Introduction to Node JS

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Have a look to the next Node JS tutorial in Youtube: Node JS Tutorial 2023

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Introduction to Node.js (videos from 1-7)

Summary:

• ECMAScript
• Chrome's V8 Engine
• Javascript runtime ( -37)
• Node.js visually and through code
• Hello world program
• Browser vs Node.js

Resume: Important to understand what is Node, where it cames from and how it works.

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Local modules (videos from 8 to 17)

Summary:

• Local modules (9)
• Module scope and export: module.export = { ... } (10-11)
• Module wrapper (IIFE): (function(exports, require, module, __filename, __dirname) { ...code })() (12)
• Module caching: This happens when you export a module as an instance of a class, instead of export the class itself (13)
• Import and export module patterns (module.exports func/class/..., module.exports = () => { ... }, module.exports { ... }, exports.func1; exports.func2;) (14)
• Difference between module.exports and exports: module.exports is the real function and exports is just a memory reference to module.exports (15)
• Explanation of ES Modules: Also for local modules. .mjs as file extension to use ES Modules and the way to use it is by export default or export and import it as import * from './rute' (16) Good to know: .ts files and .tsx files have the ES Modules implemented, but if you want to use this type of module systemusing javascript native code, each file extension should be .mjs

Resume:

1. Each file loaded by Node.js is considered as a module.
2. To include variables, classes and functions from outside a module: a. CommonJS: they have to be implicity exported with module.exports or exports and imported with require(). b. ES Modules: Exported with export default or export and imported with import * from './rute'
3. Watch mode to update the console with each change: node --watch file (17)

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Build-in Modules (18 to 36)

Summary (also summary on video 36 - 2:00)

• Path Module: Utilities to work with files and work directories (19).
• Event Module. Event-driven programing. Example of usage is the html elements events, the event waits to launch the callback until it recieves the action (21).

Extending from EventEmitter. Possible to create a class extending from EventEmitter and use its methods to create events inside the custom class (22)

• Fs Module: Read and write into file synchronously and asynchronously (26)

  How does fs-module work with stream data? (28) Types of streams (28):

  1. Readable streams => Ex: reading from file
  2. Writable streams => Ex: writing to a file
  3. Duplex streams (readable and writable) => Ex: Sockets
  4. Transform streams (modify/transform data while is written/read) => Ex: file comrpession where ayou can write compressed data and read de-compressed data to and from a file as a transform stream.

• Fs Promises Module: Read and write a file synchronously and asynchronously with promises. In terms of performance is better to use fs-module instead of fs-promise-module, but for better code understanding, is better to use the fs-promise-module (27)

• HTTP Module: How does the web work. HTTP (Hypertest Transfer Protocol) explanation (30)

  1. Create an HTTP server in Node.js (31)
  2. JSON Response (32)
  3. HTML Response. Reading an HTML file and return its data. Using of buffer and chunks to updgrade the performance of reading. (33)
  4. HTML Template. In case of adding dynamic variables (34)
  5. HTTP Routing. Request url with ifs and switch (35)
  6. Back-end wen frameworks. Express, Nest, Hapi, ... (36)

Needed knowledge

• Callbacks: Function argument passed to another function function func(callback) { callback(); }. Types of callbacks: syncrhonous callbacks (executed inmidiatly) and asynchronous callbacks (usually used to continue or resume after an asynchronous operation) Node.js have asycrhonoys nature to prevent blocking of execution (20)
• Character sets and encoding. Binary data explanation, character sets and character encoding (23)
• Streams and Buffers (24)

1. Stream: Sequence of data that is being moved from an endpoint to another over the time.
2. Buffer: Incredible example in the video (rollercoaster example => 2:15 - 5:05)

• Asynchronous JavaScript explanation (25-37)
• Streams. Work with data in chunks instead of waiting for the entire data to be availableat once. Do not wait for the entire content (prefered chunks) (28)
• Pipes. Create a pipe between a readable stream and a duplex/transform stream (29)

Resume

1. Use always node: protocol when importing built-in modules

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Libuv dependency (37 to )

Summary

• Libuv (38)

  1. What? Cross platform open source library written in C language.
  2. Why? Handles asynchronous non-blocking operations in Node.js.
  3. How? Using thread pool and event loop.

• Thread pool. Examples to understand libuv's thread pool (39)
• Thread pool size (40).

  • Libuv's thread pool has 4 threads by default.
  • Encrease the thread pool size (Windows via command line with set UV_THREADPOOL_SIZE=5).
  • Speed relation with CPU Cores. Performance is limited by the number of CPU cores.

• Network I/O. Work delegation to the OS Kernel when it is a network input/output process. Also managed by libuv dependency library (41).

Resume