Node JS

Question 1

What is Node JS?

Answer 1

A cross-platform JavaScript runtime environment to build fast and scalable server-side applications. It embeds and adds additional functionality over Google Chrome’s V8 JavaScript engine. Node uses one main thread. It also uses events to sync states.

Question 2

node.js cheetsheet

Answer 2

https://www.codecademy.com/learn/learn-node-js/modules/intro-to-node-js/cheatsheet

Question 3

npm init

Answer 3

A command to create a Node.js project. This creates the package.json and gives you step-by-step prompts.

Use “npm init -y” to keep everything default.

Question 4

npm

Answer 4

Allows you to download remote packages and manage them via terminal. It is a library and registry for JS software packages. It is the most popular package manager. It allows you to re-use your code in other projects, use other developer’s code, and share your solutions to other developers.

Question 5

npm install

Answer 5

used to install dependencies from the package.json file.

-use “npm i PACKAGE_NAME” to install the dependency only on the current project.
-use “npm install -g PACKAGE_NAME” to install the dependency globally to be used in any project.
-use “npm i PACKAGE_NAME” with “-D” or “–save-dev” flag to install a package as a dev dependency.

Question 6

npm start

Answer 6

starts the application.

Question 7

How to quit the application?

Answer 7

On the active session, hold Ctrl+c.

Question 8

setImmediate(functionToExecute)

Answer 8

A function used to execute a function right after the current event loop finishes. Essentially the functionToExecute is called after all the statements in the script are executed.

Question 9

fs

Answer 9

A module responsible for all the async or sync file I/O operations.

Question 10

fs.readFile()

Answer 10

A method used to read files on your computer.

Question 11

require(“module_name”)

Answer 11

A function used to load and cache JavaScript modules. You can use destructuring if you only want to access specific objects or functions from an imported module.

The require function returns module.exports.

Question 12

REPL

Answer 12

Read, Evaluate, Print, and Loop. To use REPL, type “node” and press [enter]. This is a quick way to test simple JavaScript code.

Question 13

core modules

Answer 13

Core modules are built into Node.js environment. Some of the core modules are in the global scope so you do not need to require() them. Other core modules will need the require() function.

Question 14

custom modules

Answer 14

custom modules are imported using require(“./xxxx”) and a specified file path.

Question 15

process module

Answer 15

a global module that gives access to information about the Node.js runtime environment.

Question 16

console module

Answer 16

exports a global console object allowing the terminal to act as a debugging console.

Question 17

path module

Answer 17

a global module that provides utilities for working with file and directory paths.

Question 18

util module

Answer 18

contains methods used to maintain and debug your code.

util.promisify() - takes an input for the function and returns them as a promise.

Question 19

os module

Answer 19

provides methods to retrieve information about the computer, OS, and network interfaces.

Question 20

fs module

Answer 20

a global module allowing you to work with your file system.

Question 21

http module

Answer 21

a global module that creates an HTTP server that listens to server ports and gives a response back to the client.

Question 22

package

Answer 22

a third-party module wrapped up with the list of that module’s own dependencies.

Question 23

package.json

Answer 23

A manifest file containing metadata about a project and it’s dependencies.

• The “dependencies” list all the project’s dependencies alongside their version numbers. “devDependencies” indicates that packages are being used specifically for development.
• Anyone who wants to work with you on your project can download your package.json file and run “npm i”. This will install the listed dependencies they can use.

Question 24

express js

Answer 24

a web application framework for Node.js that helps simplify the process of building web applications. It provides a set of tools and features for creating APIs, web servers, and web applications.

Question 25

node modules with require, exports, and imports

Answer 25

https://adrianmejia.com/getting-started-with-node-js-modules-require-exports-imports-npm-and-beyond/

module.export starts off as an empty object.

Question 26

revealing module pattern

Answer 26

A design pattern where we only want to expose the properties and methods needed via a returned object.

example:
var data = “123”

function showData() {
return data;
}
// here only the function is accessible.
module.exports = showData;

Question 27

when code is ran through Node…

Answer 27

The code is wrapped in an IIFE, giving us access to the module object, require, etc. :
(function (exports, require, module, __filename, __dirname) {
// our code here
var greet = function() {
console.log(“Hello”);
}
module.exports = greet;
}

Question 28

module.exports vs exports

Answer 28

https://stackoverflow.com/questions/16383795/difference-between-module-exports-and-exports-in-the-commonjs-module-system

Question 29

event emitter

Answer 29

an object that can emit named events, which can be listened to by registered listeners. When an event is emitted, all listeners are invoked.

example:
const EventEmitter = require(“events”);
EventEmitter.on(“listen”, () => {
console.log(“hello”)
})
EventEmitter.emit(“listen”);

Question 30

module, package, dependency

Answer 30

Pretty much interchangeable terms to describe re-usable code.

Question 31

nodemon (3rd party module)

Answer 31

a tool that helps develop Node.js based applications by automatically restarting the node application when a file change in the directory is detected.

Question 32

how to uninstall a node module

Answer 32

“npm uninstall PACKAGE_NAME”.

To uninstall all modules, delete the node_modules directory and delete the package-lock.json file.

Question 33

streams

Answer 33

objects that let you read data from a source or write data to a destination in a continuous fashion.