions based on HTTP method and URL.

15. Write the steps for setting up an Express JS application.

Adding dependencies.
First create a directory for your new application and navigate into it.
Use the npminit command to create a package.json file for the application.
Now install Express in the myapp directory and save it in the dependencies list of the package.json file.
npm install express.

16. What do you mean by Express JS?

Express JS is a back end web application framework for Node JS, released as free and open-source software under the MIT License. It is designed for building web applications and APIs. It has been called the de facto standard server framework for Node.

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Cognizant Node JS Interview Questions