Node.js is a JavaScript runtime built on Chrome's V8 JavaScript engine.

How to install

With installer

brew install node

How to use

// index.js

console.log('Hello world!')

$ node index.js
-> Hello world!

$ node --help

In order to get list of available options and basic usage execute:

What Node.js can do?

Web servers
Development tooling
Desktop apps
Command line tools
etc

EcmaScript spec

Host environment

A host environment provides platform-specific objects and functions additional to the language core. Web browsers give a means to control web pages. Node.JS provides server-side features, and so on.

The most common host environment for JavaScript is web browsers. Web browsers typically use the public API to create host objects responsible for reflecting the DOM into JavaScript.

For example:

window
document
addEventListener
removeEventListener
history
etc.

Node.js host environment

global
require
module
__filename
__dirname
process
setTimeout
setInterval
setImmediate
etc.

Modules

require(id)

// Importing a local module:
const myLocalModule = require('./path/myLocalModule');

// Importing a JSON file:
const jsonData = require('./path/filename.json');

// Importing a module from node_modules or Node.js built-in module:
const crypto = require('crypto');

Used to import modules, JSON, and local files. Modules can be imported from node_modules. Local modules and JSON files can be imported using a relative path (e.g. ./, ./foo, ./bar/baz, ../foo).

module.exports

// module B
const config = {
    apiKey: '111-222-333-444'
}

module.exports = config

// module A
const config = require('./config')

console.log(config.apiKey) // 111-222-333-444

Built-in modules

Internal modules overview (fs, http)

fs

The Node.js file system module allows you to work with the file system on your computer.

const fs = require('fs');
const path = require('path');

fs.readFile(__filename, 'utf-8', (err, file) => {});
const file = fs.readFileSync(__filename, 'utf-8');

fs.writeFile(path.join(__dirname, './1.txt'), 'Hello\nWorld\n!', (err) => {});
fs.writeFileSync(path.join(__dirname, './1.txt'), 'Hello\nWorld\n!');

fs.readdir(__dirname, (err, dir) => {});
fs.readdirSync(__dirname);

h ttp

Node.js has a built-in module called HTTP, which allows Node.js to transfer data over the Hyper Text Transfer Protocol (HTTP).

const http = require('http');

const server = http.createServer((request, response) => {
    response.end('Hello world!');
});

server.listen(8080);

Npm - node package manager

Npm is installed alongside with Node.js

$ npm install moduleName

But before we install any module we should create a package.json file

$ npm init

This can be done manually or via

{
  "name": "test",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "keywords": [],
  "author": "",
  "license": "ISC"
}