Node.js Interview Questions(1)

本是古典何须时尚 2023-10-13 19:13 2阅读 0赞

# 1) What is Node.js? #

*  `Node.js`is == Server-side scripting== which is used to build `scalable programs`.
 *  It is a web application framework `built on Google Chrome's JavaScript Engine`.
 *  It runs within the Node.js runtime on Mac OS, Windows, and Linux with no changes.
 *  This runtime facilitates you to execute a JavaScript code on any machine outside a browser.

# 2) Is Node a single threaded application? #

Yes. Node is `a single-threaded application` with event looping.

# 3) What is the purpose of Node.js? #

These are the following purposes of Node.js:

Real-time web applications  
Network applications  
Distributed systems  
General purpose applications

# 4) What are the advantages of Node.js? #

Following are the main advantages of Node.js:

*  Node.js is asynchronous and event-driven. All APIs of Node.js library are `non-blocking`, and `its server doesn't wait for an API to return data`. It moves to the next API after calling it, and a notification mechanism of `Events of Node.js`responds to the s`erver from the previous API call`.
 *  Node.js is very fast because it builds on `Google Chromes V8 JavaScript engine`. `Its library is very fast in code execution.`
 *  Node.js is single threaded but highly scalable.
 *  Node.js provides a facility of no buffering. `Its application never buffers any data. It outputs the data in chunks`.

# 5) Explain Node.js web application architecture? #

A web application distinguishes into 4 layers:

Client Layer: The Client layer contains`web browsers, mobile browsers or applications`which can `make an HTTP request to the web server`.  
Server Layer: The Server layer contains the `Web server`which can intercept the request made by clients and pass them the response.  
Business Layer: The business layer contains`application server`which is u`tilized by the web server to do required processing.` This layer interacts with the data layer via database or some external programs.  
Data Layer: The Data layer contains `databases or any source of data`.

![在这里插入图片描述][1284b392cc024fcaa7cb4619c164cf88.png]

# 6)What do you understand by the term I/O? #

*  The`term I/O`stands for `input and output`. It is used to`access anything outside of your application.`
 *  The I/O describes any program, operation, or device that transfers data to or from a medium or another medium.
 *  This medium can be a physical device, network, or files within a system.
 *  I/O is loaded into the machine memory to run the program once the application starts.

# 7) How many types of API functions are available in Node.js? #

There are two types of API functions in Node.js:

*  `Asynchronous`, `Non-blocking functions`
 *  `Synchronous`, `Blocking functions`

# 8) What do you understand by the first class function in JavaScript? #

*  When functions are treated like any other variable, then those functions are called `first-class functions`.
 *  Apart from JavaScript, many other programming languages, such as `Scala, Haskell, etc. follow this pattern`.
 *  The first class functions can be passed as a param to another `function (callback)`, or a`function can return another function (higher-order function).`
 *  Some examples of`higher-order functions` that are popularly used are`map() and filter().`

# 9)What is the difference between JavaScript and Node.js? #

![在这里插入图片描述][2ebef85e156942bf812941a4631ce4c9.png]

# 10) Explain the working of Node.js? #

The workflow of a Node.js web server typically looks like the following diagram. Let us see the flow of operations in detail:

![在这里插入图片描述][8f24eeb9241b400ca990c3aab4eaad9f.png]

*  According to the above diagram,`the clients send requests to the webserver to interact with the web application`. These requests can be `non-blocking` or`blocking`and used for querying the data, `deleting data, or updating the data`.
 *  js`receives the incoming requests and adds those to the Event Queue`.
 *  After this step, the requests are `passed one by one through the Event Loop`. It checks if the requests are simple enough not to require any external resources.
 *  The event loop then processes the simple requests`(non-blocking operations), such as I/O Polling, and returns the responses to the corresponding clients.`
 *  `A single thread from the Thread Pool is assigned to a single complex request.` This thread is responsible for completing a particular blocking request by accessing external resources, such as computation, database, file system, etc.
 *  `Once the task is completed, the response is sent to the Event Loop that sends that response back to the client.`

# 11) How can you manage the packages in your Node.js project? #

*  We can manage the packages in our Node.js project by using several package installers and their configuration file accordingly.
 *  Most of them use `npm` or `yarn`. The npm and yarn both`provide almost all libraries of JavaScript with extended features of controlling environment-specific configurations.`
 *  We can use `package.json`and `package-lock.json` to maintain versions of libs being installed in a project. So, there is no issue in porting that app to a different environment.

# 12) Why is Node.js Single-threaded? #

*  Node.js is`a single-threaded application`with `event looping for async processing`.
 *  The biggest advantage of doing async processing on a single thread under typical web loads is that you can `achieve more performance and scalability than the typical thread-based implementation`.

# 13) What do you understand by callback hell in Node.js? #

*  `Callback hell` is `a phenomenon` that creates a lot of problems for a JavaScript developer when he tries to`execute multiple asynchronous operations` one after the other.
 *  A function is called `an asynchronous function` when some external activity must complete before processing a result.
 *  It is called `asynchronous`because there is an unpredictable amount of time before a result becomes available.
 *  These functions require `a callback function` to handle errors and process the result.

# 14) How is Node.js better than other most popular frameworks? #

Based on the following criteria, we can say that Node.js is better than other most popular frameworks:

*  `js makes development simple`because of its`non-blocking I/O a`nd `even-based model.` This simplicity results in short response time and concurrent processing, unlike other frameworks where developers use thread management.
 *  js runs on a`chrome V8 engine` which is written in`C++`. It enhances its performance `highly with constant improvement`.
 *  `With Node.js, we will use JavaScript in both the frontend and backend development that will be much faster`.
 *  js provides ample libraries so that we don’t need to reinvent the wheel.

# 15) In which types of applications is Node.js most frequently used? #

Node.js is most frequently and widely used in the following applications:

`Internet of Things`  
`Real-time collaboration tools`  
`Real-time chats`  
`Complex SPAs (Single-Page Applications)`  
`Streaming applications`  
`Microservices architecture etc.`

# 16) What are some commonly used timing features of Node.js? #

Following is a list of some commonly used timing features of Node.js:

`setTimeout/clearTimeout:`This timing feature of Node.js is used to implement delays in the code execution.  
`setInterval/clearInterval:` The setInterval or clearInterval timing feature is used torun a code block multiple times in the application.  
`setImmediate/clearImmediate:`This timing feature of Node.js is used to set the execution of the code at the end of the event loop cycle.  
`nextTick:`This timing feature sets the execution of code at the beginning of the next event loop cycle.

# 17)What do you understand by the term fork in Node.js? #

*  Generally, `a fork is used to spawn child processes`.
 *  In Node.js, it is used to create a new instance of the V8 engine to `run multiple workers to execute the code.`

# 18) Which is the best tool we can use to assure consistent code style in Node.js? #

`ESLint tool` is one of the best tools we can use with any IDE to ensure a consistent coding style. It also helps in maintaining the codebase.

# 19) What is the main difference between front-end and back-end development? #

The following table specifies the key differences between a front-end and back-end development:

![在这里插入图片描述][328bc6a1d65a44dfbd8c821d0537ea1f.png]

# 20)Give an example to demonstrate how can we use async await in Node.js? #

See the following example of using async-await pattern:

[1284b392cc024fcaa7cb4619c164cf88.png]: https://img-blog.csdnimg.cn/1284b392cc024fcaa7cb4619c164cf88.png
[2ebef85e156942bf812941a4631ce4c9.png]: https://img-blog.csdnimg.cn/2ebef85e156942bf812941a4631ce4c9.png
[8f24eeb9241b400ca990c3aab4eaad9f.png]: https://img-blog.csdnimg.cn/8f24eeb9241b400ca990c3aab4eaad9f.png
[328bc6a1d65a44dfbd8c821d0537ea1f.png]: https://img-blog.csdnimg.cn/328bc6a1d65a44dfbd8c821d0537ea1f.png