Node.js Flashcards

Question

Fill in the blank: The __________ module allows you to create HTTP servers in Node.js.

Answer 1

To enable Cross-Origin Resource Sharing in web applications.

Answer 2

B) npm install -g

Answer 3

An object that represents the eventual completion or failure of an asynchronous operation.

Answer 4

It runs the script defined in the 'start' property of the package.json file.

Answer 5

event-driven

Answer 6

To load environment variables from a .env file into process.env.

Answer 7

It checks for vulnerabilities in your project's dependencies.

Answer 8

To create child processes that can share server ports.

Answer 9

To parse incoming request bodies in a middleware before your handlers.

Answer 10

C) Both A and B

Answer 11

To provide a schema-based solution for modeling application data with MongoDB.

Answer 12

It sends a JSON response.

Answer 13

To create and verify JSON Web Tokens (JWTs).

Answer 14

B) Multi-threaded

Answer 15

It allows you to write asynchronous code that looks synchronous.

Answer 16

To manage sessions in Express applications.

Answer 17

app.delete()

Answer 18

Cryptographic functionality that includes a set of wrappers for OpenSSL's hash, HMAC, cipher, decipher, sign, and verify functions.

Answer 19

B) Express

Answer 20

To automatically restart the Node.js application when file changes are detected.

Answer 21

It binds and listens for connections on the specified host and port.

Answer 22

To handle multipart/form-data, which is used for uploading files.

Answer 23

C) Both A and B

Answer 24

To create modular, mountable route handlers.

Answer 25

To work with file and directory paths.

Answer 26

To install a package and its dependencies.

Answer 27

C) Both A and B

Answer 28

To validate and sanitize user input.

Answer 29

It redirects the client to a different URL.

Answer 30

error handler

Answer 31

To manage Node.js applications in production.

Answer 32

B) mongoose

Answer 33

To secure Express apps by setting various HTTP headers.

Answer 34

It sends a file as an octet stream.

Answer 35

child_process

Answer 36

To compress HTTP responses to reduce their size.

Answer 37

B) app.use()

Answer 38

It executes a function after a specified delay.

Answer 39

To connect to a MongoDB database.

Answer 40

app.post()

Answer 41

To serve static files such as images, CSS, and JavaScript.

Answer 42

To provide operating system-related utility methods and properties.

Answer 43

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.

Answer 44

Yes. It is released under MIT license and is free to use.

Answer 45

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

Answer 46

These are the following purposes of Node.js: Real-time web applications Network applications Distributed systems General purpose applications

Answer 47

Following are the main advantages of Node.js: Node.js is asynchronous and event-driven. All API?s 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 server from the previous API call. Node.js is very fast because it builds on Google Chrome?s 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.

Answer 48

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 utilized 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.

Answer 49

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.

Answer 50

There are two types of API functions in Node.js: Asynchronous, Non-blocking functions Synchronous, Blocking functions

Answer 51

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().

Answer 52

Last 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.

Answer 53

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.

Answer 54

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.

Answer 55

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.

Answer 56

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 and 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.

Answer 57

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.

Answer 58

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.

Answer 59

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.

Answer 60

In Node.js applications, modules are like JavaScript libraries and include a set of functions. To include a module in a Node.js application, we must use the require() function with the parentheses containing the module's name. Node.js has several modules which are used to provide the basic functionality needed for a web application. Following is a list of some of them:

Answer 61

In general, a buffer is a temporary memory mainly used by the stream to hold on to some data until it is consumed. Buffers are used to represent a fixed-size chunk of memory allocated outside of the V8 JavaScript engine. It can't be resized. It is like an array of integers, which each represents a byte of data. It is implemented by the Node. js Buffer class. Buffers also support legacy encodings like ASCII, utf-8, etc.

Answer 62

Error-first callbacks are used to pass errors and data. If something goes wrong, the programmer has to check the first argument because it is always an error argument. Additional arguments are used to pass data.

Answer 63

All the API's of Node.js library are asynchronous means non-blocking. A Node.js based server never waits for an API to return data. The Node.js server moves to the next API after calling it, and a notification mechanism of Events of Node.js responds to the server for the previous API call.

Answer 64

To avoid callbacks, you can use any one of the following options: You can use modularization. It breaks callbacks into independent functions. You can use promises. You can use yield with Generators and Promises.

Answer 65

Yes, Node.js provides a simple TCP based protocol and built-in debugging client. For debugging your JavaScript file, you can use debug argument followed by the js file name you want to debug.

Answer 66

Control flow function is a generic piece of code that runs in between several asynchronous function calls.

Answer 67

The control flow does the following job: Control the order of execution Collect data Limit concurrency Call the next step in a program

Answer 68

I/O operations Heavy computation Anything requiring blocking

Answer 69

REPL stands for Read Eval Print Loop. It specifies a computer environment like a window console or Unix/Linux shell where you can enter a command, and the computer responds with an output. It is very useful in writing and debugging the codes. REPL environment incorporates Node.js.

Answer 70

Following are the terms used in REPL with their defined tasks: Read: It reads user's input; parse the input into JavaScript data-structure and stores in memory. Eval: It takes and evaluates the data structure. Print: It is used to print the result. Loop: It loops the above command until user press ctrl-c twice to terminate.

Answer 71

Yes. You can evaluate simple expressions using Node REPL.

Answer 72

In REPL, the underscore variable is used to get the last result.

Answer 73

Yes, Node.js Crypto module supports cryptography. It provides cryptographic functionality that includes a set of wrappers for open SSL's hash HMAC, cipher, decipher, sign and verify functions. For example:

Answer 74

npm stands for Node Package Manager. Following are the two main functionalities of npm: Online repositories for node.js packages/modules which are searchable on search.nodejs.org Command line utility to install packages, do version management and dependency management of Node.js packages.

Answer 75

Following is a list of tools that can be used in developing code in teams, to enforce a given style guide and to catch common errors using static analysis. JSLint JSHint ESLint JSCS

Answer 76

Operational errors are not bugs, but create problems with the system like request timeout or hardware failure. On the other hand, programmer errors are actual bugs.

Answer 77

Global installation of dependencies is stored in/npm directory. While local installation of dependencies stores in the local mode. Here local mode refers to the package installation in node_modules directory lying in the folder where Node application is present. Globally deployed packages cannot be imported using require() in Node application directly. On the other hand, locally deployed packages are accessible via require(). To install a Node project globally -g flag is used. C:\Nodejs_WorkSpace>npm install express ?g To install a Node project locally, the syntax is: C:\Nodejs_WorkSpace>npm install express

Answer 78

The Node.js provides Buffer class to store raw data similar to an array of integers but corresponds to a raw memory allocation outside the V8 heap. It is a global class and can be accessed in an application without importing a buffer module. Buffer class is used because pure JavaScript is not compatible with binary data. So, when dealing with TCP streams or the file system, it's necessary to handle octet streams.

Answer 79

The Node.js Assert is a way to write tests. It provides no feedback when running your test unless one fails. The assert module provides a simple set of assertion tests that can be used to test invariants. The module is intended for internal use by Node.js, but can be used in application code via require ('assert'). For example:

Answer 80

The Streams are the objects that facilitate you to read data from a source and write data to a destination. There are four types of streams in Node.js: Readable: This stream is used for reading operations. Writable: This stream is used for write operations. Duplex: This stream can be used for both reading and write operations. Transform: It is a type of duplex stream where the output computes according to input.

Answer 81

In Node.js, event-driven programming means as soon as Node starts its server, it initiates its variables, declares functions and then waits for an event to occur. It is one of the reasons why Node.js is pretty fast compared to other similar technologies.

Answer 82

Although, Events and Callbacks look similar the differences lies in the fact that callback functions are called when an asynchronous function returns its result whereas event handling works on the observer pattern. Whenever an event gets fired, its listener function starts executing. Node.js has multiple in-built events available through the events module and EventEmitter class which is used to bind events and event listeners.

Answer 83

The Punycode is an encoding syntax which is used to convert Unicode (UTF-8) string of characters to ASCII string of characters. It is bundled with Node.js v0.6.2 and later versions. If you want to use it with other Node.js versions, then use npm to install Punycode module first. You have to used require ('Punycode') to access it.

Answer 84

The Node.js TTY module contains tty.ReadStream and tty.WriteStream classes. In most cases, there is no need to use this module directly. You have to used require ('tty') to access this module.

Answer 85

The most crucial difference between operational and programmer errors is that the operational errors are not bugs but problems with the system such as to request timeout or hardware failure. On the other hand, the programmer errors are actual bugs in the application.

Answer 86

In Node.js, there are two ways to read and execute files: readFile and CreateStream. The readFile() process is a fully buffered process that returns the response only when the complete file is pushed into the buffer and is read. This process is called a memory-intensive process, and in the case of large files, the processing can be very slow. On the other hand, the createReadStream() is a partially buffered process that treats the entire process as an event series. The entire file is split into chunks and then processed and sent back as a response one by one. After completing this step, they are finally removed from the buffer. Unlike the readFile process, the createReadStream process is effective for the processing of large files.

Answer 87

In Node.js, the concept of Punycode is used for converting one type of string into another type. Punycode is an encoding syntax used for converting Unicode (UTF-8) string of characters into a basic ASCII string of characters. Now, the hostnames can only understand the ASCII characters so, after the Node.js version 0.6.2 onwards, it was bundled up with the default Node package. To use it with any previous versions, you have to use the following code: punycode = require('punycode');

Answer 88

Just because the Node.js applications run on a single processor, they don't take advantage of a multiple-core system by default. Clustering is used to overcome this issue. The cluster mode is used to start up multiple node.js processes, thereby having multiple instances of the event loop. When we start using clusters in a Node.js app, it creates multiple node.js processes. But there is also a parent process called the cluster manager, which is responsible for monitoring the health of the individual instances of the application.